Spring 11 N: Controlling and characterising the structure...

Spring 11 N: Controlling and characterising the structure of organic semiconductorfilms

Key to the development of organic semiconductor technology is the ability to control filmmicrostructure. As control of microstructure can only be achieved if we can also characterisemicrostructure, this symposium seeks to bring together experts in the device-making and structuralcharacterisation communities to address this challenging issue.

Scope:

The performance of organic electronic devices is highly sensitive to the structure of the activeorganic semiconductor layer(s). The structure of organic semiconductor films is in turn highlycomplicated, being in general neither wholly amorphous nor wholly crystalline. Dual challenges inthe development of organic semiconductor technology are the ability to control and characterisefilm microstructure.

Organic semiconductor films are in general processed either through solution or vacuum deposition.The former offers obvious advantages for manufacturing but typically comes at a cost of higherstructural disorder. Vacuum deposition on the other hand offers the ability to create well definedand ordered structures which are necessary for understanding the fundamental properties oforganic semiconductors. Significant advances have been made recently, however, in the ability tocontrol the structure of solution-processed films and will be one of the focuses of this symposium.

For both solution- and vacuum-processed films a detailed knowledge of thin film structure isrequired. Due to the complexity of organic thin films, specialist techniques are required to fullydetermine their structure, especially on the length scales relevant to device performance. It is oftenbeyond the scope of the device scientist to also master these techniques, however thosecharacterising thin film structure also need to ensure they are addressing technologically relevantproblems.

This symposium is aimed to bring together scientists with expertise in the areas of deviceengineering, structural characterisation and semiconductor physics. The symposium will addressstructural issues pertaining to the performance of devices including (but not limited to) organic solarcells, field-effect transistors (FETs) and light-emitting diodes (LEDs), as well structural issuesrelating to our understanding of key semiconductor processes such as charge injection andtransport. Both small molecule and polymeric materials will be covered, along with solution- andvacuum-based deposition methods.

The proceedings of this symposium will be published in the journal Synthetic Materials byElsevier.

Hot topics to be covered by the symposium:

Controlling and characterising the organisation of the active layer in 1-, 2- and 3-dimensionsIn-situ characterisation and modelling of organic film growthUnderstanding the functionality of nanostructureMorphology of bulk-heterojunction solar cells (joint with OPV symposium)Interface structure of organic FETsAdvanced and nanofunctional imagingFilm structure and charge transport

Confirmed list of invited speakers/talks:

F. Biscarini (CNR Bologna) Real-time in-situ electrical and structural characterisationM. Chabinyc (UCSC USA) Topic TBCK. Cho (Pohang U. of Science and Technology) Control of morphology for high performance OFETsJ. Cornil (U. Mons) Modelling charge transport in organic semiconductorsM. Fahlman (Linkoping University, Sweden) Energy Level Alignment at Organic-organic and Hybridorganic HeterojunctionsD. Ginger (U. Washington USA, joint with symposium S) Nanofunctional imaging of polymer solarcellsN. Greenham (Cambridge University, UK, joint with symposium S) Topic TBCM. Heeney (Imperial College London) Synthesis of highly ordered polymers for OFETsN. Koch (Humboldt-U. zu Berlin) Surface physics of small molecule thin filmsP. Puschnig (U. Leoben) Modelling the organic thin film growth of rod-like pi-conjugated moleculesP. Rudolf (U. Groningen) Sub-monolayer formation of pentacene thin filmsA. Salleo (Stanford U.) Microstructure/Charge Transport RelationshipsP. Samori (U. Strasbourg, joint with Symposium G) Supramolecular self-assembly for the creationof nanostructured devices

EMRS - Strasbourg - Spring 11 N: Controlling and characterising the str... http://www.emrs-strasbourg.com/index2.php?option=com_content&tas...

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A. Sassella (University of Milano-Bicocca) Growing Epitaxial Heterostructures of OrganicSemiconductorsF. Schreiber (U. Tübingen, joint with symposium M) In-situ characterisation of organic thin filmsgrowthM. Thelakkat (U. Bayreuth, joint with symposium S) Block copolymers for OPVsM. Toney (SSRL USA, joint with symposium S) In situ grazing incidence x-ray scattering ofpolymer/fullerene blends

Scientific Advisory Committee:

H. Ade (USA)F. Cacialli (UK)M. Chabinyc (USA)P. Dastoor (Australia)P. Ho (Singapore)J.-S. Kim (UK)D. Lidzey (UK)P. Müller-Buschbaum (Germany)H. Sirringhaus (UK)S. Tautz (Germany)H. Yoshida (Japan)X. Yang (China)

Proceedings:

Attendees are encouraged to submit a manuscript to the proceedings that will be peer reviewed andpublished in Synthetic Metals. More details to follow.

Graduate student awards (GSA):

A 450€ cash prize and diploma will be awarded in recognition of academic achievement andresearch excellence. For more details and how to apply please see: http://www.emrs-strasbourg.com/index.php?option=com_content&task=blogcategory&id=8&Itemid=25

Sponsors:


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Symposium organizers:

Chris McNeillDepartment of Materials EngineeringMonash UniversityClayton, VIC 3800AustraliaTel: +61 3 9902 4896Fax:+61 3 9905 [email protected]

Roland ReselInstitute of Solid State PhysicsGraz University of TechnologyPetersgasse 16A-8010 GrazAustriaTel: +43 316 873 8476Fax:+43 316 873 [email protected]: www.if.tugraz.at/users/resel/

Joachim LoosSchool of Physics & AstronomyUniversity of GlasgowG12 8QQUnited KingdomTel: +44 (0)141 330 3019Fax: +44 (0)141 330 [email protected]

Martin BrinkmannInstitut Charles Sadron CNRS23 rue du Loess67034 StrasbourgFranceTel: +33 (0)3 88 41 40 47Fax:+33 (0)3 88 41 40 [email protected]

Michael RamseyInstitute of PhysicsKarl-Franzens UniversityUniversitätsplatz 3A-8010 GrazAustriaTel: +43 316 380 5203Fax:+43 316 380 [email protected]


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PROGRAM VIEW : 2011 Spring & Bilateral

MY PROGRAM : 2011 Spring & Bilateral

Controlling and characterising the structure of organic semiconductor films

start at Subject Num.

Interfaces and Energetics I : Chris McNeill

09:00 INVITED: Structure and electronic properties of hybrid organic/inorganic interfacesAuthors : Norbert Koch*, Humboldt-Universität zu Berlin, Institut für Physik, Brook-Taylor Str. 6,12489 Berlin, GermanyResume : The energy level alignment at ubiquitous organic/inorganic interfaces in opto-electronicdevices directly impacts functionality and efficiency. For instance, the energy difference betweenthe Fermi-level of an electrode and the charge transport levels of an organic semiconductor affectsthe operation voltage of light emitting diodes, and the relative alignment of valence/conductionband edges of an inorganic semiconductor and the highest occupied/lowest unoccupied levels of anorganic counterpart determines whether charge- or energy-transfer across such a hybrid interfaceoccurs. Reliable predictions on the energy levels at such interfaces require exact knowledge oftheir structure. The anisotropic nature of organic materials can result in complex thin-film growth,involving molecular reorientation that may depend on the atomic structure of an inorganicsubstrate and surface molecule density. Examples for organic/metal and organic/inorganicsemiconductor interfaces will be discussed, where structural changes of the organic layer modifythe interface electronic properties. Molecular orientation dependent variations of the interfacialenergy levels over more than 1 eV can be understood by taking into account intramoleculardipoles and conformation dependent hybridization of molecular orbitals and inorganicsemiconductor or metal bands.

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09:30 Core-energy level difference in the surface and bulk regions of organic semiconductor films studiedby X-ray photoemission spectroscopy with depth resolutionAuthors : Hiroyuki Yoshida* (1,2), Eisuke Ito (3), Masahiko Hara(3), Naoki Sato (1) 1 KyotoUniversity, Japan 2 PRESTO Japan Science and Technology Agency 3 RIKEN, JapanResume : Ionization energy (IE) is a fundamental physical parameter which is in many casesmost accurately determined by photoemission spectroscopy (PES). For organic semiconductormaterials, however, there has been for decades an argument regarding the determination of IEwhether the onset or maximum of the peak of PES are used as the position of the valence band. Itwas believed that IE derived from the onset of the peak corresponds to the bulk value because IEis lower in the bulk than in the surface. Recently, however, it was reported that the energy levelsare the same between the bulk and the surface. We have developed a new experimentaltechnique to examine the core energy levels with depth resolution; energy profile of angle-resolved X-ray photoemission spectra (XPS) is precisely analyzed using target factor analysis toobtain energy levels of core-electrons as a function of depth. In this work we examine thedifference in core-energy levels between the surface and bulk of organic semiconductor materialsusing our new method which provides much more quantitative analysis than earlier works. Theresults show that the core-levels of the first surface layer are different from those of the bulk byan amount ranging from 0.2 to 0.4 eV. By comparing the values of different organic materialssystematically, e.g. with and without permanent dipole moment, the origin of the energydifference will be discussed.

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09:45 Alkali metal doping of molecular thin films: a momentum space viewAuthors : G. Koller*1, P. Puschnig2, E. Reinisch1, M. Ostler3, T. Ules1, S. Berkebile1, C. Ambrosch-Draxl2, T. Seyller3, M.G. Ramsey1 1 Institute of Physics, University of Graz, A-8010 Graz, Austria2 Atomistic Modelling and Design of Materials, University of Leoben, 8700 Leoben, Austria. 3Technische Physik, University Erlangen Nurnberg, D-91058 Erlangen, GermanyResume : Upon alkali metal doping of organic semiconducting molecules gap states, polarons andbipolarons, are induced, which are thought to facilitate the enhanced conductivities. The dopinginduced modifications of the molecular electronic structure can be investigated by probing theirmomentum resolved electronic band structure and comparing these to state of the art DFTcalculations. This in turn requires highly ordered films and monolayers. Here, we show that thatuniaxially oriented molecular films can be doped with the order being maintained. Specifically,with band and 2D momentum maps we followed the electronic processes occurring upon alkalimetal doping of a highly ordered monolayers and thin films of sexiphenyl (6P) and pentacene (5A)grown on Cu(110) for increasing amounts of Cesium. The doping of a 6P monolayer on Cuproceeds via two regimes. In a first step Cs lifts the hybridization of the 6P monolayer with Cu. Onincreasing this Cs dose bipolaronic states are observed, whose distinct 2D momentum spacedistribution allows them to be identified. Supported by the Austrian Science Funds FWF(P21330-N20). We acknowledge the HZB Berlin - BESSY II for provision of synchrotron radiation atbeamline TGM 4 and funding from the European Community's Prog. (FP7/2007-2013) grant

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10:00 Coffee break

Interfaces and Energetics II : Jérôme Cornil

10:30 INVITED: Energy Level Alignment at Organic-organic and Hybrid organic Heterojunctions: Inter-and Intra-molecular Order and Electrostatic EffectsAuthors : Mattias Andersson, Slawomir Braun, Linda Lindell, Parisa Sehati and Mats Fahlman*Department of Physics, Chemistry and Biology, Linkoping University 58183 Linkoping, SwedenResume : Organic electronic devices such as solar cells, light-emitting diodes and field-effecttransistors are multi-layered devices where their ultimate performance is to a large extentdominated by the electronic processes at interfaces. The relative position of energy levels across astack of thin organic layers is important for charge injection/separation and hence for deviceengineering and optimization. For organic photovoltaic devices, the donor-acceptor interaction is ofparticular importance as it strongly effects not only the efficiency exciton dissociation and chargeseparation but also the size of the open circuit voltage. Experimental results obtained on variousorganic-organic semiconductor hetero-junctions show that the behavior of specific organic hetero-junctions can be predicted by the Integer Charge Transfer (ICT) model [1-3] using values of theinteger charge transfer states (EICT+, EICT-) as measured by ultraviolet photoelectronspectroscopy (UPS). The integer charge transfer state energies, EICT+ (EICT-) represent thelowest energy required to oxidize (the largest energy gained upon reducing) the organic moleculeat an interface [4]. Here we will present the latest results on the ICT model. In particular usingpoly(3-hexylthiophene) (P3HT) and (6,6)-phenyl-C61-butyric-acid (PCBM), we explore the effectsof inter- and intra-molecular order at the interface and the electrostatic interaction with thesubstrate on the EICT+,-, and give examples of on how they effect exciton dissociation and chargetransport. References [1] C. Tengstedt, W. Osikowicz, W.R. Salaneck, I.D. Parker, C-H. Hsu and M.Fahlman, Appl. Phys. Lett. 88 (2006) 053502. [2] M. Fahlman, A. Crispin, X. Crispin, S.K.M.Henze, M.P. de Jong, W. Osikowicz, C. Tengstedt and W.R. Salaneck, J. Phys.: Condens. Matter 19(2007) 183202. [3] S. Braun, W. R. Salaneck and M. Fahlman, Adv. Mater. 21 (2009) 1450. [4] P.Sehati, S. Braun, L. Lindell, X. Liu, L.M. Andersson and M. Fahlman, IEEE J. Sel. Top. QuantumElectron., 16 (2010) 1718.

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11:00 Layer Inversion in Organic HeterostructuresAuthors : L.D. Sun*, C.Y. Liu, D. Queteschiner, G. Weidlinger and P. Zeppenfeld Institute ofExperimental Physics, Johannes Kepler University Linz Altenbergerstr. 69, A-4040 Linz AustriaResume : Thermally activated inversion of pentacene/para-sexiphenyl (p-6P) organicheterostructures on the Cu(110) surface is studied with the combination of reflectance differencespectroscopy (RDS) and scanning tunnelling microscopy (STM). The heterostructures are formedby deposition of a sub-monolayer of pentacene on top of a well ordered p-6P buffer layer with athickness of up to 3 monolayers on Cu(110) at 15 K. When the sample temperature is raised,these heterostructures invert, with pentacene molecules diffusing through the p-6P buffer layerand getting in direct contact with the substrate. The observed inversion is due to the energyminimization of the multilayer system. The onset temperature of the inversion increases with thethickness of p-6P layers indicating a corresponding rise of the energetic barrier for the inter-layerdiffusion.

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11:15 How to Control Band Bending like Behavior at Organic InterfacesAuthors : A. Schöll*1, M. Häming1, M. Greif1, C. Sauer1, and F. Reinert1,2 1Experimentelle PhysikVII und Röntgen Research Center for Complex Materials (RCCM), Universität Würzburg, 97074Würzburg, Germany 2Karlsruher Institut für Technologie (KIT), Gemeinschaftslabor fürNanoanalytik, 76021 Karlsruhe, GermanyResume : Many studies of organic-metal and organic-organic interfaces have focused on thealignment of the electronic levels, since they determine charge injection. The role of chargetransfer at the interface, space charges, defects, dopants and surface or interface dipoles havebeen discussed as well as the alignment of vacuum- or charge neutrality levels. However, thefundamental mechanisms are still not clear. Hence structurally well defined model systems, whichallow a systematic and detailed investigation of the interface characteristics are very important.Ultrathin SnPc/PTCDA/Ag(111) and SnPc/Ag(111) films can provide such well defined interfaces[1,2] and thus allow a very precise analysis of the electronic structure with photoelectronspectroscopy. The interaction between first and second adsorbate layer is weak and non covalentand charge transfer can be neglected. Moreover, a coverage dependent rigid level shift is observedfor the SnPc spectra of the hetero-molecular film, in analogy to the band bending occurring atSchottky contacts. We demonstrate that the built-in electric field at the interface can be explainedby the formation of an interface dipole, which induces a dipole field and thus extends over severaladsorbate layers [3]. Moreover, the comparison with SnPc/Ag(111) indicates that the induceddipole field can be controlled by the interlayer. [1] M. Häming et al, JESRP 174 (2009) [2] M.Häming et al, Surf. Sci. 604 (2010) [3] M. Häming et al, PRB 82 (2010)

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11:30 Recent advances in making and characterising Ohmic contactsAuthors : R.Q. Png*,(a) J.H. Burroughes,(c) Richard Friend,(a,d) L.L. Chua,(b,a,d) P.K.H. Ho (a)Affiliations: (a) Dept of Physics, (b) Dept of Chemistry, National University of Singapore; (c)Cambridge Display Technology, Cambridge; (d) Cavendish Laboratory, University of CambridgeResume : The ability to fabricate Ohmic contacts at will to organic semiconductors (OSCs), suchas for hole injection into deep ionization-potential (Ip) OSCs is critical to achieving high energyefficiency and stability not only in OSC devices, but also a wide variety of carbon nanotube and

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quantum dot devices. Significant progress has been made in the field largely by trial-and-error.Recently, we have developed a versatile nitrene chemistry for photocrosslinking polymer thinfilms. Using this platform, we show that solution-processed air-stable hole-injection layers can befabricated to achieve Ohmic hole injection into poly(fluorene), a model deep-Ip OSC (Ip = 5.85eV). We have systematically characterised the contact energetics by a combination of thin-filmultraviolet photoemission spectroscopy, device electromodulated absorption spectroscopy anddevice current-voltage measurements. The results reveal several surprising features, including: (i)The previous notion that the device built-in potential should level off once the electrodework-function crosses the ultraviolet photoemission Fermi-level pinning threshold is incorrect; and(ii) The previous notion that Ohmicity of the contact is simply determined by the energy gapbetween the electrode Fermi level and the OSC transport edge is also incorrect. We will alsodiscuss the corrections to these notions.

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11:45 Energy-level alignment of transition metal oxides and organic semiconductorsAuthors : Mark T. Greiner*, University of Toronto, Department of Materials Science andEngineering Michael G. Helander, University of Toronto, Department of Materials Science andEngineering Zhibin Wang, University of Toronto, Department of Materials Science and EngineeringProf. Zheng-Hong Lu, University of Toronto, Department of Materials Science and EngineeringResume : Several transition metal oxides are known to have favorable energy-level alignmentwith organic semiconductors. The relationship between oxide properties (such as defect states,work function and oxidation state) and energy-level alignment are not yet fully realized. We haveexamined correlations between the oxide properties of several transition metal oxides and theenergy-level alignment of several organic semiconductors. In this presentation we willdemonstrate these correlations and discuss their origins.

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12:00 Probing the organisation and interfacial structure of organic semiconducting thin filmsAuthors : J.P. de Silva*(1), N. Boucher(1), A. Moser(2), R. Resel(2), Y.H. Geerts(3), M.Sferrazza(1) (1) Departement de Physique, Universite libre de Bruxelles, CP223 bld. du Triomphe,B-1050 Brussels, Belgium (2) Institut fuer Festkoerperphysik, Petersgasse 16, 8010 Graz, Austria(3) Laboratoire de Chimie des Polymeres, Universite libre de Bruxelles, CP206/01 bld. duTriomphe, B-1050 Brussels, BelgiumResume : We have explored the molecular organisation and interfacial structure in thin films ofnovel, organic semiconducting material, with a view towards advancing the understanding ofinterfacial structure in such organic semiconducting thin films. If the wide-scale production ofefficient organic thin film devices such as organic light emitting diodes and field effect transistors(OLEDs and OFETs) is to be realised, one of the crucial aspects governing device functionality is thestructure of the principle charge transport interfaces between the component layers. Thedisubstituted oligothiophene derivatives synthesised and examined here-specificallydioctylterthiophene (DOTT)-form various smectic mesophases that may be useful for optimisedcharge transport, through the assembly of self-healing planar charge transport pathways. In thinfilm form, we observe from in-house X-ray and synchrotron grazing incidence diffraction data asubstrate induced, thermodynamically stable ‘thin film’ phase (the existence of which does notdepend on factors such as deposition kinetics for example) within the first few molecular layers atthe substrate interface, which is shown in thicker layers to coexist with the bulk-like smectic filmabove. We also exploit neutron reflectivity to successfully probe the molecular order and interfacialstructure for thin layers of fully deuterated DOTT at the all-important buried semiconductor-dielectric interface that controls charge transport characteristics.

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12:15 Characterisation of conjugated polymer interfaces by off specular neutron scatteringAuthors : David James*, Anthony M. Higgins, Paul Rees, Rowan M. Brown (Swansea University,Singleton Park, Swansea, SA2 8PP, UK) Mark Geoghegan (The University of Sheffield, Western,Bank, Sheffield S10 2TN, UK) Robert Cubitt (Institut Laue-Langevin, BP 156,6, rue Jules Horowitz,38042 Grenoble Cedex 9, France)Resume : Neutron reflectivity offers the opportunity for non-destructive characterisation of buriedpolymer interfaces. To date, we have used specular neutron reflectivity to characterise thestructure of conjugated polymer interfaces found in LEDs [Adv. Funct. Mater. (2009) 19, 157-163]and FETs [Soft Matter (2008) 4, 2220-2224]. However, detecting specularly reflected neutrons onlyallows us to measure the root-mean-square (rms) roughness of the interface averaged over amacroscopic lateral distance. There are two contributions to the rms roughness of a polymer-polymer interface; i) the so-called ‘intrinsic interfacial width’ due to mixing of the polymers at amolecular level and ii) lateral roughness due to deviations of the interface position from the planeof the substrate. Here we present recent work in which we have collected both specular andoff-specular neutrons, allowing us to probe structure in the plane of the interface and to distinguishintrinsic interfacial broadening from longer wavelength lateral roughness. We model theoff-specular scattering using the Distorted Wave Born Approximation (DWBA) [Phys. Rev. B (1988)30, 2297-2311]. In this work we investigate a model conjugated polymer/amorphous polymerinterface (poly(9,9-dioctylfluorene (F8) on deuterated PMMA). We examine the structure of thisinterface by systematically varying the film thickness, which strongly impacts on the amplitude ofthe lateral interface roughness, and allows a more complete analysis of the relative contributionsof intrinsic mixing and lateral roughness. For comparison we also perform off-specularmeasurements on an amorphous (PMMA/polystyrene) interface, which has been studied previouslyusing specular reflectivity and self-consistent-field-theory.

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12:30 Lunch

Control of Structure Through Processing : Martin Heeney


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14:00 INVITED: Control of Morphology and Ordering of Organic Semiconductors for High PerformanceOrganic TransistorsAuthors : Kilwon Cho*, Dept. of Chemical Engineering, Pohang University of Science andTechnology (POSTECH), Pohang, 790-784, KoreaResume : The morphology and ordering of organic semiconductors and characteristics of theinterface between the organic semiconductor and the gate dielectric are crucial determinants ofdevice performance of OFETs. This talk describes our research in this area, and highlights (1) themorphology and molecular orientation of inkjet-printed organic semiconductor, (2) the control ofthe molecular ordering and film morphology of organic semiconductors nearsemiconductor/dielectric interfaces, and (3) fabricating unique structures and morphology oforganic semiconductor/insulating polymer blends such as vertically phase-separated structure andinterconnected semiconducting nanowires embedded in insulating polymer.

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14:30 Surface-Directed Spinodal Decomposition of Solvent-Quenched Organic Semiconductor BlendsAuthors : Jasper J. Michels* Holst Centre/TNO High Tech Campus 31 5656 AE Eindhoven TheNetherlands email: [email protected] tel: +31 (0)40 4020508Resume : Electronic systems based on organic materials often rely on functionalities, uniquelyobtained by controlled nano- or micro-phase separation of two components having markedlydifferent electronic and/or optical properties. Depending on the operational characteristics of thedevice, a layered, pillared or inter-percolating phase morphology is required. This paper describesthe application of a combination of Flory-Huggins and diffuse interface theories to modelmicrostructure evolution in solution-processed layers of organic semiconductor blends, as used inorganic electronics devices.[1] The work considers phase separation of the active blendcomponents of organic transistors based on triisopropylsilylpentacene (TIPS) and poly(alpha-methyl styrene) (PaMS). It is shown that the vertically phase separated structure observed inas-cast blend layers containing a sufficiently high molecular weight PaMS evolves via surface-directed spinodal decomposition. The surface directed effect can already be triggered by smalldifferences in interface interaction energies of the separating phases. During phase separation,which commences at the substrate and air interfaces, bulk features of the TIPS-enriched phaseformed by thermal noise collapse to give the experimentally observed lateral TIPS-PaMS-TIPSmorphology. The reported near absence of phase separation of as-cast blend layers containing alow molecular weight PaMS is reproduced as well. [1] J.J. Michels, ChemPhysChem 2011, in press

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14:45 Morphology control of solution processed small molecule organic semiconductors for large areaorganic electronicsAuthors : Charlotte Kjellander*1, Wiljan Smaal1, Xiaoran Li1,2, Bas van der Putten1, GerwinGelinck1 1 Holst Centre, TNO, High Tech Campus 31, 5656 AE Eindhoven, The Netherlands([email protected]) 2 Department of Chemical Engineering and Chemistry, EindhovenUniversity of Technology, P.O. Box 513, Eindhoven 5600 MB, The NetherlandsResume : Organic electronics is a fast developing field aiming at light-weight, low-cost and largearea applicability. Control of morphology and directionality of the organic semiconductor (OSC)crystals are required to fabricate high performance transistors. We found that the key to achieveuniform crystal morphology over large areas is to control the film formation speed. Dipcoatingexperiments with TIPS-PEN show, with decreasing drying speed, randomly oriented smallcrystallites, needle-shaped crystals and large platelets. The needle morphology is the mostuniformed aligned morphology with the preferred a-axis for electrical transport parallel with thecoating direction. Inkjet printing (IJP) is one of the most promising methods for controlleddeposition of small amounts of OSCs. Spreading of the ink can be controlled by printing on a thinabsorbing polymer layer covering the device substrate. Effectively a blend of polymer and OSC isformed, followed by crystallization upon drying. From literature we know that high Mw polymersfavor lateral phase separation. Surprisingly we observe significantly better transistor performancewith low Mw polymers: TIPS-PEN mobility increases from 0.2 to >1 cm2/Vs. Optimizedconcentration and IJP conditions show controlled film formation of crystal needles growing fromthe contact line to the centre of the deposit. Structural and electronic analyses teach us how tooptimize the device layout for an optimal transistor performance.

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15:00 Controlled nucleation behavior at the solid-liquid interface improves carrier transport in polymerfield-effect transistors.Authors : R. Li(1), H. H. Fong(1), K. Zhao(1), D.-M. Smilgies(2), A. Amassian*(1) (1) MaterialsScience and Engineering, Division of Physical Sciences and Engineering, King Abdullah University ofScience and Technology (KAUST), Thuwal, Saudi Arabia (2) Cornell High Energy SynchrotronSource, Ithaca, NY, USAResume : Low-cost solution processes are deemed to be crucial to the future commercial successof organic electronics. As such, solution processing of polymers deserves special attention andin-depth investigation. As the liquid environment does not lend itself well to in situ probing viatraditional surface science tools, we have developed alternative strategies to simultaneouslymonitor the formation of the thin film and the state of the solute in situ and in real time. This waspossible by combining powerful techniques such as fast, in situ optical reflectometry, withtraditional quartz crystal microbalance technique, and grazing incidence X-ray scattering, thusgaining unprecedented insight into mechanisms and kinetics of solvent drying, polymer nucleation,crystallization, and ultimately into thin film formation. Our results provide new insights into theformation of poly-3(hexylthiophene) thin films via drop- and spin-coating. Importantly, wedemonstrate that polymers tend to undergo heterogeneous nucleation at the solid-liquid interfacewell before the solvent has evaporated, resulting in formation of a well-ordered seed layer. Thisseed layer plays a crucial role in carrier transport; its formation depends upon thermodynamic and

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kinetic considerations, including surface termination, solubility, and process kinetics. Importantly,carrier transport in polymer OTFTs is shown to depend strongly upon the characteristics of the seedlayer.

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15:15 Vapour printing as means to spatially control the microstructure in organic semiconductorsAuthors : M. Campoy-Quiles*, D. Nassyrov, I. Burgu? M. Schmidt, M. Garriga, I. Alonso, and A. R.Go? Science Material Institute of Barcelona (ICMAB-CSIC), Campus UAB, Bellaterra, 08193, SpainResume : Polymer semiconductors are attracting world wide interests as promising candidates forcost effective solar cells. They form soft solids characterised by strong intramolecular interactionsand weaker, Van-der-Waals type, intermolecular interactions. As a consequence, many polymerscan be processed from solution and at low temperatures yielding films with a variety ofnanostructures ranging from glassy to semicrystalline phases. In many cases, the structure of thefilm as deposited can be varied by soft thermal or vapour annealing, with the concomitant changein optical and electronic properties which determines the final performance of devices based uponthem. Here we present a novel technique to locally change the nanostructure of the as depositedfilms to produce layers with spatially separated regions of polymer chains with higherintermolecular interactions. The technique is based on printing a vapour of nitrogen mixed with thesolvent used to dissolve the organic material. We demonstrate the fabrication of waveguides usingvapour printing on polyfluorene films, where the solvent flux defines a thin stripe where thepolymer chains attain a planar conformation (aka beta phase) of higher refractive index whichconfines light within. We also show that this technique can be employed to fabricate positionsensitive detectors by fabricating gradients of crystallinity on polythiophene:fullerene mixtures.

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15:30 Coffee Break

Self-assembly and Nanostructures (Joint with Symposium G) : David Ginger

16:00 INVITED: Architecture vs. Function relationship in supramolecular nanomaterials for organicelectronicsAuthors : Paolo Samorí* ISIS-UdS & CNRS 7006 8 allée Gaspard Monge 67000 Strasbourg(France) E-mail: [email protected] Webpage : www.nanochemistry.frResume : Multifunctional materials are key in organic (opto)electronics. However, their practicaluse requires the optimization of the self-assembly of multimodular architectures at surfaces usingnon-conventional methods, their controlled manipulation and responsiveness to external stimuli,and the study of various physico-chemical properties at distinct length scales. I will review recentresults we obtained on: (i)Development of new (post)processing methods to produce highlyordered supramolecular electroactive architectures.[1] (ii)Supramolecular scaffolding to controlwith a sub-nm precision the position of functional units at surfaces.[2] (iii) Ordered responsiveinterfaces to realize light-powered mechano-chemical switches operating at surfaces and opticallyswitchable FETs.[3] (iv) SPMs beyond imaging to map by KPFM the photovoltaic activity in anorganic solar cell,[4] and to locally reduce graphene oxide with an AFM tip.[5] (v) Supramolecularapproaches to organic electronics to improve the performance of FETs, e.g. by tailoring ofpercolation parthways for charge transport in polycrystalline films.[6] References [1](a)Adv.Funct.Mater. 2007,17,3791. (b)PCCP 2010,12,4473 [2](a) Angew. Chem. Int. Ed.2007,46,245. (b) Adv. Mater. 2009,21,1131. (c)Adv. Mater. 2008,20,2433 [3](a)JACS2008,130,9192. (b)Angew. Chem. Int. Ed. 2008,47,3407 [4](a)Acc. Chem. Res. 2010,43, 541.(b)JACS 2008,130,780. (c)JACS 2008,130,14605 [5]JACS 2010,132,14130 [6]JACS 2009,131,7055

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16:30 Ordered semiconducting self-assembled monolayers on polymeric surfaces applied in organicintegrated circuitsAuthors : Fatemeh Gholamrezaie*, Simon G. J. Mathijssen, Edsger C. P. Smits, Tom. C.T. Geuns,Paul A. van Hal, Sergei A. Ponomarenko, Heinz-Georg Flesch, Roland Resel, Eugenio Cantatore,Paul W.M. Blom and Dago M. de LeeuwResume : In self-assembled monolayer electronics, the basic building block is the self-assembledmonolayer field-effect transistor (SAMFET), in which the semiconductor is a single molecular layerspontaneously formed on the gate dielectric. Recently the first SAMFETs on the SiO2 gate dielectricwere reported and combined into integrated circuits. Here we demonstrate that SAMFET on thepolymeric gate dielectric can be used to make organic integrated circuits. Two-dimensional highlyordered self-assembled monolayer directly grown on a bare polymer surface. By simplysubmerging the substrate into a solution containing the synthesized molecules, a densely packedmonolayer is self-assembled. The semiconducting molecules consist of a pi-conjugated coreseparated by a long aliphatic chain from a mono-functionalised anchor group. The driving force toform highly ordered SAMs is packing of the liquid crystalline molecules caused by the interactionsbetween the linear alkane moieties and the pi-pi stacking of the conjugated thiophene units.Grazing incidence X-ray diffraction shows the Bragg rods of the monolayer are well defined. Thesmall in-plane width of the rods is a clear evidence of high order and large crystalline 2D domainswithin the monolayer. In order to form a conducting path in between the source and drainelectrode, the molecules in the self-assembled monolayer (SAM) should be intimately connected.Any structural imperfection as voids or grain boundaries leads to potential barriers and, hence, toa deteriorated charge carrier mobility. The electrical connectivity between the molecules isinferred from electrical transport measurements. Semiconducting SAMs are utilized in field-effecttransistors and combined into integrated circuits as 4-bit code generators. The fully functionalcircuits demonstrate long-range order over large areas, which can be regarded as the start offlexible monolayer electronics.

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16:45 Control of size, shape, and alignment of single crystals of organic semiconductorsAuthors : Yves Henri Geerts* ([email protected]), Guillaume Schweicher, Gabin Gbabode, ClaireAmato, Nicolas Paquay, Université Libre de Bruxelles (ULB), Faculté des Sciences, Laboratoire deChimie des Polyméres, CP 206/1, Bd du Triomphe, 1050 Bruxelles, Belgique Roland Resel, MarkusKoini, Institute of Solid State Physics, Graz University of Technology, Petersgasse 16, A-8010 Graz,AustriaResume : Order is amongst the most important parameters that govern the physics of organicsemiconductors (OSCs) [1] However, materials must be ordered at all length-scales, frommolecular dimensions to macroscopic distances [2]. Liquid crystals constitute a unique class ofmaterials that spontaneously self-assembles into single domain thin films with specific alignment[3-5]. Patterning of aligned single domains of liquid crystalline OSCs has recently beendemonstrated [6,7]. Nevertheless, liquid crystalline semiconductors suffer from numerousstructural defects created by their partial liquid character and that limit their charge carriermobility [1,8,9]. Single crystals exhibits the highest charge carrier mobility of organic materialsbut their size, shape and alignment can not be controlled yet. Recently, we have demonstratedthat the size, shape and alignment of organic single crystals of OSCs can be modified with the useof a thermal gradient that allows the separation of nucleation and growth. We will report severalexamples of directional crystallization and discuss the physical parameters that allow thefabrication of single crystals. Information on our activities and publications are available at:http://www.ulb.ac.be/sciences/chimpoly. The work has been supported by the FP7-ONE-P projectunder grant agreement n° 212311, see http://www.one-p.eu/public. 1. S. Sergeyev … Y. H.Geerts, Chem. Soc. Rev. 2007, 1902 2. V. De Cupere … Y. H. Geerts, Langmuir 2006, 22, 7798 3.E. Pouzet …Y. H. Geerts, J. Phys. Chem. C, 2009, 113, 14398 4. G. Schweicher … Y. H. Geerts,Chem. Mater. 2009, 21, 5867 5. G. Zucchi, … Y. H. Geerts, R. Lazzaroni, J. Phys. Chem. B, 2009,113, 5448 6. M. Cavallini … Y. H. Geerts, F. Biscarini, Adv. Mater. 2009, 21, 4688 7. P.-O. Mouthuy… Y. H. Geerts, A. M. Jonas, Nano Lett. 2007, 7, 2627 8. V. Lemaur … Y. H. Geerts … B. Nysten, J.Phys. Chem. C, 2010, 114 9. Y. Olivier … Y.H. Geerts … J. Cornil, J. Phys. Chem. B 2009, 113,14102

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17:00 Self growing optics and electronics from organic nanofibersAuthors : Roana M. de Oliveira Hansen*, Jakob Kjelstrup-Hansen and Horst-Günter Rubahn MadsClausen Institute, University of Southern DenmarkResume : Light-emitting organic nanofibers made from organic molecules such aspara-hexaphenylene (p6P) molecules exhibit a wide range of useful optical properties [1] such asintense, anisotropic luminescence, waveguiding, and lasing. In order to fabricate new devices onthe basis of these nanofibers, they have to be combined with underlying device architecture. Here,we show how sophisticated growth control by an appropriately structured platform can lead to selfgrowing optic and electronic devices including nanostructures. The top down nano-structures aremade by electron-beam lithography on a silicon dioxide-coated silicon substrate followed by golddeposition and lift-off to form a field-effect transistor platform. The p6P molecules are thendeposited by vapour deposition. It is known that nanofibers from p6P molecules grow on goldsurfaces [2]. In the present case the underlying surface structures lead to the formation ofnanofibers bridging the gold structures that make up the source and drain electrodes. Electricalcharacterization shows that the nanofibers exhibit p-type properties, and the electrical propertiesdepend of the device platform design. 4-point electrical measurements show ohmic behavior, andelectroluminescence can be observed if an AC voltage is applied to the gate terminal. [1] F. Balzerand H.-G. Rubahn, Adv. Funct. Mater. 15, 17 (2005) [2] F. Balzer, L. Kankate, H. Niehus, R. Frese,C. Maibohm and H.-G. Rubahn, Nanotech. 17, 984 (2006)

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17:15 Organic-Organic Heteroepitaxy of Red-, Green-, and Blue-Emitting NanofibersAuthors : Clemens Simbrunner*(1), Francesco Quochi (2), Gerardo Hernandez-Sosa (1), MartinOehzelt (3), Roland Resel (4), Günter Hesser (5), Martin Arndt (5), Michele Saba (2), Andrea Mura(2), Giovanni Bongiovanni (2) and Helmut Sitter (1) (1) Institute of Semiconductor and Solid StatePhysics, Johannes Kepler University Linz, Austria (2) Dipartimento di Fisica, Universita di Cagliari,SLACS-INFM/CNR, I-09042 Monserrato (CA), Italy (3) Institute of Experimental Physics, JohannesKepler University Linz, Austria (4) Institute of Solid State Physics, Graz University of Technology,Austria (5) ZONA (Zentrum f. Oberflächen und Nanoanalytik), Johannes Kepler University Linz,AustriaResume : In recent years, heteroepitaxy of organic-organic nanostructures has beendemonstrated as a valuable technique to explore the full potential of organic semiconductors foroptoelectronic applications. Crystalline and highly ordered heterostructures with differentmorphology and molecular orientations can be realized by heteroepitaxy starting from conjugatedoligomers, aimed at tailoring their optical properties and transport characteristics [1-4].Para-hexaphenyl (p-6P) and sexithiophene (6T) are good model systems for heteroepitaxy as wellas important oligomers for device applications, and hence, several studies have been conducted onthe p-6P/6T material couple. Here we show by combining optical, structural, and morphologyinvestigations that organic-organic heteroepitaxy can be used to produce multilayered organicnanofibers with high crystallinity, well-defined epitaxial relationship along different materials’phases, sharp molecular azimuthal order, and long-range morphological homogeneity [5].Directed growth of sexithiophene on a para-sexiphenyl fiber template on muscovite mica results inhighly crystalline and oriented hetero-nanostructures with molecules laying parallel to thesubstrate, yielding strong optical polarization anisotropy in a broad band of wavelengths.Achievement of broad band optical waveguiding in blue, green, and red spectral regions couldenlarge the horizon of potential applications of epitaxial organic nanofibers. Organic nanofibersfeaturing optical waveguiding and random lasing could enable the realization of active photonicsensors with high sensitivity. Moving from single (blue) band operation of pure p-6P fibers to the

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triband operation based on heteroepitaxial p-6P/6T fibers would then allow for increasing sensingcapabilities and data volumes. [1] S. C. B. Mannsfeld, K. Leo, T. Fritz, Phys. Rev. Lett. 94, 056104(2005) [2] S. Timpanaro, A. Sassella, A. Borghesi; W. Porzio, P. Fontaine, M. Goldmann, Adv.Mater. 13, 127–130 (2001) [3] M. Oehzelt, G. Koller, J. Ivanco, S. Berkebile, T. Haber, R. Resel; F.P. Netzer, M. Ramsey, Adv. Mater. 18, 2466–2470 (2006) [4] G. Koller; S. Berkebile, J. R. Krenn, F.P. Netzer, M. Oehzelt, T. Haber, R. Resel, M. G. Ramsey, Nano Lett. 6, 1207–1212 (2006) [5] C.Simbrunner, F. Quochi, G. Hernandez-Sosa, M. Oehzelt, R. Resel, G. Hesser, M. Arndt, M. Saba, A.Mura, G. Bongiovanni and H. Sitter, ACS Nano, 4 (10), 6244–6250 (2010)

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Charge Transport and Microstructure I : Roland Resel

08:30 INVITED: Charge Transport in Supramolecular Assemblies: An Atomistic InsightAuthors : Jérôme Cornil*, Laboratory for Chemistry of Novel Materials, University of MonsResume : Charge transport plays a key role in defining the performance of most organic-baseddevices. Transport is typically described in two extreme cases, namely the band regime versusthe hopping regime. Many electronic effects in organic semiconductors tend to favor a hoppingpicture in devices at room temperature. In this regime, macroscopic models have beendeveloped over the years to characterize the influence of several parameters (such astemperature, electric field amplitude, disorder, charge carrier density) on the mobility values.Most of them have in common to involve effective parameters that do not take fully into accountthe nature and relative position of the interacting molecules. On the other hand, quantum-chemical calculations have been extensively used recently to calculate all parameters governingthe rate of charge transfer between two interacting molecules in the hopping regime, thus withan explicit account of the chemical structure and actual packing of the molecules. In this talk, wewill survey some of our recent studies aiming at the description of the various transportparameters in a large variety of systems. We will also illustrate that a bridge can be establishedbetween the molecular and macroscopic worlds by performing Monte-Carlo (MC) simulationsbased on the calculated transfer rates in order to evaluate charge mobility values within thehopping regime in supramolecular assemblies from calculated molecular parameters.

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09:00 Electric field and grain size dependence of Meyer-Neldel energy in organic filmsAuthors : Mujeeb Ullah*(1), A. Pivrikas (2), I. I. Fishchuk (3), A. Kadashchuk (4,5), P. Stadler(2), C. Simbrunner (1), N. S. Sariciftci (2) and H. Sitter (1) (1)-Institute of Semiconductor andSolid State Physics, Johannes Kepler University of Linz, A-4040 Linz, Austria (2)-Linz Institute ofOrganic Solar Cells, Johannes Kepler University of Linz, A-4040 Linz, Austria. (3)-Institute forNuclear Research, Natl. Academy of Sciences of Ukraine, Prospect Nauky 47, 03680 Kyiv, Ukraine(4)-IMEC, Kapeldreef 75, B-3001, Heverlee, Belgium. (5)-Institute of Physics, Natl. Academy ofSciences of Ukraine, Prospect Nauky 46, 03028 Kyiv, UkraineResume : We systematically studied Meyer-Neldel rule for charge carrier mobility measured inC_60-based organic field-effect transistors (OFETs) [1] at different applied source drain voltagesand at different morphologies of semiconducting fullerene films. A decrease in the Meyer-Neldelenergy E_MN from 36 meV to 32 meV was observed with changing electric field in the channel.Concomitantly a decrease from 34 meV to 21 meV was observed too by increasing the grain sizeand the crystallinity of the active C60 layer in the device. These empiric findings are inagreement with the hopping-transport model for the temperature dependent OFET mobility inorganic semiconductors with a Gaussian density of states (DOS) [2, 3]. Experimental resultsalong with theoretical descriptions are presented. 1. Mujeeb Ullah, T.B. Singh, H. Sitter, N.S.Sariciftci, Applied Physics A, Materials Science & Processing 97 (2009), 521. 2. Mujeeb Ullah, I. I.Fishchuk, A. Kadashchuk, P. Stadler, A. Pivrikas, C. Simbrunner, V. N. Poroshin, N. S. Sariciftci,and H. Sitter, Appl. Phy. Lett. 96,213306 (2010). 3. I. I. Fishchuk, A. K. Kadashchuk, J. Genoe,Mujeeb Ullah, H. Sitter, Th. B. Singh, N. S. Sariciftci, and H. Bässler, Phys. Rev. B 81, 045202(2010).

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09:15 Electrochemical doping of pentacene thin films: From spectroscopic structure characterization toapplicationsAuthors : P. Stadler* (1), B. Meana-Esteban (1,2,3), S. Schaur (1), H. Neugebauer (1) and N. S.Sariciftci (1) 1) Linz Institute for Organic Solar Cells (LIOS), Physical Chemistry, Johannes KeplerUniversity of Linz, A-4040 Linz, Austria 2) Laboratory of Materials Chemistry and ChemicalAnalysis, Department of Chemistry, University of Turku, FI-20014 Turku, Finland 3) TurkuUniversity Centre for Materials and Surfaces (MATSURF), University of Turku, FI-20014 Turku,FinlandResume : Pentacene has gained interest in organic electronics for its ambipolar properties. Inthis contribution, we show the characterization of the electronic structure of evaporatedpentacene thin films by means of spectro-electrochemistry. In addition, we apply electrochemicaldoping directly to an organic field-effect transistor (OFET) for decreasing the injection barrier ofholes. For the study of the electronic structure of charge carriers of both signs electrochemicaland in-situ spectroscopic techniques have been used. The p- and n-doping of pentacene ismeasured by voltammetric scans. The data show the HOMO and LUMO levels and the transportbandgap at 2.2eV. In the UV-VIS and IR distinct differences in the electronic structures betweenp- and n-doping are observed. The results are in agreement with theoretical considerations from

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density function theory calculations and empirical data of transistor characteristics, where animbalance in the carrier mobility is found. IR-absorption bands due to molecular vibrations ofn-doped pentacene were found at lower energies compared to the p-doped material. This isattributed to a higher localization of electrons compared to holes. The fact that pentacene can bereversible doped motivated us to implement the doping directly to an OFET. By electrochemicalp-doping pentacene in the vicinity of the contacts, the injection barrier for holes is decreased,which is reflected in an increase of the transistor’s on/off ratio after doping.

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09:30 Role of the film morphology on the ambipolar charge transport properties of a quinoidaloligothiophene derivativeAuthors : J.C. Ribierre*,1,2 T. Fujihara,2 S. Watanabe,3 M. Matsumoto,3 T. Muto,2 T. Takaishi,2A. Nakao,2 S. Matsumoto,4 S. Inoue,2 A. Muranaka,2 D. Hashizume,2 M. Uchiyama,2 T.Aoyama2 1 Ewha Womans University, Department of Physics, Korea 2 Advanced ScienceInstitute, RIKEN, Japan 3 Grad. Sch. Ind. Sci. Technol., Tokyo Univ. Sci., Japan 4 Grad. Sch. Env.Inf. Sci., Yokohama Nat. Univ., Japan Email: [email protected] : The use of ambipolar OFETs provides new alternative approaches in the fabrication oflogic circuits and can suppress the requirement of patterning p-type and n-type devices on thesame substrate. However, ambipolar OFETs often show moderate field-effect mobilities and highoff-currents, leading to organic logic circuits with high power consumption. In this context, thespatial and selective control of the ambipolar charge transport properties can greatly improve theperformance of the ambipolar organic integrated circuits. Here, we report on the reversiblemajority carrier type conversion in solution-processed OFETs based on the quinoidaloligothiophene derivative [QQT(CN)4]. As-prepared QQT(CN)4 OFETs present an ambipolarp-type dominant behavior. These devices can be converted to n-type by either thermal annealingor laser irradiation. In addition, quasi reversible conversion from n-type to ambipolar behaviorcan be achieved by a solvent vapor treatment. A combination of experimental techniquesincluding x-ray diffraction and UV photoelectron spectroscopy will be used to clarify themechanism of these conversions. The results will demonstrate the major role played by the filmmorphology on the charge transport properties of QQT(CN)4 thin films. This study provides a newapproach for the realization of CMOS logic circuits based on a monolithic solution-processableorganic semiconductor.

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09:45 Optically induced instabilities in P3HT field-effect transistorsAuthors : Lorenz Kehrer, Christian Melzer and Heinz von Seggern* Electronic MaterialsDepartment, Institute of Materials Science Technische Universität Darmstadt, Petersenstraße 23,64287 Darmstadt, GermanyResume : Towards application functional stability of organic electronic devices for all-day use isstill a great challenge. In the present talk we present an oxygen driven, light induced instabilityin poly (3-hexylthiophene) state-of-the-art field-effect transistors foreseen to work in organicRFID tags as a barcode replacement. Experimentally a substantial shift of the threshold-voltageand an increase in the off-current by 3 orders of magnitudes has been observed by illuminatingtop-gate poly(3-hexylthiophene) based field-effect transistors with visible light under forwardgate bias. The origin of this long lasting instability is attributed to optically filled electron trapsinduced by oxygen in the semiconductor shifting the threshold voltage and increasing the dopinglevel. The temporal evolutions of the optically induced changes in the OFET characteristics underdifferent thermal conditions will be highlighted. The discussed instability is crucial for logicelements where OFETs are hold in off-state, thus under depletion, thereby possibly affecting thefunctionality of the employed logic circuit.

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10:00 Coffee Break

Charge Transport and Microstructure II : Kilwon Cho

10:30 INVITED: How does disorder and microstructure affect transport in organic semiconductors?Authors : Alberto Salleo*, Jonathan Rivnay, Leslie Jimison, Rodrigo Noriega Materials Science andEngineering, Stanford University Michael F. Toney Stanford Synchrotron Radiation LightsourceAntonio Facchetti PolyeraResume : It is difficult to fundamentally understand transport in semiconducting polymers asthey are neither crystalline nor amorphous and their microstructure plays a central role ingoverning charge transport. We apply classical Materials Science concepts towards understandinghow organic semiconductors “work”. Using advanced synchrotron-based X-ray characterizationtechniques we are able to define and measure structural order at different length-scales as wellas degree of crystallinity. Understanding disorder is the key to determining charge transportmechanism. For instance, static cumulative disorder (e.g. paracrystallinity) –which we can nowmeasure quantitatively– provides a fundamental justification to using a mobility edge modelcausing a distribution of tail states in the gap. Furthermore, we are able to provide a structuralinterpretation of these trap states, which manifest themselves as a broad sub-threshold region intransistor characteristics. Finally, I will show an example of a polymer whose texture (edge-onvs. face-on) can be controlled by simple thermal anneal. The effect of texture on transport will beanalyzed as well.

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11:00 Correlating Charge Transport Performance to the Surface and Bulk Structure of a High-mobilityElectron Transporting PolymerAuthors : Torben Schuettfort* 1, Sven Huettner 1, Lars Thomsen 2, Samuele Lilliu 3, EmyrMacdonald 3 and Chris McNeill 1 1 Cavendish Laboratory, University of Cambridge, Cambridge,United Kingdom; 2 The Australian Synchrotron, 800 Blackburn Rd, Clayton, Victoria 3168

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(Australia); 3 School of Physics and Astronomy, Cardiff University, Cardiff, United Kingdom.Resume : In order to understand the origin of the high electron mobility in the novel conjugatedpolymer poly([N,N9-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,59-(2,29-bithiophene)), P(NDI2OD-T2), we present a range of structural, optical and electricalcharacterisations. Thermal treatment is used to produce films of different crystallinity asdetermined by Grazing-Incidence X-ray Diffraction (GIXD) and Atomic Force Microscopy (AFM),allowing comparison of as-cast, annealed and amorphous melt morphologies. The GIXDmeasurements confirm the extended in-plane lamellae ordering and out-of-plane π-π stackingwithin ordered regions. However, Near-Edge X-ray Absorption Fine Structure (NEXAFS)Spectroscopy, which is sensitive to all molecules in the film, indicates that the surface as well asthe bulk contains a significant amorphous content regardless of heat treatment. Opticalabsorption measurements show a blue shift of the charge-transfer absorption with heattreatment both for the annealed film with highest crystallinity and the amorphous melt. Thisreduction in electronic relaxation may be correlated to an observed reduction of electron mobilityin field effect devices where the active layer was subjected to prior heat treatment. Our resultsexpress a complicated interplay between film morphology, electronic structure and chargetransport and show that the relationship between crystallinity and charge mobility is notnecessarily straightforward.

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11:15 Deep Insight into the Spectroscopic Properties of a High Mobility n-type conjugated Polymer withImplications on Morphology and Charge TransportAuthors : Robert Steyrleuthner* (1), Marcel Schubert (1), Zhihua Chen (2), Antonio Facchetti (2)and Dieter Neher (1) (1) Institut für Physik und Astronomie, Universität Potsdam, Germany (2)Polyera Corporation, USAResume : Electrical properties of conjugated polymers are severely influenced by themorphology of the semiconducting layer. Recently, Facchetti and coworkers reported a noveln-type polymer (Polyera ActivInk N2200) with an exceptionally high electron field-effect-mobilityof up to 0.85 cm²/Vs [1]. We could already show that the bulk mobility in this material is indeedhigh, though electron injection is contact limited for all used low work function cathodes. Weproposed these barriers become present in combination with a high electron mobility material[2]. While it was initially believed that layers from N2200 are amorphous, x-ray studies byRivnay et al. on N2200 showed an exceptional in-plane order with distinct “pi-stacking” of thenaphthalene diimide cores [3]. The purpose of our work was to study the morphology of N2200layers prepared from different solvents and annealed at different temperatures. Information onthe chain packing and layer structure was obtained by performing UV-Vis absorbance,photoluminescence, AFM and SNOM measurements on thin films and solutions. We could identifydistinct absorbing species and assign them to intrachain charge-transfer excitons in theamorphous phase and to interchain excitations on aggregated chains. On this basis, conclusionsregarding the morphology of the semicrystalline films are drawn and related to bulk chargetransport properties. [1] H. Yan, Z. H. Chen, Y. Zheng, C. Newman, J. R. Quinn, F. Dotz, M.Kastler, and A. Facchetti, Nature 457, 679-U1 (2009). [2] R. Steyrleuthner, M. Schubert, F. Jaiser,J. C. Blakesley, Z. Chen, A. Facchetti, D. Neher, Advanced Materials, 22, 2799 (2010). [3] J.Rivnay, M. F. Toney, Y. Zheng, I. V. Kauvar, Z. Chen, V. Wagner, A. Facchetti, A. Salleo, AdvancedMaterials, 22, 4359 (2010).

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11:30 Charge injection and transport in a high-mobility n-type polymer semiconductorAuthors : M. Caironi* (1,2), D. Fazzi (2), Z. Chen (3), A. Facchetti (3), D. Natali (2,4), and H.Sirringhaus (1) 1 Cavendish Laboratory, J. J. Thomson Avenue, Cambridge CB3 0HE, UnitedKingdom 2 Italian Institute of Technology, Center for Nano Science and Technology,CNST-IIT@PoliMi, Via Pascoli 70/3, 20133 Milano, Italy 3 Polyera Corporation, 8045 LamonAvenue, Skokie, Illinois 60077, USA 4 Politecnico di Milano, D.E.I., Piazza L. da Vinci 32, 20133Milano, ItalyResume : Recently,high mobility OFETs based on P(NDI2OD-T2) were demonstrated.Previousinvestigations revealed the presence of ordered domains with a predominantly out-of-planepi-stacking orientation,challenging the notion that face-on orientations are not suitable for highmobility OFETs.Another intriguing aspect is represented by the efficient electron injection fromhigh work function metals.Here we contribute to the understanding of both aspects by reportingour findings in staggered P(NDI2OD-T2) FETs. First we address electrons injection,reporting onthe detailed characterization of the contact resistance (RC).Despite the presence of an energeticbarrier at the injecting contact, Au electrodes show a surprisingly low RC,dependent on thelateral field and dominated by the source component.Then we report on electron transportinvestigations based on variable-temperature electrical measurements,charge modulationspectroscopy and quantum chemical calculations.Our results point to an unusually uniformenergetic landscape of sites for charge carrier transport,which is believed to be the main reasonfor the observed high mobility.We suggest that the reorganization energy plays an important rolein determining the activation energy for the mobility, consistently with a lateral field-independenttransport at temperatures down to 10 K and quantum chemical calculations that show an efficientelectronic coupling between adjacent units and a reorganization energy of a few hundreds ofmeV.

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11:45 Optical spectroscopy of charge transfer doping and electron trapping in polymer semiconductordevicesAuthors : Riccardo Di Pietro*(1), Michael C. Gwinner(1), Yana Vaynzof(1), Kathryn J.Greenberg(1), Enrico Gili(1), Antonio Facchetti(2) and Henning Sirringhaus(1) (1) - Departmentof Physics, Cavendish Laboratory J. J. Thomson Avenue, Cambridge CB3 0HE (UK) (2) - Polyera

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Corporation, 8045 Lamon Avenue Skokie, IL 60077 (USA)Resume : We have developed a high sensitivity optical spectroscopy technique that allowsmonitoring subtle changes of the optical absorption of an organic device at a sensitivity level of <1 part in 1000 as a function of time. This technique allows in-situ spectroscopic investigation ofsome of the key electronic processes in fully functional device structures. The technique has beensuccessfully applied to study the mechanism of charge transfer doping of conjugated polymerfilms by MoO3, quantify doping efficiency and investigate the doping efficiency under differentatmospheric conditions. We have also used the technique to investigate the mechanism for biasstress degradation in n-type organic FETs of poly{[N,N9-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,59-(2,29-bithiophene) (P(NDI2OD-T2). By detecting subtlechanges in the optical transmission spectrum during the bias stress that reflect differences in thespectroscopic signature of mobile and trapped electrons it is possible to investigatespectroscopically mechanisms for electron trapping in such devices. The fundamental role ofatmospheric contaminants in the stressing mechanisms is determined by comparing stress effectsin vacuum and in air, and the results are analysed in view of possible electrochemical reactionshappening at the interface with the dielectric, and how this affects the electrical characteristics ofthe device.

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12:00 INVITED: Ordering in Semiconducting Polymers for Thin Film TransistorsAuthors : Michael L. Chabinyc Materials Department University of California Santa BarbaraResume : Molecular interfaces are intrinsic features of organic electronic devices particularly inthin film transistors (TFTs) where charge accumulates in the first few molecular layers near thegate dielectric. There have been significant advances in development of high performancesemiconducting polymers, but less is understood about the design of dielectric polymers and theirimpact on charge transport. We will describe recent efforts using dry transfer methods to formcontrolled interfaces in polymer TFTs that allow us to begin to disaggregate the contribution ofmicrostructure, dielectric constant, and molecular structure to the observed field-effect mobilityof the semiconducting polymer. The microstructure of semicrystalline semiconducting polymerstransferred to a variety of dielectric polymers has been characterized by both hard and soft x-rayscattering, atomic force microscopy and other techniques. We find that the interfacialmicrostructure is the dominant factor affecting field effect mobility rather than simplecharacteristics such as the dielectric constant.

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12:30 Lunch

Synthesis and New Materials : Michael Chabinyc

14:00 INVITED: Towards high mobility ambipolar polymersAuthors : Martin Heeney* Dept. Chemistry, Imperial College London, UKResume : Ambipolar organic FETs that are capable of both hole and electron transport underappropriate biasing conditions are an interesting approach to CMOS type logic. CMOS has manypotential advantages over unipolar logic including lower power consumption, improvedrobustness and faster switching speeds. Polymer materials that are capable of balanced, highmobility hole and electron transport from common source/drain electrodes are thus highlydesirable. In this talk I will discuss strategies towards the design of balanced, high mobilityambipolar polymers. I will discuss approaches to facilitate hole and electron transport bymodification of the polymer structure. The effects of these changes in molecular structure on thinfilm morphology, electronic energy levels and ambipolar transistor performance will be discussed.

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14:30 Small molecular weight n-type organic semiconductor having phthalimide moietiesAuthors : Ken-ichi Nakayama*, Yohei Hashimoto, Kenta Shingu, Yong-Jin Pu, Junji Kido YamagataUniversity, JST-PRESTO, JapanResume : Organic field-effect transistors (OFETs) have attracted much attention, and varioustypes of organic semiconductor materials have been reported. However, only a few types ofsoluble n-type organic semiconductor molecules exist, and their performance is generally worsethan that of p-type materials. There are two design guidelines to achieve high performance inn-type molecules; one is large fused-ring system to enhance crystallinity in the film, and anotheris electron withdrawing substituent to make the LUMO level lower. However, these strategiesusually make the molecules insoluble. In this study, we designed small molecules that aresuitable for wet-processed n-type OFETs. We employed phthalimide moiety to obtain n-typecharacter, and non-fused π-system to increase solubility. Three compounds of 1,4-bis(N,N’-octyldiphthalimide) derivatives were synthesized. Each compound has core moiety of bithiophene(DPIBT), benzene (DPIBen), and terephthalonitrile (DPITN), respectively. We evaluated OFETperformance of these compounds using vacuum-evaporated films using in top contactconfiguration device. All the three compounds showed n-type operation; in particular, DPIBTshowed electron mobility around 0.25 cm2/Vs when the substrate temperature was elevated. Wealso fabricated wet-processed OFET from chloroform solution, and DPIBT showed electronmobility of 0.036 cm2/Vs.

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14:45 Unraveling the Effects of Additional Thiophene Units on Charge Transport in Poly(fluorene-thienyl-benzothiadiazole) PolymerAuthors : Zhuoying Chen* 1,4, Junfeng Fang 2, Feng Gao 1, Thomas J. K. Brenner 1, Kulbinder K.Banger 1, Xingzhu Wang 2, Wilhelm T. S. Huck 2,3, Henning Sirringhaus 1 (1) CavendishLaboratory, Department of Physics, University of Cambridge, CB3 0HE, United Kingdom (2)Melville Laboratory for Polymer Synthesis, Department of Chemistry, University of Cambridge,CB2 1EW, United Kingdom (3) Radboud University Nijmegen, Institute for Molecules and

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Materials, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands (4) Present Affiliation:Institut Matériaux Microélectronique Nanosciences de Provence (IM2NP), UMR CNRS 6242,Service 231, Avenue Escadrille Normandie Niemen, 13397 Marseille Cedex 20, FranceResume : We report a comparative study of optical properties, structure and morphology, field-effect transistor (FET) and solar cell performance between two donor-acceptor polyfluorenecopolymers, poly(4-(3,4'-dihexyl-2,2'-bithiophen-5-yl)-7-(5'-(9,9-dioctyl-9H-fluoren-2-yl)-3,4'-dihexyl-2,2'-bithiophen-5-yl)benzo[c][1,2,5]thiadiazole) (F8TTBTT), and its predecessorpoly((9,9-dioctylfluorene)-2,7-diyl-alt-[4,7-bis(3-hexylthien-5-yl)-2,1,3-benzothiadiazole]-2',2"-diyl) (F8TBT). Compared to F8TBT, F8TTBTT has two more thiophenemoieties incorporated in its monomer structure. By presenting a complete characterization ofthese two polymers, we strive to understand the microscopic origin of the enhanced chargetransport associated with the addition of thiophene units. Our results point out that, withadditional thiophene units and a reduced band gap, F8TTBTT-based-FETs exhibit improved chargeinjection and significantly enhanced ambipolar field-effect mobilities reaching 5 × 10-2 cm2 V-1s-1 for holes and 4 × 10-3 cm2 V-1 s-1 for electrons. Supported by our results from Ramanspectroscopy, the enhanced carrier mobilities in F8TTBTT are most likely a result of an increasedbackbone planarization and interchain interaction. Ambipolar F8TTBTT FETs exhibit deep-red lightemission from within the transistor channel. Even though not fully optimized, F8TTBTT:PCBM solarcells were demonstrated to show comparable performance to F8TBT:PCBM devices.

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15:00 Poly(9,9-Dioctylfluorene) (F8) Based Conjugated Polyelectrolyte (CPE): Extended π ElectronConjugation Induced by Complexation with a Surfactant ZwitterionAuthors : Giuseppina Pace* (1,2), Guoli Tu (3,4), Emiliano Fratini (2), Sylvain Massip (1), WilhelmT. S. Huck (3), Piero Baglioni (2), Richard H. Friend (1) 1 Cavendish Laboratory, JJ ThomsonAvenue, Cambridge, CB3 0HE, United Kingdom [email protected] 2 Department of Chemistryand CSGI, University of Florence, 50019 Sesto Fiorentino (Firenze), Italy 3 Melville Laboratory forPolymer Synthesis, Department of Chemistry, University of Cambridge, CB2 1EW, UnitedKingdom 4 Wuhan National Laboratory for Optoelectronics, Huazhong University of Science andTechnology , Wuhan, 430074, ChinaResume : Over the past two decades semiconducting polymers have been proved to beimportant for use in optoelectronics applications.[1, 2] Among polymers, conjugatedpolyelectrolytes (CPEs) combine the semiconducting properties of the conjugated backbone withthe physical chemistry, in terms of solubility, self-assembly and reactivity, of polyelectrolytes.New polymer morphologies can be explored due to CPEs amphiphilicity and capability toelectrostatically interact with oppositely charged chemical species. Here we describe therelationship between morphological features and optical properties of newly synthesizedpoly(9,9-dioctylfluorene) (F8) based conjugated polyelectrolytes. We could achieve full controlover the self-assembly through the formation of CPEs complexes with surfactant zwitterions(ZW). Atomic Force Microscopy and Small Angle X-ray Scattering data show that theCPE-zwitterion complex is amphiphilic in nature, self-assembling into multi-lamellar structuresextended over many microns on a solid substrate. Importantly, the luminescence efficiency, lowin the uncomplexed polymer, is strongly increased as the complex is formed. We also showedthat the CPE-ZW complex is a more efficient injection layer in Polymer Light Emitting Diodes(PLEDs) than the pure CPE. This work represents a new approach in the use of CPEs inoptoelectronic applications trough their chemical and morphological modification. 1- Nature 1990,347, 539 2- Advanced Materials 2005, 17, 2411

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15:15 Biocompatible and Biodegradable Materials for Organic Field Effect Transistors and Circuits: Routetowards Green ElectronicsAuthors : Mihai Irimia-Vladu* 1,5, Pavel A. Troshin2, Melanie Reisinger1, Günther Schwabegger3,Reinhard Schwödiauer1, Yasin Kanbur4, Vladimir Razumov2, Helmut Sitter3, Siegfried Bauer1and Niyazi Serdar Sariciftci5 INSTITUTIONS: 1Department of Soft Matter Physics, JohannesKepler University, A-4040 Linz, Austria 2Institute of Problems of Chemical Physics of RussianAcademy of Sciences, Semenov Prospect 1, Chernogolovka, Moscow region, 142432, Russia3Institute of Semiconductor and Solid State Physics, Johannes Kepler University, A-4040 LinzAustria 4Middle East Technical University, Ankara, Turkey 5Linz Institute for Organic Solar Cells(LIOS), Department of Physical Chemistry Johannes Kepler University A-4040 Linz AustriaResume : Organic electronics has the potential to develop electronic products that arebiocompatible, bioresorbable, biodegradable or even capable to bio-metabolize. An ideal solutionfor the production of such devices involves the fabrication of the electronics either from naturalmaterials, or from materials that have been proved to be at least biocompatible. Here we reportthe combination of biocompatible and biodegradable substrates based on hard gelatine capsule,Shellac (wood finishing) or commercially available plastic foil based on starch, corn and polylacticacid (Ecoflex®, BASF) with fully natural or materials found in common commodity products, asgate dielectrics and organic semiconductors in low operating voltage organic field effecttransistors (OFETs). In a first example, low operating voltage OFETs are built on commerciallyavailable biodegradable plastic foil (Ecoflex®, BASF), comprising naturally occurring dielectrics:adenine, guanine, cytosine, thymine and widely accepted perylene diimide-a simple red dye usedextensively in cosmetic industry. In a second example, complete bio-materials based OFETs areintroduced based on glucose, lactose, sucrose, for the gate dielectrics with vacuum processedindigo or solution processed beta-carotene as organic semiconductors respectively. In a thirdexample, fully degradable devices are produced on hard gelatine capsule substrates comprisinglayers of adenine and guanine for organic dielectrics and indanthrene yellow G and indanthrenebrilliant orange RF (two vat dyes used extensively in textile industry) for the organicsemiconductor. Tremendous improvement of the OFETs characteristics are feasible simply byemploying aurin, a naturally occurring red-orange pigment as a smoothening layer for Ecoflex

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and hard gelatine capsule substrates or by employing the anodization of the aluminium gateelectrodes in combination with organic dielectric layers for the samples built on glass substrates.Examples of natural encapsulates for the fabricated devices are also presented, together withfully natural electronic circuits (inverters and memory elements) operating at low voltages. Suchtransistors may be seen at the heart of organic electronic circuits, to be used in low-cost, largevolume disposable or throwaway applications, such as food packaging, plastic bags, disposabledishware etc. There is also significant potential to use such electronic items in biomedicalimplants. The work was financially funded by Austrian Science Foundation “FWF” within theNational Research Network NFN on Organic Devices (P20772-N20, S09712-N08, S09706-N08 andS9711-N08) as well as by Russian Foundation for Basic Research (07-04-01742-а) and RussianMinistry of Science and Education (02-513-11-3382).

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15:30 Modulation of the Material Properties of Thin Polymer Films by Means of UV-lightAuthors : T. Griesser* (a), M. Edler (a), S. V. Radl (a), N. Muhr (a), W. Kern (a), G. Trimmel (b),A. Pavitschitz (c), Q. Shen (c), C. Teichert (c), H.-G. Flesch (d), M. Marchl (d), E. Zojer (d), R.Resel (d), G. Hernandéz Sosa (e), C. Simbrunner (e), H. Sitter (e), A. M. Track (d,f), G. Koller(f), M. G. Ramsey (f). (a) Institute of Chemistry of Polymeric Materials, University of Leoben,A-8700 Leoben. (b) Institute for Chemistry and Technology of Materials, Graz University ofTechnology, A-8010 Graz . (c) Institute of Physics, University of Leoben, A-8700 Leoben. (d)Institute of Solid State Physics, Graz University of Technology, A-8010 Graz (e) Institute ofSemiconductor and Solid State Physics, University of Linz, A-4040 Linz (f) Institute for Physics,Graz University, Universitätsplatz 5, A-8010 GrazResume : The tuning of material properties such as surface energy, surface reactivity, refractiveindex and electric conductivity in thin polymer films is crucial for modern organic electronic andoptical devices. In this study we report on photoreactive polymer films that offer the possibility ofa patterned modulation of these properties by means of UV-light.The investigated photoreactionsundergo either an isomerisation reaction or a photo cleavage reaction which results in polar andchemically reactive products.These photoproducts increase the surface polarity and surfacereactivity in the investigated polymer layers. The photo generated reactive groups can also beused for selective post exposure derivatization reactions in which functional molecule, e.g.fluorescent dyes, metal complexes and nanoparticles can be immobilized. In combination withlithographic techniques, functional surface patterns with micrometer resolution were obtained. Inaddition the photo isomerisation reactions lead to a large increase in the refractive index uponirradiation as shown by spectroscopic ellipsometry. Such index structures are useful to set upoptical waveguides and for optical data storage devices. Furthermore, we have investigated aphotosensitive conductive polymer whereas an illumination with UV light causes an increase inthe electric conductivity which was shown by CAFM-measurements. This polymeric material canbe used as electrodes in organic electronic devices such as OTFTs and OLEDs.

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15:45 Photoswitchable gate insulator in OFETsAuthors : Petro Lutsyk*, Krzysztof Janus, Juliusz Sworakowski, Institute of Physical andTheoretical Chemistry, Wrocław University of Technology, Wyb. S. Wyspianskiego 27, 50-370Wrocław, Poland; Gianluca Generali, Raffaella Capelli, Michele Muccini, Institute forNanostructured Materials (ISMN), CNR Division in Bologna, via P. Gobetti 101, I-40129 Bologna,Italy; Anna Kochalska, Stanislav Nešpůrek, Institute of Macromolecular Chemistry, Academy ofSciences of the Czech Republic, namesti Heyrovskeho 2, 162-06 Prague 6, The Czech Republic;*Corresponding author. Permanent address: Institute of Physics, National Academy of Sciences ofUkraine, Kyiv, Ukraine. (e-mail) [email protected] : Increasing interest in multistable photochromic systems observed in recent years hasbeen due to emerging applications in organic electronics and photonics [1]. There are manyexamples of using photochromic materials as admixtures to organic semiconductors in electronicdevices [2]. In the present communication we describe an organic field effect transistor (OFET) inwhich photochromic spiropyran was admixed to the gate insulator (PMMA) and not tosemiconductor (in this study we used n-type perylene derivative P13). The modulation of thesource-drain currents measured in studied OFETs was due to reversible photochemical reaction ofspiropyran, the photoswitching ratio depending on gate voltage. The phenomenon was attributedto changes in dipole moment of photochromic molecules during the reaction, its mechanism beingrelated to a contribution of the photochromic dipoles on the semiconductor-insulator interface andin the bulk of the insulator [3]. Acknowledgements This work was supported by the EuropeanCommission through the Human Potential Programme (Marie-Curie RTN BIMORE, Grant No.MRTN-CT-2006-035859) and, in part, by the Wroclaw University of Technology. [1] B.L. Feringa(Ed.), “Molecular Switches” Wiley-VCH, Weinheim 2001. [2] P. Lutsyk, J. Sworakowski, K. Janus,S. Nešpůrek, A. Kochalska, Mol. Cryst. Liq. Cryst. 522, 211 (2010). [3] P. Lutsyk, K. Janus, J.Sworakowski, G. Generali, R. Capelli, M. Muccini, J. Phys. Chem. C accepted (2011).

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16:00 Coffee Break

Poster Session I : Martin Brinkmann and Roland Resel

16:30 Charge transport properties of blends of conjugated polymers and organic small moleculesAuthors : A. Intaniwet*, C.A. Mills, M. Shkunov, P.J. Sellin and J.L. Keddie Department of Physics,University of Surrey, Guildford, Surrey GU2 7XH, UK *Corresponding author:[email protected] : Small molecule organic semiconductors, such as 6,13-bis(triisopropylsilylethynyl)(TIPS) pentacene, are known to have good charge transport properties due to their ability toform a well-organised polycrystalline structure [1]. However, a difficulty in the solutionprocessing of pure TIPS-pentacene because of the anisotropy of crystal formation [2] prevents it

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from being used for the production of large-area devices. To avoid this difficulty, in this research,TIPS-pentacene was blended with an amorphous polymer (poly(triarylamine) or (PTAA)) toimprove the processability. Under a polarized optical microscope, the blend shows a needle-likecrystal structure with its long axis parallel to the film surface, and the crystal size increases withan increasing amount of TIPS-pentacene. Analysis of the Si distribution in the blend film usingenergy dispersive X-ray analysis in a mapping mode has revealed that crystals are uniformlydistributed throughout the depth of the film. Data from a time-of-flight photocurrentmeasurement show a direct correlation between the charge-carrier (holes) mobility and theTIPS-pentacene concentration, leading to a mobility increase by up to a factor of 50. Blends ofPTAA and TIPS-pentacene were used as the active material in a diode structure within X-raydetectors [3]. The device using the PTAA blended with TIPS-pentacene demonstrated a sensitivitythat is higher than in a pure PTAA device by a factor four, because of the faster charge transportin TIPS-pentacene. [1] R. Hamilton, et al. Adv. Mater. 21, 1166 (2009). [2] R. L. Headrick, et al.Appl. Phys. Lett. 92, 063302 (2008). [3] A. Intaniwet, et al. ACS Appl. Mater. Interfaces. 2, 1692(2010).

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16:30 Preparation and characteristics of a microlens array for a digital holography application by aninkjet printing methodAuthors : Yong Suk Yang, In-Kyu You, and Jae Bon Koo Electronics and TelecommunicationsResearch InstituteResume : Recently single microlens and microlens arrays have played a fundamental role in anactual photonic technology. Numerous materials and a variety of processes, such as a se-lectiveelectrowetting and an imprinting, have been investigated for fabricating microlens arrays.Especially great interest has been concentrated on microlenses made with a simple fabricatingmethod. In this study, microlens array for a digital holography application was fabricated by aninkjet printing method. We studied the surface morphology and optical property of opticalmicrolens array fabricated by using piezoelectric microchannel mounted nozzles to depositpolymer droplets to various substrates via drop-on-demand (DOD) fashion. The surface ofsubstrates was modified chemically to get a hydrophobic property and the physical properties ofmicrolens array were investigated.

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16:30 The Top-Gate Organic Field-Effect Transistors based on poly(2,5bis(3-alkythiophen-2-yl)-thieno[3,2-b]thiophene) semiconducting polymerAuthors : Jinhua Li, Helen L. W. Chan and Feng Yan Department of Applied Physics, the HongKong Polytechnic University, Hung Hom, Kowlong, Hong Kong, ChinaResume : The liquid-crystalline conjugated polymer poly(2,5bis(3-alkythiophen-2-yl)-thieno[3,2-b]thiophene)(BTTTT) currently shows very high hole mobility of beyond 1cm2/Vs, indicating greatpromise for practical applications. However, such high mobility above 1cm2/Vs only can beobtained on SiO2 substrate with the surface modification of octyltrichlorosilane(OTS) in thebottom-gate geometry of organic field-effect transistors(OFETs). In this work, we fabricatedbottom contact top-gate (BCTG) OFETs by using PBTTT and different gate dielectrics, includingPolystyrene(PS) polymer, Poly(methyl methacrylate) (PMMA) polymer, and a high-k dielectricmaterial. For the devices with PS and PMMA gate insulator, we obtained hole mobilities of0.1cm2/Vs and 0.16cm2/Vs, respectively, and on/ off ratio up to 106. More importantly, thePBTTT OFETs with the high-k gate dielectric showed the mobility of 1.5cm2/Vs and the on/off ratioof about 105. We extracted the hole mobility and carrier densities relationship from the deviceperformance and found that the mobility increased with the increase of carrier density. Thereforethe high hole mobility observed in the OFETs with the high-k dielectric can be attributed to thehigh carrier density that can be achieved in the devices.

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16:30 Electronic structures of fullerene/calcium interface for n-type organic semiconducting devicesAuthors : Yeonjin Yi (Division of Industrial Metrology, Korea Research Institute of Standards andScience), Han-Ki Kim (Department of Advanced Materials Engineering for Information andElectronics, Kyung Hee University), Seong Jun Kang* (Department of Advanced MaterialsEngineering for Information and Electronics, Kyung Hee University)Resume : Interfacial electronic structure of fullerene deposited on calcium was investigatedusing in-situ ultraviolet photoelectron spectroscopy. The energy level alignment at the interfacewas estimated by combining both shifts of the highest occupied molecular orbital (HOMO) leveland the vacuum level during the step-by-step deposition of fullerene on calcium. The HOMO levelof fullerene shows shifts relating to band-bending, resulting in an electron injection barrier of 0.2eV with accumulation contact with the calcium substrate. The vacuum level reveals an interfacedipole with negative poles on the fullerene side. A gap states are formed at the interface region,which might pin the Fermi level and be responsible for the formation of the interface dipole. Weobtained a complete interfacial energy level diagram of fullerene/calcium.

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16:30 Work function loweirng of multilayer graphene transparent conducting filmsAuthors : Seong Jun Kang* (Department of Advanced Materials Engineering for Information andElectronics, Kyung Hee University), Yeonjin Yi (Division of Industrial Metrology, Korea ResearchInstitute of Standards and Science)Resume : A simple method to control the effective work function of graphene conductive films,which were synthesized by chemical vapor deposition (CVD) and transferred to dielectricsubstrates, were developed. The work functions of the graphene during the step-by-stepdeposition of aluminum were measured using in-situ ultraviolet photoelectron spectroscopy.Core-level spectra were also collected to investigate the chemical reaction when a small amountof aluminum was deposited on a graphene in a stepwise manner. The measurements revealed

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that the effective work function of graphene conductive films could be controlled from 3.77 to4.40 eV by a deposition of aluminum less than 0.6 nm thick on the graphene surface.

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16:30 Low temperature process of Inkjet-printed ZnO thin film transistorAuthors : Sang Chul Lim1, Seong Youl Kang1, Ji Young Oh1, Seong deok Ahn1, Hee-Ok Kim1, andKyoung Ik Cho1 1IT Convergence and Components & Materials Research Laboratory, Electronicsand Telecommunications Research Institute 138, Gajeongno, Yuseong-gu, Daejeon 305-700,KoreaResume : On the way towards wide-spread flexible large-area electronics, several features areof particular interest. With focus on low-cost applications, the manufacturing requires highthroughput, preferably realized by simple methods on large-area flexible substrates, for examplespin coating, inkjet-printing or roll-to-roll techniques. For solution processed ZnO field-effecttransistor (FET) devices, the highest electron mobility values are currently 1.65 cm2/Vs, howeverobtainable only after annealing at temperatures >300 ℃. Here we report our investigation on theformation, characterization, room temperature processing and inkjet printing behavior of amolecular precursor and adherence of such films in an FET device. ZnO nanoparticles weresynthesized using a facile sonochemical method with modification of previously conditions. TheZnO active channel layer was patterned with drops using a piezo ink-jet device. A single piezo-dispenser with a 50 µm orifice was used for ink-jet printing. The appropriate active channelregion was successfully formed on the substrate at a resolution of 200 dpi and a head frequencyof 300 Hz. For film synthesis, inkjet printed ZnO was annealed at 150 oC for 30 min in air. TheTFTs device has a channel width (W) of 100 µm and a channel length (L) of 10 µm. The IDS-VDScurves showed well-defined transistor characteristics with saturation effects at VG>-10 V andVDS>-20 V for the inkjet printing ZnO device. The carrier charge mobility was determined to be0.162 cm2 V-1s-1 with FET threshold voltage of -4 V and on/off current ratio 104

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16:30 Reduction of operational voltage in high mobility C60 based Organic Field Effect TransistorsAuthors : G. Schwabegger (1), Mujeeb Ullah (1), M. Irimia-Vladu (2), M. Reisinger (2), Y. Kanbur(3), P. Stadler (4), S. Bauer (2), N. S. Sariciftci (4), H.Sitter (1) (1) Institute of Semiconductorand Solid State Physics, Johannes Kepler University Linz, Austria (2) Institute of Soft MatterPhysics (SOMAP), Johannes Kepler University Linz, Austria (3) Department of Polymer Scienceand Technology, Middle East Technical University, Ankara, Turkey (4) Linz Institute of OrganicSolar Cells (LIOS), Johannes Kepler University Linz, AustriaResume : We report on the reduction of operational voltages of C60 based Organic Field EffectTransistors (OFETs). This was achieved by increasing the geometric capacitance of the dielectriclayers. One approach followed in our investigations was the application of Parylene-C as aninsulating layer. The polymeric Parylene films were prepared by vacuum deposition with a layerthickness of 225nm, which resulted in a reduction of the applied gate- and source-drain-voltagesby a factor of 10 as compared to previous works in our group utilizing a 2µm BCB film as adielectric layer[1]. Secondly metal-oxide/organic bilayers were prepared to combine the highdielectric constant of aluminum oxide (Alox) with the interface properties of organic layers (BCB,Polyethylene and Adenine). Alox was prepared by anodization of vacuum deposited Al films. Thislow temperature solution processing technique is capable of preparation of electrically dense filmswith thicknesses as low as 50nm. The measurements of the prepared OFETs show, that devicesare operating at gate voltages below 500mV, which is another factor of ten less as compared tothe Parylene devices. The output characteristics exhibit well saturated behavior and the transfercharacteristics shows on/off ratios >10³ as well as low hysteresis. The field effect mobilities ofthese devices are in the range of 2-5cm²/Vs for different passivation layers. [1] M. Ullah, T. B.Singh, H. Sitter, and N. S. Sariciftci, Appl. Phys. A: Mater. Sci. Process. 97, 521 (2009)

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16:30 Stabilization of organic thin film transistors behaviour via ion-implantationAuthors : B.Fraboni1, P.Cosseddu2, Y.Q. Wang3, R.K. Schulze3, Z.F. Di3, A.Cavallini1, M. Nastasi3and A.Bonfiglio2 1Dipartimento di Fisica, Università di Bologna, viale Berti Pichat 6/2, 40127Bologna, Italy 2Dipartimento di Ingegneria Elettrica ed Elettronica, Università di Cagliari, piazzad’Armi, 09123 Cagliari, Italy and CNR-INFM S3 via Campi 213/a 41100 Modena 3Los AlamosNational Laboratory MS-K771 Los Alamos NM 87545 USAResume : One of the open issues in organic electronics is the long-term stability of devices basedon organic materials, as oxidation is believed to be a major reason for early device failure. Thefocus of our research is to investigate the effects of low energy ion implantation in the reductionand control of the degradation of organic devices due to the exposure to atmosphere (i.e. oxygenand water). We have studied the effects of N and Ne irradiation on pentacene organic thin filmtransistors (OTFTs). Ion implantation induces strong molecular structure modifications that affectthe organic active layer, but we have observed that a controlled damage depth distributionpreserves the functionality of the device and its major transport parameters, i.e. carrier mobilityand threshold voltage. The electrical properties of the pentacene layer and of the OTFT have beeninvestigated by means of current-voltage and photocurrent spectroscopy analyses. We havecharacterized the structural modification induced by ion implantation and we have monitored theeffectiveness of this process in stabilizing the device carrier mobility and threshold voltage over along time (over 2000 hours), proving how ion implantation can be safely carried out on fullyoperational OTFTs. In particular, we have assessed by depth resolved XPS analyses that, byselectively implanting with ions that can react with the hydrocarbon matrix (e.g. N+), it ispossible to locally modify the charge distribution within the organic layer.

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16:30 Novel fluoropolymer gate dielectrics for organic transistor applicationsAuthors : Florian Colléaux, Jeremy Smith, Donal D.C. Bradley, and Thomas D. AnthopoulosDepartment of Physics and Centre for Plastic Electronics Imperial College London, BlackettLaboratory London SW7 2BW (UK)Resume : The role of the gate dielectric in high performance organic field-effect transistors(OFETs) is as important as the semiconductor itself, since it affects both the morphology of thesemiconductor and the charge carrier transport at the semiconductor-dielectric interface. Herewe report on the use of an alternative amorphous fluoropolymer namely Hyflon® AD (SOLVAY)as the gate dielectric in organic and hybrid transistors. Our measurements show that Hyflon® AD40 is highly transparent and an excellent insulator making it ideal for use in organic transistorsand potentially inorganic and/or hybrid electronics. In addition it is solution processable andexhibits remarkably high electrical breakdown strength. Hyflon® AD is also highly waterrepellent with an average water contact angle of 117°. The latter is higher that the valuereported for the widely used Cytop fluoropolymer. When used as gate dielectric it yields highperformance hole and electron transporting transistors with excellent operating stability. Forexample, n-channel [60]PCBM based transistors exhibit electron mobility up to 0.08 cm2/Vs whilep-channel devices based on a diF-TESADT:PTAA semiconducting blend exhibit a hole mobility up to1.5 cm2/Vs. Furthermore, when subjected to bias stress, Hyflon® AD 40 based transistors arehighly stable with small threshold shift. Hyflon® AD 40 is soluble in orthogonal, to many organicsemiconductors, fluorinated solvents and yield highly smooth films when solution cast. Because oftheir low surface roughness Hyflon AD 40 films can be used in both top and bottom-gatetransistors based on solution processed as well as thermally evaporated organic semiconductors.

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16:30 High Resolution Bilayer Resists Using Blends of Photoresists and Silicon-Containing MaterialsAuthors : Seung A Woo, and Jin-Beak Kim* Department of Chemistry, KAISTResume : We have reported several resists which contain diazoketo groups for deep UVlithography. Diazo-functionalized resists induce both photobleaching and polarity change uponexposure. Photoacid generator is not required in this system. Therefore, there are nopost-exposure delay problems such as linewidth variation due to acid diffusion and appearance ofT-top and foot profiles caused by air-borne or substrate contamination, which hinder fabrication ofnanometer-scale patterns. In this study, we propose novel photoresists using blends of polymerscontaining diazo-groups and amine-functionalized silicon compounds. Silicon-containingphotoresists are gaining increasing interest for a bilayer resist system. High resolution can beobtained because of anisotropic pattern transfer of a thin silicon-containing top layer into a thickunderlying polymer film. However, the silicon-containing photoresists have to contain severalfunctional groups for dry etch resistance, solubility change, and adhesion. Therefore, the designof the photoresists is relatively difficult and has the limits. The aim of this study is to design anew blending system that adjusts easily the properties of the imaging layer withoutpost-exposure delay problems. Using a mercury-xenon lamp in a contact printing mode, 0.2 µmline and space patterns were obtained. The results show this new platform has the potential forthe next generation resists.

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16:30 Spectroscopic investigation of pentacene molecular packing in fully operational organic thin-filmtransistorsAuthors : B.Fraboni, A.Scidà, A.Cavallini Dipartimento di Fisica, Università di Bologna, viale BertiPichat 6/2, 40127 Bologna, Italy P.Cosseddu, A.Bonfiglio, Dipartimento di Ingegneria Elettrica edElettronica, Università di Cagliari, piazza d’Armi, 09123 Cagliari, Italy and CNR-INFM S3 viaCampi 213/a 41100 Modena S.Milita CNR-IMM, Via P. Gobetti 101, 40129 Bologna, Italy M.NastasiLos Alamos National Laboratory MS-K771 Los Alamos NM 87545 USAResume : We investigated how structural differences in pentacene thin films of differentthickness affect the distribution of the electrically available states near the band-edge, allowingfor the identification of the actual thickness of pentacene layers in fully operational devices suchas organic thin film transistors (OTFT) We studied the molecular packing structure in films ofdifferent thicknesses (varying from 50nm to 300nm) with X-ray diffraction analyses. Theirrelative electronic density of states distribution (DOS) around the band-edge has beeninvestigated by Photocurrent (PC) and optical absorption spectroscopy analyses. We thusindependently monitored the increase with increasing film thickness of the Davydov splitting ofthe first absorption band, correlated to modifications in the film molecular structure and packing,when passing from a dominant “thin film” to a dominant “bulk” phase. We show how PCspectroscopy has the remarkable ability to detect modifications of the DOS distribution in a noninvasive way, thus allowing the direct study of the active semiconductor film in fully operationalorganic thin film transistors.

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16:30 Effect of annealing on the crystallographic structure of pentacene thin filmsAuthors : A. Moser(a), H.-G. Flesch(a), J. Novak(a), T. Djuric(a), A. Haase(b), R. Resel(a) (a)Institute of Solid State Physics, Graz University of Technology, Austria (b) JOANNEUM RESEARCHForschungsgesellschaft mbH, Institute of Nanostructured Materials and Photonics, FranzPichlerstrasse 30 A-8160 Weiz, AustriaResume : For successful organic thin film transistor (OTFT) technology it is necessary thattransistors are working in a broad range of temperatures. Change in temperatures may changethe crystallographic structure of the active organic layer and hence its performance. One of themost promising organic semiconductors is pentacene. To shed light on the crystallographicproperties of pentacene, temperature dependent x-ray diffraction experiments have beenperformed. Pentacene has been deposited on Si/SiOx substrates by physical vapour deposition.Two crystallographic phases are observed in these films, the surface mediated Thin-Film phase,

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and the Campbell phase. Grazing incidence x-ray diffraction has been used to investigate thethermal expansion and temperature stability of these two phases in-situ for temperatures rangingfrom 300 to 480 K. For both phases the largest expansion coefficient was found along anequivalent unit cell direction with a magnitude of approximately 1.0e-4. Remarkably theexpansion was positive into all unit cell directions for the Thin-Film phase while a negativeexpansion was found into one unit cell direction for the Campbell phase. Additionally the stabilityof the phases was determined. A complete fading of the Campbell phase diffraction features atlow temperatures shows a transformation from the Campbell to the Thin-Film phase. At highertemperatures the Campbell phase reappears revealing a transformation in opposite direction.

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16:30 Electron transport properties of some new 4-tert-butylcalix[4]arene derivatives in thin filmsAuthors : Liviu Leontie1, Ramona Danac2, Mihaela Girtan3, Aurelian Carlescu1, Alicia PetronelaRambu1, and Gheorghe I. Rusu1 Liviu Leontie, Aurelian Carlescu, Alicia Petronela Rambu,Gheorghe I. Rusu Faculty of Physics, Alexandru Ioan Cuza University of Iasi, Bd. Carol I, Nr. 11,700506 Iasi, Romania Email: [email protected]; [email protected]; [email protected];[email protected] Ramona Danac Faculty of Chemistry, Alexandru Ioan Cuza University of Iasi, Bd.Carol I, Nr. 11, 700506 Iasi, Romania Email: [email protected] Mihaela Girtan LaboratoireLPhiA, Angers University, 2, Bd. Lavoisier, 49045, Angers, France Email: [email protected] : Temperature dependences of electrical conductivity and thermoelectric power of somerecently synthesized organic compounds, 4-tert-butylcalix[4]arene derivatives, are studied.Thin-film samples (d=0.10-0.40 micrometer) spin-coated from chloroform solutions onto glasssubstrates were used. Organic films with reproducible electron transport properties can beobtained if, after deposition, they are submitted to a heat treatment within temperature range295-575 K. The crystalline structure and surface morphology of samples have been investigatedby XRD and AFM (corroborated to optical microscopy) techniques, respectively. The studiedpolycrystalline compounds show typical p-type semiconductor behavior. The activation energy ofthe electrical conduction ranges between 1.60 and 2.30 eV, while the ratio of charge carriermobilities was found in the range 0.90-0.96. Some correlations between semiconductingparameters and molecular structure of the organic compounds have been discussed. In thehigher temperature ranges (T>420 K), the electron transport in examined compounds can beinterpreted in terms of the band gap representation model, while in the lower temperaturerange, the Mott’s variable-range hopping conduction model was found to be appropriate. Theinvestigated compounds hold promise for thermistor applications.

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16:30 Vertically and horizontally aligned organic nanofiber arraysAuthors : Manuela SCHIEK 1, Kirill BORDO 1, Aghiad GHAZAL 1, Ivonne WALLMANN 2, ArneLÜTZEN 2, Frank BALZER 1, Horst-Günter RUBAHN 1 1 University of Southern Denmark, MadsClausen Institute, NanoSYD, Alsion 2, Sønderborg DK-6400, Denmark 2 Rheinische FriedrichWilhelms-University of Bonn, Kekulé-Institute of Organic Chemistry and Biochemistry, Gerhard-Domagk-Str. 1, Bonn D-53121, GermanyResume : Nanoaggregates from a custom-made phenyl-carbazole oligomer, namely2,7-diphenylcarbazole, are fabricated both by organic molecular beam deposition (OMBD) andsolution assisted wetting of porous anodic alumina membranes. The former method leads to theformation of mutually aligned nanofibers lying on the mica substrates, while the latter methodallows fabrication of arrays of closely packed upright standing nanofibers. For the OMBDtechnique, the nanofiber dimensions depend on the growth conditions. For the template wettingpossess the nanofiber dimensions are controlled by the shape of the template pores. Thenanofibers emit highly anisotropic blue fluorescence light upon excitation with UV-light. Thepolarization properties of the fluorescence light are investigated at room temperature, while thespectra are compared for temperatures ranging from room temperature down to 6 K. Themorphology of the nanofibers is examined by scanning electron microscopy and atomic forcemicroscopy. It is not trivial that the same molecular building block allows fabrication ofnanostructures using vapor deposition as well as solution assisted wetting. Most rod-likesemiconductor oligomers, which grow to nanofibers on a mica surface, are poorly soluble in allcommon solvents, which renders solution assisted wetting impossible. Therefore, for the firsttime we present a direct comparison of nanoaggregates obtained by the two different growthmethods using the same molecular building block.

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16:30 Synthesis and systematic investigation of disubstituted perylenediimides in organic field-effecttransistorsAuthors : Alexander V. Mumyatov,1 Pavel A. Troshin,1 Lubov’ Schmygleva,1 Mihai Irimia-Vladu2,N. Serdar Sariciftci2 and Vladimir F. Razumov1 [1] Institute for Problems of Chemical Physics ofRussian Academy of Sciences, Semenov Prospect 1, Chernogolovka, Moscow region, 142432,Russia. [2] Linz Institute for Organic Solar Cells (LIOS), Johannes Kepler University Linz,Altenbergerstrasse 69, A-4040 Linz, AustriaResume : Organic semiconductors are widely applied in organic electronics nowadays because oftheir low cost and ease of deposition processes (spin-coating, printing, evaporation). The searchfor high-performance, environmentally-stable n-channel materials is still a challenging task.Perylenediimides (PDIs) form an interesting group of materials that show good electronicproperties in combination with excellent environmental stability. Here we report the synthesis ofa series of eight PDI derivatives with variable length of alkyl chains attached to the PDIbackbone. These materials have been extensively purified by repetitive gradient sublimation. Theelectrical performance of the prepared materials was systematically studied in organic field effecttransistors (OFETs) using polyvinyl alcohol (PVA) and AlOx/BCB as gate dielectrics. It was shownthat the length of the side chain attached to the PDI backbone influences significantly the

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performance of the materials in OFETs. The best results were obtained using PDIs substitutedwith C7 and C8 alkyl chains. Application of AlOx/BCB as gate dielectric allowed us to fabricateOFETs operating at voltages as low as 1.0-1.5V. We believe that the developed family of easilyavailable non-toxic and remarkably stable PDI-based n-type semiconductors will find wideapplications in future organic electronics products.

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16:30 The role of aging of poly(3-hexylothiophene) solutions for spray- and spin coated organic fieldeffect transistorsAuthors : Urszula Bielecka (1,2), Petro Lutsyk (1), Krzysztof Janus (1), Stanislav Nespurek (2),Wojciech Bartkowiak (1) (1) Institute of Physical and Theoretical Chemistry, Wroclaw Universityof Technology, 50-370 Wroclaw, Poland (2) Institute of Macromolecular Chemistry, Academy ofSciences of the Czech Republic, 162-06 Prague 6, Czech RepublicResume : Organic materials potentially applicable in organic electronics are under restrictiverequirements, high charge carrier mobility being one of the most important. Thuspoly(alkylothiophenes), characterized by a relatively high hole mobility, are very attractive forthis purpose. Moreover, due to their ability to form various crystalline nanostructures, theirelectrical properties may be controlled, to a certain degree, by using different depositionmethods and processing conditions which strongly affect the polymer morphology and molecularorganization [1,2]. In this work we present the results of study on the effect of solution aging andnanofiber formation in poly(3-hexylothiophene) (p3ht) solution on the morphology and electricalproperties of p3ht thin films. Field effect transistors have been fabricated from as received andaged solutions by two deposition techniques: spin coating and spray coating [3]. Aging of thesolution resulted in nanofibers formation. Their existence rises the charge carrier mobility bymore than one order of magnitude (up to 15•10-3 cm2/V•s) for spin coated films. In sprayedsamples the increase was lower, probably due to damage of fibers during deposition. This workwas supported by European Commission through the Human Potential Programme (Marie CurieRTN BIMORE, Grant No. MRTN-CT-2006-035859) [1] J.-M. Verilhac et al., Synthetic Metals 156(2006) 815 [2] A. Salleo, Materials Today 10 (2007) 38 [3] C.K. Chan et al., Appl. Phys. Lett. 96(2010) 133304

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16:30 Self-Assembly of Poly(styrene)-block-Poly(n-butyl acrylate) diblock copolymers at air/waterinterfaceAuthors : V. Torrisi1, G.Zhavnerko2, A. Licciardello1, G. Marletta1 1Laboratory for MolecularSurface and Nanotechnology (LAMSUN), Dept. of Chemical Sciences- University of Catania andCSGI, Viale A. Doria 6, I-95125, Catania 2 Institute of Chemistry of New Materials, NationalAcademy of Sciences, F.Scoriny 36, Minsk 220141, BelarusResume : Nano- and micro-meter sized structures emerge naturally in thin copolymer films andthe formation of long-range ordered nano- and microstructures at surfaces represents one of themajor challenges in nanotechnology. Block copolymers are suitable to reach this goal because ofthe nanometer range of their molecular extensions and the diversity in which different andcomplex polymer molecules can be provided by modern synthetic chemistry, as well as the easyprocessability and microphase separation of immiscible polymer blocks. These self-assembledpatterns have been considered as lithographic masks as well as templates for the furthersynthesis of inorganic or organic structures. Such applications are made possible by exploitingcontrasts in chemical or physical properties that lead to differential etch rates or attractions tonew materials. New applications in fuel cells, batteries, and optoelectronic devices rely on theinherent properties of the blocks. All of these uses depend on the regular self-assembly of blockcopolymers over macroscopic distances. The present report is aimed to discuss the aggregationbehaviour of amphiphilic poly(styrene)-b-poly(n-butyl acrylate) block copolymers into circulardomains at air/water interface with different density depending on the ratio between two blocksand the surface pressure of transfer. The morphology and the composition of such films havebeen characterized by AFM and ToF SIMS.

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16:30 Surface oxidation dynamics of crystalline rubreneAuthors : Enrico Fumagalli, Luisa Raimondo, Leonardo Silvestri, Massimo Moret, Adele Sassella.Università di Milano - Bicocca, Department of Materials Science, Via R. Cozzi 63, Milano I-20126(Italy) Marcello Campione Università di Milano - Bicocca, Department of Geological Sciences andGeotechnologies, Piazza della Scienza 4, Milano I-20126 (Italy)Resume : Due to the high mobility values of its crystalline phase, rubrene (RUB) has anoutstanding role among organic semiconducting materials. In order to use it in the fabrication oforganic electronic devices it is necessary to grow RUB as crystalline thin films on differentsubstrates, to study the morphology and electric properties of such films and to determine theirstability in ambient conditions. When exposed to air, the surface of RUB crystals or thin-filmsundergoes a fast oxidation process, leading to the formation of RUB endoperoxide (RUB-OX). Theunderstanding of the effects of such oxidation process on thin film morphology and electrostaticproperties is then of great relevance for the development of efficient semiconductor devices. Inthis report, we determine the oxidation dynamics of epitaxially grown crystalline RUB thin filmsand RUB single crystals, and its correlation with the evolution of their morphological, structural,and dielectric properties, using a combination of Kelvin probe force microscopy, surfacemorphology measurements and phase contrast measurements, and by comparison with x-raydiffraction data and with the results of calculations of the electrostatic properties of RUB-OXlayers. This study demonstrates the formation of a “native” crystalline and ordered oxide layerover the surface of the pristine RUB film suggesting the possibility of exploiting it in thefabrication of electronic devices, in analogy with what is currently done with silicon.

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16:30 Nanoscale control of structural and electrical properties of hybrid multilayers fabricated by goldnanoparticles and diblock-copolymer templatesAuthors : V. Torrisi1, F. Ruffino2, M. G. Grimaldi2 and G. Marletta1 1 Laboratory for MolecularSurface and Nanotechnology (LAMSUN), Dept. of Chemical Sciences- University of Catania andCSGI, Viale A. Doria 6, I-95125, Catania 2Dipartimento di Fisica e Astronomia and MATISCNR-INFM, Universit?i Catania, Via S. Sofia 64, I-95123, Catania ItalyResume : The combination of solid nanoparticles (NPs) and block copolymers (BCs) can yieldcomplex composites for example for photonic and band gap materials. The specific morphologyand hence the utility of these materials depends on the copolymer architecture and on suchparameters as the size and volume fraction of the particles. Nanostructures hold the promise ofunconventional electronic behaviour of hybrid materials, due to the way in which nanostructuringmay affect the transport of electrical charge at nanoscale. Indeed, it was demonstrated that forsuitable nanostructures, quantum confinement of the electrical charge may enhance the electricalconductivity even in conventional materials which do not exhibit good performance in bulk form.Here, we present a method for the preparation of hybrid Au NPs/block copolymer multilayers(MLs). In particular, such method involves two preparation techniques: Horizontal Precipitation-Langmuir Blodgett method (BC deposition); and sputtering technique (Au NPs deposition). Thehybrid MLs have been prepared by an iterative method, that involves the sequential deposition ofBC and Au NPs film. Hybrid MLs have been characterized step by step, by chemical (XPS),morphological (AFM) and electrical point of view (I-V, ρ-T measurements) were performed. Theyexhibit characteristic electrical behaviour, involving in particular the appearance of Schottky-likeI-V behaviour depending on the annealing treatments.

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16:30 Using NEXAFS to determine the Structure-Property Relationship of a Highly-Crystalline ThiophenePolymerAuthors : T. Schuettfort, M.J. Lee, H. Sirringhaus, C.R. McNeill Cavendish Laboratory, Universityof Cambridge, Cambridge, United Kingdom;Resume : The high performance polymer poly(2,5-bis(3-alkylthiophene-2-yl)thieno[3,2-b]thiophenes) (PBTTT) has previously been studied in terms of its transistor performance andpolymer structure using X-ray diffraction and near edge X-ray absorption fine structure (NEXAFS)spectroscopy. Several different morphologies which exhibit different device performance andsurface morphologies have been reported. A recent discovery is the alignment of completelystretched backbones in films produced with the zone-casting technique. In order to investigatethe structure-performance relationship and self-ordering mechanism we analyse NEXAFS spectra,scanning transmission X-ray microscopy (STXM) and atomic force microscopy (AFM) images ofPBTTT thin films to compare with transistor performance. The surface sensitive NEXAFSmeasurements can identify the orientation of molecules through the directionality of thetransition dipole moments and has chemical selectivity on the conjugated backbone or theside-chains through the relevant transitions. Our data indicates that aligned nano-ribbons formedin zone-cast films have an altered packing geometry with reduced total energy. STXM imagesidentify the orientation of the polymer backbone due to the edge-on orientation of the thiophenerings on the substrate. This allows identifying the domain size in terraced PBTTT films and thealignment patterns of the nano-ribbons.

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16:30 Characterization of Organic Capacitors Fabricated Using All Inkjet Printing on PES SubstrateAuthors : Injun Bae(1), Kyohuk Kim (2),Jaejun Han(1), Ilsub Chung(1)(2)* (1) Information andCommunication Engineering, Sungkyunkwan University, Suwon 440-746, Korea (2)Sungkyunkwan University Advanced Institute of Nanotechnology, Sungkyunkwan University,Suwon 440-746, KoreaResume : We attempted to fabricate organic storage capacitors on polyethersulphone (PES)substrate using ink jet printing for E-paper drive circuits. Two different dielectric materials likepoly-4-vinylphenol (PVP) and poly methyl methacrylate (PMMA) were examined by varying itsthickness and w%. Silver was used as a metal electrode, and the area of the capacitor was 150um x 150 um. All the processes including metal electrodes were done using ink-jet printer. Thedielectric properties were analyzed by measuring C-V, and the physical properties including themorphologies were analyzed using optical microscope, SPM and SEM.

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16:30 The Traps Study of Organic Light-Emitting Diode with Doped Hole Transporting LayerAuthors : En-Ping Yao(1), Wei-Chou Hsu(1), Chiu-Sheng Ho(1), Yu Chang(1), E-Ling Huang(1),Ching-Sung Lee(2), Shih-jeh Wu(3), and Yu-Shen Wang(3) (1) Institute of Microelectronics,Department of Electrical Engineering, and Advanced Optoelectronic Technology Center, NationalCheng Kung University, Tainan 70101, Taiwan, R.O.C. Phone: +886-6-2757575 #62350 / E-mail:[email protected] (2) Department of Electronic Engineering, Feng Chia University,Taichung 40724, Taiwan, R.O.C. (3) Department of Mechanical and Automation Engineering,Material Science and Engineering, I-Shou University 1 Section 1, Hsueh-Cheng Rd., Ta-Hsu,Kaohsiung 84008, TaiwanResume : Organic light-emitting diodes (OLEDs) have been studied extensively in past twentyyears due to its potential applications on display and solid-state lighting. The distribution of trapsstates inside the band gap influences strongly the electrical characteristics of the devices. Severalapproaches have reported to study the trap property of semiconductor materials, such ascurrent-voltage characteristics, impedance spectroscopy, thermally stimulated current (TSC), anddeep level transient spectroscopy (DLTS). Conventional capacitance-based DLTS is not suitable tomeasure the traps of organic semiconductor materials owing to the low carrier mobility. In thiswork, we use charge-based deep level transient spectroscopy (Q-DLTS) to measure the trapcharacteristics of doped hole transporting layer in OLED device. In addition, a simple green-

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emission OLED is fabricated to study the influence of trap of hole transporting layer on OLEDperformance. For the device processing, an indium-tin-oxide (ITO)-coated glass substrate with asheet resistance of 20 ohm/sq was used as the anode for all devices in this work. The ITOsubstrate was cleaned with organic solvents in an ultrasonic bath and then treated with UV-ozoneexposure to modify surface property of ITO. Organic film was deposited by using high-vacuumthermal equipment in a background pressure of 3×10-6 Torr. A 50-nm thick N,N’-bis(naphthalene-1- yl)-N,N’-bis(phenyl)-benzidine (NPB) layer doped with X% copper phthalocyanine(CuPc) (X=0, 1, 10) was used as the active layer for the Q-DLTS measurement. On the otherhand, a simple green OLED device consisting of a 50-nm thick doped-NPB hole-transporting layerand a 60-nm thick tris(8-hydroxyquinoline) aluminum (Alq3) emitting layer was fabricated tostudy the trap effect on OLED performance. A 100-nm thick aluminum was used as cathode for alldevices in this work. The trap characteristic of organic film was performed by Q-DLTS system,supplied by SULA Technology Corp. The current density-voltage-luminance (J-V-L) and currentefficiency characteristics of the studied OLEDs were measured by using a Konica Minolta LS-100luminance meter correlating with a Keithley 2400 source meter. The photoluminescence (PL) ofthe organic films was measured by using an Ocean Optics USB 4000 spectrometer. According tothe Q-DLTS spectra for the undoped NPB layer measured under the temperature range from 290to 315 K. The charging time tc = 0.2 ms, an offset voltage V0 = 0 V, and a charging voltage Δ,V= 2 V. The Arrhenius plot derived from the Q-DLTS spectra and the slope of fitted curve indicatesthe activation energy of 0.39 eV for the undoped NPB layer. In addition, the trap concentration of9.72 × 1014 cm-3 is obtained under the long charging time. The Q-DLTS under similar conditionsexcept for the charging time tc = 0.6 ms for the 1% doping concentration NPB layer shows adecreased activation energy of 0.27 eV is obtained from the corresponding Arrhenius plot. Theinfluence of CuPc doping on molecular arrangement of NPB could be the main reason for thedecreased activation energy. In addition, the trap concentration of NPB layer is increased to 1.20× 1015 cm-3 under the 1% doping concentration of CuPc. According to the Q-DLTS spectra for theNPB layer doped with 10% CuPc measured under the temperature range from 290 to 310 K. Thecharging time tc = 0.3 ms, an offset voltage V0 = 0 V, and a charging voltage Δ,V = 2 V are usedas the measurement conditions. Similar to the case of 1% doping concentration, the activationenergy of 0.27 eV is obtained from the corresponding Arrhenius plot. Nevertheless, an obviousincrease of trap concentration of NPB layer to 7.64 × 1015 cm-3 is observed under the 10%doping concentration of CuPc. More carriers would be trapped within the NPB layer under theincreased trap concentration, which can be explained by the PL spectrum. The slight increase oftrap concentration from 9.72 × 1014 to 1.20 × 1015 cm-3 results in the small decrease of opticalintensity. On the other hand, an obvious degradation of optical intensity under the 10% dopingconcentration is observed owing to the apparent increase of trap concentration from 1.20 × 1015to 7.64 × 1015 cm-3. The influence of trap property on the OLED performance is studied by asimple green-emission OLED device. Compared to the undoped OLED device, the J-Vcharacteristic of the studied OLED with 1%-doped NPB is improved. The turn-on voltage (at 10mA/cm2) is reduced from 4.8 to 3.3 V and the maximum luminance is increased from 2716 to3755 cd/m2. The improved performance of the studied OLED device could be illustrated from theenergy-band diagram. Under the 1%-doped condition, the activation energy of trap within theNPB layer changes from 0.39 (Ea1) to 0.27 eV (Ea2). The shallow distribution of trap would bebeneficial to the transporting of hole carrier within the NPB layer and hence enhance theperformance of the studied OLED device. Because of the improved J-V and luminance properties,the maximum current efficiency of the studied OLED device is increased from 1.40 to 1.50 cd/A.However, the turn-on voltage of the studied OLED device is increased from 3.3 to 6.0 V when thedoping concentration of CuPc further increases from 1% to 10%. The main reason for thedegraded J-V performance could be result from the increase of trap concentration within the NPBlayer which retards the transporting of hole carrier. Because of the degradation of J-V property,the maximum luminance and current efficiency of the studied OLED device are reducedapparently to 895 cd/m2 and 0.40 cd/A, respectively. This work was supported by the NationalScience Council of Republic of China under the contract no. NSC 97-2221-E-006-240-MY3 and NSC99-2221-E-214-017, also would like to thank the Bureau of Energy, Ministry of Economic Affairs ofR.O.C. for financially supporting this research under Contract No. 99-D0204-6 and the LEDLighting and Research Center, NCKU for the assistance regarding measurements.

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16:30 Study of Improved Efficiency by Anode Oxidation Technique in High Color Purity of Top-EmissionWhite Organic Light Emitting DiodeAuthors : Yu Chang(1), Wei-Chou Hsu(1), Chiu-Sheng Ho(1), En-Ping Yao(1), E-Ling Huang(1),Ching-Sung Lee(2), and Shih-jeh Wu(3) (1) Institute of Microelectronics, Department of ElectricalEngineering, and Advanced Optoelectronic Technology Center, National Cheng Kung University,Tainan 70101, Taiwan, R.O.C. Phone: 886-6-2757575 #62350 / E-mail:[email protected] (2) Department of Electronic Engineering, Feng Chia University,Taichung 40724, Taiwan, R.O.C. (3) Department of Mechanical and Automation Engineering,Material Science and Engineering, I-Shou University, Kaohsiung 84008, TaiwanResume : Organic light emitting diodes (OLEDs) have been studied extensively in the past 30years owing to their potential applications to lighting and display technologies. However, theapplication of OLEDs with a conventional bottom-emission design to full-color displays usuallyrequires a complicated drive circuit, which would seriously cause the diminished pixel apertureratio (AR). The operation current density is usually increased to accommodate low AR deficits.Consequently, issues of increased fabrication cost, degraded display performance, and shortoperation lifetime seriously limited the application of bottom-emission OLEDs. A top-emissionorganic light emitting diode (TOLED) structure consisting of a reflective anode and asemitransparent cathode is a suitable alternative for full-color display applications. However,strong microcavity effects within the TOLED were observed to deteriorate the white emission

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over a broad range of the visible spectrum. Hsu et al. demonstrated a top-emission white organiclight-emitting diode (WOLED) with a CFx-coated anode and a semitransparent cathode with anindex-matching layer to relive the microcavity effect. The Commission Internationale del’Eclairage (CIE) coordinate in the top-emission WOLED is (0.31, 0.47). Kanno et al. also reportedan approach to diminish the microcavity effect in a top-emission WOLED by using hightransparency indium tin oxide as the cathode and a devised Li-doped electron-transporting layer.The device showed a white-emission CIE coordinate of (0.42, 0.39). Ag is commonly used as ananode owing to its high reflectivity at the visible-light region. However, the low work function ofAg limits the hole injection from the anode to the organic layer. Some studies have proposedmeans to reduce the energy level mismatch between the Ag anode and its neighboring organiclayers. In this work, we present a top-emission WOLED design that exhibits high color purity andimproved emission efficiency by performing Ag anode oxidation by using a plasma-enhancedchemical vapor deposition (PECVD) system. The device performance with respect to reflectivity,conductivity, and surface roughness characteristics of the Ag anode and oxidation processingparameters is also studied. The proposed top-emission WOLED design demonstrated optimumluminance and current efficiency of 10,700 cd/m2 and 1.08 cd/A, respectively. Besides, superiorwhite color purity with the CIE coordinate of (0.35, 0.33) is also achieved. To verify the formationof the AgOx layer upon the Ag anode after oxidation in PECVD, the electron spectroscope forchemical analysis is used to measure the ratio of oxygen atoms in the 1s orbital and Ag atoms inthe 3d orbital. According to the results of XSCA measurement, the oxygen content of the Ag filmis less than 0.1% without treatment. The oxidation is due to the exposure of the Ag anode in air.Then, it is increased to 2% when the anode is oxidized for 4 min at the operation power of 1 W.The oxygen compositions are further increased to 4.3 and 4.8% when the operation power isincreased to 2 and 3 W, respectively, with the same duration of 4 min. Besides, the oxygencontent is also affected by the oxidation time. The oxygen content in the AgOx layer increasestremendously from 1.6 to 21.6% as the oxidation time is increased from 1 to 6 min at the samedeposition power of 2 W. A similar study using UV ozone treatment has been reported bydetecting the binding energies of silver and oxygen in the X-ray photoemission spectroscopyspectra. According to the J-V characteristics of top-emission WOLEDs, the turn-on voltages of thedevices with treated Ag anode are decreased obviously. This implies that the hole injection isenhanced owing to the reduced energy barrier between AgOx and NPB. The current densities ofthe top-emission WOLEDs with treated Ag anode are also enhanced apparently. This indicatesthat more carriers are injected into the device to improve the luminance characteristics. Thesurface roughness property of the treated Ag anode is also essential to the device performance ofWOLEDs. It is mainly because the rough surface of the treated anode would degrade theinterfacial quality between the organic layer and the anode. This would limit the hole injectionfrom the anode to the organic layers. It is slightly increased to 1.59, 1.65, 1.53, and 1.42 nmunder the operation power/duration settings of 1 W/4 min, 2 W/1 min, 2 W/4 min, and 2 W/6min, respectively. Nevertheless, the surface roughness is increased tremendously to 2.6 nmwhen the operation power is increased to 3 W, possibly because the surface of the Ag electrodewas damaged by severe bombardment under the high operation power of PECVD. A smallvariation in surface roughness for the treated Ag anode at less than 2 W indicates that the contactproperty between the anode and the organic layer was not affected. An increased surfaceroughness of the Ag anode under the operation power of 3 W would possibly generate vacancieswithin the anode/organic layer interface to limit the hole injection property. Besides, surfaceroughness characteristics of the treated Ag anode decreased with the increased depositionduration at a lower deposition power. It is mainly because the higher oxygen composition andlayer thickness at a longer treatment time can lead to a more complete chemical formation ofthe AgOx layer. The surface flatness of the treated Ag anode is then improved. According to theJ-V-L characteristic of top-emission WOLEDs, the maximum luminance of the studied devicewithout oxidation is 206 cd/m2. It is enhanced to 9140 cd/m2 under the oxidation treatment of 2W/4 min. The corresponding current efficiency is also improved from 0.56 to 0.96 cd/A. Improvedluminance and current density characteristics are attributed to the enhanced hole injection fromthe Ag anode to organic layers after the formation of the AgOx film on the anode. However, thedevice performance is degraded to 5350 cd/m2 and 0.67 cd/A after further increasing thedeposition power to 3 W. In addition to the comparisons of the surface roughness property, asdiscussed before, one possible reason for the observed deteriorated device performance isattributed to the degradation of reflectivity of the treated Ag anode. On the other hand, thereflectance of the treated Ag anode degrades with the increased deposition power or theoxidation duration. For example, when the operation power is increased from 2 to 3 W, thereflectances under illumination wavelengths of 450 and 600 nm are degraded by 13.4 and 13.8%,respectively. Similarly, the reflectance of the treated Ag anodes are also decreased by 0.2 and1.1% at 450 and 600 nm wavelengths as the oxidation duration is increased from 4 to 6 min atthe same deposition power of 2 W. An increased oxygen content was found with increaseddeposition power or deposition duration. Therefore, the degraded reflectance characteristics ofthe treated Ag anode are mainly due to the increased oxygen content of the AgOx layer as itincreases the deposition power and treatment time. Consequently, degraded reflectance woulddegrade the light outcoupling and hence lower the luminance of the top-emission WOLED.Therefore, the oxidation processing needs to be compromised with respect to work function andreflectance characteristics of the Ag anode to obtain high luminance and current efficiency. Inaddition, the corresponding CIE coordinates of the present top-emission WOLEDs at 9 V, treatedunder deposition power settings of 0 (untreated), 2, and 3 W are (0.35, 0.33), (0.34, 0.35), and(0.34, 0.33), respectively. The color purity of the white emission of the studied top-emissionWOLED design is believed to be related to the microcavity effect. However, the EL spectra of thestudied devices under different deposition conditions indicate that the color purity of the whiteemission is not affected obviously. The above results indicate that the reflectance variation due todifferent anode treatment conditions mainly affect the light out-coupling instead of the color


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purity in the proposed devices. Superior white color purity is maintained because the studieddevices have the same organic layer structure. On the other hand, comparable improvements inthe white color purity of the studied three WOLED devices under different anode oxidationprocesses are achieved. The CIE coordinates are around (0.35, 0.33). Nevertheless, the presenttop-emission WOLED design demonstrates the best luminance and current efficiency performanceof 10,700 cd/m2 and 1.08 cd/A when treating the anode in PECVD for 6 min at 2 W. It is superiorto 9140 cd/m2 and 0.96 cd/A when the PECVD settings are 2 W and 4 min, and 7800 cd/m2 and1.0 cd/A by using the UV ozone oxidation technique. Consequently, the present WOLED designunder an optimum anode oxidation processing has demonstrated improved efficiency andsuperior color purity, which is suitable for display applications. This work was supported by theNational Science Council of Republic of China under the contract no. NSC 97-2221-E-006-240-MY3and NSC 99-2221-E-214-017, also would like to thank the Bureau of Energy, Ministry of EconomicAffairs of R.O.C. for financially supporting this research under Contract No. 99-D0204-6 and theLED Lighting and Research Center, NCKU for the assistance regarding measurements.

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16:30 Nonvolatile Memory TFTs using Printed Organic Semiconductor Active Channel and OrganicFerroelectric Gate InsulatorAuthors : Soon-Won Jung, Kang-Jun Baeg, Min-Seok Kim, Sung-Min Yoon, Kang Dae Kim, YongSuk Yang, Jae Bon Koo, and In-Kyu You Electronics and Telecommunications ResearchInstitute(ETRI)Resume : Organic non-volatile memories are the emerging research field due to its uniquecharacteristics in charge storage properties and a relatively low manufacturing cost. Conjugatedmolecules and solution processable charge storage materials enable to realize the memorydevice by simple and cost-effective solution processes such as spin coating or various graphic artprinting techniques. To realize high performance ferroelectric OFET memory, ferroelectricpolymer materials must show both robust mechanical properties as a gate dielectric and largedipole polarization as a memory element. Poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] copolymer is one of the promising materials to fulfill both properties at once. In this study,we demonstrate a low voltage operated top gated ferroelectric polymer transistor memory with ainkjet-printed organic semiconductor active channel and a poly(vinylidene fluoride-trifluoroethylene) ferroelectric gate insulator. Key features of our ferroelectric memory devicesare all-solution process and a relatively low operating voltage. The low operating voltage wasachieved by single P(VDF-TrFE) dielectric layer and the memory device typically operated a lowgate and source-drain bias below 15 V.

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16:30 Anisotropic Behavior of Performance in Solution Processed Organic Thin-film Transistor EmployingSelf-assembly of Organic Channel/Polymer DielectricAuthors : J. H. Park, Y. G. Chang, Kwang. H. Lee, and Seongil Im Institute of Physics and AppliedPhysics, Yonsei UniversityResume : We prepared a highly-performing hysteresis-free devices with batch-by-batchuniformity by blending TIPS-pentacene and insulating isotatic (i-) poly (methyl methacrylate)(PMMA), since the i-PMMA is reported to have good leakage-protecting and hysteresis-minimizingproperties. Here, we introduce “vertical flowing” technique of blend solution which isdistinguishable from the previous reports. The “vertical flowing” method provide us withelongated TIPS-pentacene crystal and allow us to fabricate highly-performing TFT on glasssubstrate, which exhibit mobility of 0.34 ± 0.03cm2/V s operating at -15V. As another part ofpresentation, we show some scientific analysis of the layered channel (TIPS small-molecule)/insulator (PMMA polymer) structure by means of UV-absorption spectroscopy, scanningkelvin probe microscope(SKPM) and mirco-photoluminescence (PL) technique. SKPM and Mirco-PLresult show that there exist different degree of crystalline structure between TIPS-pentacenecrystal and inter-crystal region. This characteristic difference renders anisotropic mobilitydifference according to whether the growth direction of TIPS-pentacene crystal is parallel ororthogonal to source/drain electrodes. Using this anisotropic characteristic of channel layer, wecould fabricate a load-resistance type inverter with the two types of TFTs (of parallel andorthogonal grown pentacene crystal channels). The inverter demonstrates a maximum voltagegain of 12 at a device supply (Vdd) of -15V.

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16:30 Stability of Solution Processed Organic Thin Fim Transistor Employing Phase-segregation ofOrganic Channel / Polymer Dielectric: Bias-stress and Interfacial Charge Trap Density of StateAuthors : J. H. Park, Y. G. Chang, Kwang. H. Lee, Kyung H. Lee and Seongil Im Institute ofPhysics and Applied Physics, Yonsei UniversityResume : A small-molecule semiconducting material, TIPS-pentacene, and insulating isotatic (i-)poly (methyl methacrylate) (PMMA), has been blended to provide reproducible reference TFTs.We prepared a highly-performing hysteresis-free device with batch-by-batch uniformity byblending TIPS-pentacene and i-PMMA. We introduce “vertical flowing” technique of blend solutionwhich is distinguishable from the previous reports. This method provide us with elongatedTIPS-pentacene crystal and allow us to fabricate highly-performing TFT on glass substrate, whichexhibit mobility of 0.34 ± 0.03cm2/V s operating at -15V. As another part of presentation, weaddress stability issue of our TFT by means of bias stress and photo-electric method. Positivegate bias leads to a positive shift in the threshold voltage, while the transfer curve moves tonegative against negative stress, indicating charge trapping is major reason of threshold voltageshift. The reference TFT shows vulnerable and irreversible behavior (deep trap related) tonegative bias stress, while robust and reversible (shallow trap related) behavior was also shownunder a positive voltage stress. The time evolution of threshold voltage is described by thestretched-exponential equation in conjunction with the time dependent analysis of sub-threshold

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slope. Photo-electric characteristic under monochromatic photon energy (ranging from 1.2 to 3.4eV) will also be discussed and quantitatively in terms of threshold voltage shift.

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16:30 Blue organic light emitting diodes with different emitting and hole-injection layer thicknessesAuthors : Chong Li (A), Wei Huang (A), Taiju Tsuboi (B) (A) Key Laboratory for Organic Electronics& Information Displays and Institute of Advanced Materials, Nanjing University of Posts andTelecommunications, Wenyuan Road 9, Nanjing 210046, China. (B) Faculty of Engineering, KyotoSangyo University, Kamigamo, Kita-ku, Kyoto 603-8555, Japan.Resume : High performance and high efficiency in organic light emitting diodes (OLEDs) dependson charge carrier distribution and charge balance. Especially the charge balance is important toachieve the long lifetime of OLED by avoiding charge leakage from the emitting layer. A numberof methods has been undertaken to achieve high carrier density and charge balance, forexample, good alignment between the Fermi level of the electrode and the correspondingtransport band of the adjacent organic layer. The electron mobility is largely different from holemobility for most organic materials, giving rise to charge imbalance. To obtain the chargebalance, it is necessary to make the electron and hole mobilities in emitting layer (EML)comparable to each other. In the present paper we report that the OLED performance such asquantum efficiency, power efficiency, luminous efficiency, operational voltage, and operationalcurrent density strongly depend on the EML thickness. The EML in the OLED consists ofblue-emitting DSA-ph (1-4-di-[4-(N,N-di-phenyl)amino]styryl-benzene) as dopant (5 wt %) anddiphenylanthracene derivative 9,10-di(2-naphthyl)anthracene (ADN) as host. The hole injectionlayer (HIL) is a 2-TNATA doped with F4-TCNQ, hole transport layer (HTL) is a 10 nm thick NPB,and the electron transport layer (ETL) is a 20 nm thick Alq3. The EML thickness was changedbetween 15, 25, 35, 50, and 70 nm, and correspondingly the HIL thickness was changed between95, 85, 75, 60, and 40 nm, respectively, i.e., the total device size from HIL to ETL was kept at140 nm. Low operational voltage was obtained from the OLED with the 15 nm thick EML. Thethreshold voltage increases with increasing EML layer thickness. The highest luminous efficiencyof 14 cd/A was obtained from the 35 nm EML, while the lowest 11 cd/A was obtained from boththe 15 and 70 nm EMLs. The highest external quantum efficiency of 6.2 % was obtained from the35 nm EML, while the lowest 4.2 % was obtained from the 70 nm EML. The highest powerefficiency of 8 lm/W was obtained from the 15 nm EML, while the lowest power efficiency wasobtained from both the 70 nm EML. Discussion is given on cavity effect by changing the EML layerthickness and also on the reason why the layer thickness gives rises to OLED performance.

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16:30 Synthesis and Characterization of a Novel Thiophene-based Semiconducting Polymer for OrganicElectronicsAuthors : Juhwan Kim1, Kang-Jun Baeg2, Dongyoon Khim1 and Dong-Yu Kim1* 1 Heeger Centerfor Advanced Materials, School of Materials Science and Engineering, Department of NanobioMaterials and Electronics, Gwangju Institute of Science and Technology (GIST), 261 Cheomdan-gwagiro (Oryong-dong), Buk-Gu, GwangJu 500-712, Korea, +Convergence Components andMaterials 2 Research Laboratory, Electronics and Telecommunications Research Institute (ETRI),138 Gajeongno, Yuseong-gu, Daejeon 305-700, Republic of KoreaResume : Since their discovery, semiconducting polymers have been attracting tremendousattention because of their suitability in a wide range of promising low-cost, flexible, andthrowaway electronic applications such as organic photovoltaic cells (OPVs), organic thin-filmtransistors (OTFTs), or radio frequency identification (RFID) tags. Therefore, a great number ofresearch and development efforts have been devoted to the field of semiconducting polymermaterials due to this high potential probabilities and broad application areas. The performance oforganic electronic device is restricted by the charge carrier mobility and energy band gap. Thecarrier mobility and band gap depend on the structural regularity and control of extendedπ-conjugation. Also, they are affected by morphological conditions. Therefore, polymersemiconductors require good chemical/physical structural properties and morphology for highperformance of electronic devices. Novel thiophene-based semiconducting polymer wassynthesized employing a coplanar unit to achieve an extention of π-conjugation and control ofband gap, and containing long alkyl side-chain part for solution processabiliy for organicelectronic applications. This polymer was synthesized via Grignard, Kumada, and stille couplingreactions. The basic material characterizations using NMR, DSC, TGA and GPC were investigated.In addition, optical and structural properties were analyzed using UV/Vis spectroscopy and XRD.We investigated a morphological change by annealing process. In this presentation, we willdiscuss on the synthesis and structural characterization of a novel thiophene-based conjugatedpolymer, and performance of electronic devices.

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16:30 Reproducibility and stability measurements of OFETAuthors : Rizwan Ahmed(1), Michael Sams(2), Mujeeb Ullah(1), Clemens Simbrunner(1), KamilaRehman(1), Günther Schwabegger(1), N. S. Sariciftci(3), Timm Ostermann(2), H. Sitter(1) 1Institute of Semiconductor & Solid State Physics, JKU, Linz Austria. 2 Research Institute forIntegrated Circuits – RIIC, JKU Linz, Austria. 3 Linz Institute for Organic Solar cells, JKU Austria.Resume : Intensive research has been done to find high carrier mobility organic semiconductors,but very little efforts were made to measure and improve the reproducibility and stability oforganic electronics devices [1-3]. We are presenting a comprehensive study concerning thereproducibility and stability. We choose C60 baser OFET to measure fabrication reproducibilityand long term stability. C60 is a high mobility n-type material and we have a lot of experiencewith this material [4,5]. We used BCB as dielectric material and C60 was deposited as an activelayer using hot wall epitaxy. For source and drain contacts, LiF and Al were used. We fabricatedseventy transistors and each transistor was measured for twenty four hours inside the glove box.

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We also extend the stability measurements to long time measurement up to fifteen days. Wereport about the fluctuations in the device parameters of all seventy transistors by comparing thetransfer characteristics, On/Off ratio of all transistors for short time and long time measurements.We found that C60 based OFET’s, show excellent reproducibility and stability. References 1. T.Someya et al; Langmuir 18, 5299 (2002). 2. Tobat P.I. Saragi et al; Synthetic Metals 148, 267(2005). 3. Tiwari, Shree Prakash et al; Journal of Applied Physics, 106, 054504 (2009). 4. MujeebUllah et al; Journal of Applied Physics, 106, 114505 (2009). 5. Mujeeb Ullah et al; Appl. Phy. Lett.96, 213306 (2010).

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16:30 An efficient and stable cathode for OLEDsAuthors : Andrea Gassmann, Christian Melzer, and Heinz von Seggern Technische UniversitätDarmstadt, Institute for Materials Science, Electronic Materials Division, Petersenstr. 23, 64287DarmstadtResume : For the realisation of long-living organic light-emitting diodes (OLEDs) with a goodperformance efficient and stable cathodes are mandatory. The objective of the present work isthe development of efficiently electron injecting and stable contacts. The current standardcathode for OLEDs LiF / Al serves as reference system. The application of a novel bilayer cathodeconsisting of a sub-nanometer thin Li3PO4 layer capped with an aluminium layer will be proved tobe a promising approach: Using a Li3PO4 / Al cathode an efficient electron injection was realizedwhich was competitive to the injection from the standard system LiF / Al. At the same time thedevices with Li3PO4 / Al cathode showed an increased lifetime. The experiments investigating themechanism behind the electron injection from Li3PO4 / Al evaluated the influence of holes onelectron injection and a possible charge-transfer doping between Li3PO4 and the organicsemiconductor. Further, the interface properties of the new cathode were analysed. These studiesrevealed that the functional principle of the Li3PO4 / Al cathode was not due to doping of theorganic semiconductor close to the cathode but rather based on the in situ formation of a dipolarinterface. Due to an interface reaction partly oriented dipoles are created causing a considerablework function lowering. The work function of the Li3PO4 / Al cathode is found to be comparable tothe work function of calcium. As a result the electron injection is promoted and an efficient andstable cathode system was developed.

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16:30 Investigation of a photoreactive polymer containing spiropyran groups aiming for an applicationin organic thin film transistorsAuthors : Lucas Hauser(a*), Stefan Kirnstötter(b), Marco Marchl (b), Egbert Zojer(b), AlexanderFian(c), Thomas Griesser(d), Wolfgang Kern(d), and Gregor Trimmel(a) (a) Institute forChemistry and Technology of Materials, Graz University of Technology, Stremayrgasse 9, A-8010Graz, Austria (b) Insitute of Solid State Physics, Graz University of Technology, Petersgasse 16,A-8010 Graz, Austria (c) Institute of Nanostructured Materials and Photonics, JoanneumResearch, Franz-Pichler-Straße 30, A-8160 Weiz, Austria (d) Institute of Chemistry of PolymericMaterials, University of Leoben, Otto Glöckel-Strasse 2, A-8700 Leoben, AustriaResume : The reversible photoreaction of spiropyrans switches the molecule between the openzwitterionic merocyanine and the closed neutral spiropyran form. This significantly impacts itsoptical properties (UV-vis spectrum, dielectric constant) as well as the polarity of the material(neutral vs. zwitterionic). As a consequence, this polymer is interesting as interfacial layer inorganic devices when aiming at tuning device properties by light. In this contribution, we presentthe synthesis of photoreactive poly(norbornene) bearing spiropyran groups and discuss thephotochemical behavior of this material. The photochemical ring opening of the spiropyran ringcan be achieved by illumination with light of 365 nm, whereas the back reaction is induced bylight of 560 nm. The photochemistry was investigated by spectroscopic methods (UV-vis, FT-IR),with cyclovoltammetry as well as with contact angle measurements. In addition the difference inreactivity can be used for selective immobilization of functional molecules. Finally, the polymerwas investigated as interfacial layer between the gate dielectric and the semiconductor(pentacene) in a bottom-gate, top contact thin film transistor. No clear change in the devicecharacteristics caused by illumination was observed; instead a very pronounced bias stress effectwas obtained in both forms, which is presumably related to the redox properties of thespiropyran. Financial support by the Austrian Science Fund FWF (S9702-N20)

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16:30 Controlling the charge transport characteristics by using mixed hole transport layer and improvedquantum efficiency in green phosphorescent organic light-emitting diodesAuthors : Sung Hyun Kim*, Kigook Song Department of Advanced Materials Engineering forInformation & Electronics, Materials Research Center for Information Display, Kyung HeeUniversity, Youngin, Gyeonggi-do 449-701, Korea [email protected] Tel :82-31-201-3344 Fax:82-31-204-2530Resume : Green phosphorescent organic light-emitting diodes (PHOLEDs) with a mixed holetransporting layer (HTL) were developed and device performances were studied depending onthe composition of mixed HTL materials with different type of host material’s type. Two holetransport materials, N, N’-di(1-naphthyl)-N,N’-diphenylbenzidine (NPB) and 4,4’,4”-tris(N-carbazolyl)triphenylamine (TCTA), were used in the mixed hole transport layer. Quantumefficiency of green PHOLEDs could be obtained by more than two times in the 3:1 mixed host ofTCTA:NPB with (4,4’-N,N’-dicarbazole)biphenyl (CBP) as host compared with that of thecorresponding single host devices.

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16:30 Patterned Modulation of the Conductivity of Polyaniline by Means of PhotolithographyAuthors : S. V. Radl (a,b), T. Griesser (a), M. Edler (a), T. Köpplmayr (a),W. Kern (a,b), T. Rath(c), G. Trimmel (c), A. Pavitschitz (d), C. Teichert (d), C. Simbrunner (e), G. Schwabegger (e ),H. Sitter (e). (a) Institute of Chemistry of Polymeric Materials, University of Leoben, A-8700Leoben. (b) Polymer Competence Center Leoben GmbH (PCCL), Rosseggerstraße 12, 8700Leoben, Austria (c) Institute for Chemistry and Technology of Materials, Graz University ofTechnology, A-8010 Graz . (d) Institute of Physics, University of Leoben, A-8700 Leoben. (e)Institute of Semiconductor and Solid State Physics, University of Linz, A-4040 LinzResume : In this contribution we present the preparation and characterization of aphotosensitive polyaniline derivative (PFANI) bearing pendant N-formamide units. An illuminationwith UV light leads to a decarbonylation reaction of the pendant N-formamide groups resulting inpolyaniline (PANI) and carbon monoxide. The photogenerated PANI can be protonatedsubsequently by a treatment with gaseous HCl acid to give the insoluble and conductiveemeraldine salt. Due to the insolubility of the protonated PANI a negative-toned image can beobtained by development with dimethylformamide. Conductivities in the range of pristine dopedpolyaniline were measured in the illuminated (and protonated) region. These photo-inducedconductivity changes were corroborated by conductive AFM measurements. It turned out that theconductivity of PFANI depends on the conversion of the N-formamide groups, which offers thepossibility of a selective adjustment of the conductivity by means of UV light. Moreover, a photo-structured polyhexaphenylene based OLED could be realized using thin films of PFANI as photo-patternable charge injection layer.

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16:30 Characterization of transparent organic light-emitting diodes depending on thickness variation oftop metal cathode and organic capping layerAuthors : Jonghee Lee*, Simone Hofmann, Mauro Furno, Michael Thomschke, Yong Hyun Kim,Bjoen Luessem, and Karl Leo Institut f?ngewandte Photophysik, Technische Universit?Dresden,D-01062 Dresden, GermanyResume : We investigate the optical characteristics of transparent organic light-emitting diodes(TOLEDs) with thickness variation of the top metal electrode and of an additional organicdielectric layer. We find that the thickness variation of the top cathode shows different influenceon bottom and top side emission, respectively. The overall efficiency which is the sum of bottomand top emission can be enhanced up to 17.7 % of external quantum efficiency (EQE) and 25.1lm/W of power efficiency (PE) at 15 mA/cm2, respectively. Furthermore, we carefully investigatethe angular distribution of bottom and top side emission separately with a spectrogoniometer.The distributions strongly differ from Lambertian and exhibit opposite trends depending on thetop metal cathode thickness. We further investigate another set of TOLEDs with different organiccapping layer (OC) thickness to understand the capping layer effect. We find that the thicknessvariation of OC strongly influences the emission properties of TOLEDs and exhibits differenttrends for top or bottom side emission. The top side EQE can be enhanced by a factor of 63%, butthat of the bottom side only by 4% compared with reference without OC. Additionally, wedemonstrate that the introduction of the OC is an effective method to control bottom to topemission ratio within a measured range from 2.87 to 6.05.

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16:30 Spin transport through spin filter and organic semiconductor hybrid tunnel barriersAuthors : Yu Jeong Bae1, Nyun Jong Lee1,Tae Hee Kim1*, Hyunduck Cho3, Changhee Lee3, LukeFleet4, Atsufumi Hirohata4, Yeong-Ah Soh4, and Gabriel Aeppli5 1Department of Physics, EwhaWomans University, Seoul, Korea, 2School of Electrical Engineering and Computer Science, SeoulNational University, Seoul, Korea 3Department of Electronics, The University of York, York, UnitedKingdom 4Department of Materials, Imperial College, London, United Kingdom 5London Centrefor Nanotechnology, London, United KingdomResume : Organic semiconductors (OSCs) have been studied recently by many researchersinterested in spintronic applications due to the possibility of making flexible products with vastlydifferent properties. More challenges in both device performance and fundamental understandingof the mechanism affecting spin-related phenomena followed Xiong et al.’s work[1]. The choice ofthe electrode material is an important issue for spin injection into the OSC. Here, we report thespin transport properties in hybrid barrier tunnel junctions, such as Fe/MgO(100))/Cu-phthalocyanine(CuPc)/Co. In order to observe the spin filter (SF) effect for electronstunneling from the Fe/MgO(100) to the Py through the CuPc barrier, the Fe(100) film wasprepared on the MgO buffered Si(100) substrate by UHV-MBE. The 5-10 nm thick CuPc films weregrown on the epitaxial MgO/Fe/MgO(100) film by the thermal evaporation technique. Interfacestructural analysis was performed by XRD, TEM and AFM. The I-V measurements were alsocarried out at different temperatures by the dc four-probe method. We observed a strongasymmetry of the I-V curves at room temperature (RT). A large MR was observed at 77K whenthe electrons tunnel from the Fe/MgO(100) to the Co through MgO/ CuPc hybrid barriers, while noMR was observed when the electrons tunnel from the Co to the Fe/MgO(100). Our results showfeasibility of spin injections with high efficiency even at RT into OSCs via a spin filter material. [1]Z.H. Xiong et al., Nature (London) 427, 821 (2004).

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16:30 COMPUTATIONAL STUDY OF THE INFLUENCE OF NANOSTRUCTURE ON THE ELECTRICALPROPERTIES OF A POLYMER LEDAuthors : Marta M. D. Ramos, Hélder M. C. Barbosa and Helena M. G. Correia, Centre of Physicsand Department of Physics, University of Minho, Campus de Gualtar, 4710-057 Braga, PortugalResume : One advantage in using conjugate polymers as the active component in optoelectronicdevices, like light emitting diodes (LEDs), is the possibility of being deposited in solution.However, several experimental studies have shown that the nanostructure of the thin film

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depends on the conditions used to deposit the polymer, since it will affect the way that the longconjugated polymer chains stack and align relative to the electrodes, creating domains withdifferent sizes and shapes. In this way, understand and control the polymer 3D nanostructure isof great importance since it will influence the efficiency of the optoelectronic device where it isused. Here we present the results obtained by us using our mesoscopic model based on ageneralized dynamic Monte Carlo method to understand how the spatial arrangement of polymerstrands affects the functioning of a polymer LED. Our results clearly show that the electricalproperties of a polymer LED (i.e. current density, charge density, internal electric field andcharge recombination) are strongly influenced by the orientation of the polymers strands relativeto the electrodes at nanoscale.

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16:30 Transport properties dependence on chromophore concentration in high efficient white polymerlight emitting diodesAuthors : Carmen Coya* 1, Angel Luis Álvarez 1, Mar Ramos 2, R. Gómez 3 and J.L.Segura 3 1Departamento de Tecnología Electrónica. Escuela Superior de Ciencias Experimentales yTecnología, Universidad Rey Juan Carlos, E-28933 Madrid, Spain. 2 Departamento de TecnologíaQuímica y Ambiental. Escuela Superior de Ciencias Experimentales y Tecnología, Universidad ReyJuan Carlos, E-28933 Madrid, Spain. 3 Departamento de Química Orgánica. Facultad de CienciasQuímicas. Universidad Complutense de Madrid, E-28040 Madrid, Spain.Resume : White polymer light emitting diodes (WPLEDs) have been recently considered one ofthe top 10 technologies of the decade [1] due to their potential energy saving, as well as theirlightness and flexible properties, seeking to replace incandescent white light sources in large areapanels. In fact, as they are solution processed, these materials have become a strategic issuewithin the solid-state lighting (SSL) context. Recently, we have demonstrated tunable emissionfrom novel poly(fluorene-altphenylene) (PFP) derivatives containing co-monomers, involvingred-emitting 1,8-naphthalimide units as pendant groups (0.0005, 0.005, 0.02 and 0.08 % wt) [2],avoiding phase separation and the formation of aggregates. We have used these polymers inWPLEDs with single-layer structure (ITO/(PEDOT:PSS)/co-polymer/Ba/Al) that showed 22.62,7.53, 47.11 and 2.93 Cd/A emission efficiency. All the devices exhibited emission at very lowdriving currents in the μA range (47 -73 μA). In spite of the naphthalimide content all polymersshowed similar electrochemical properties, with HOMO-LUMO levels of -4.93 and -2.1 eVrespectively. However, variation of naphthalimide chromophore concentration in the polymersinduces significant changes in the current-voltage response of the devices based on thesematerials. In this work, we study the naphthalimide concentration influence on the transportproperties of the material. For this purpose, we use a numerical model that includes field-dependent carrier mobility to analyze the devices current-voltage responses, which allows us toestimate the dependence of carrier mobility on polymer composition in the diodes. [1]//spectrum.ieee.org/ [2] Coya, R. Blanco, et al.Eur.Pol.J., 46,8,1778-89 (2010).

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16:30 Stability to Photo-Oxidation of Rubrene and Substituted-RubrenesAuthors : Sureeporn Uttiya (a), Luisa Raimondo (a), Marcello Campione (b), Luciano Miozzo (c),Abderrahim Yassar (c), Massimo Moret (a), Enrico Fumagalli (a), Matteo Parravicini (a), AntonioPapagni (a), Alessandro Borghesi (a), Adele Sassella (a) (a) Dipartimento di Scienza deiMateriali, Università degli Studi di Milano-Bicocca, Milano, Italy (b) Dipartimento di ScienzeGeologiche e Geotecnologie, Università degli Studi di Milano-Bicocca, Milano, Italy (c) UniversitéParis 7 – Paris Diderot, Paris, FranceResume : Rubrene (C42H28; 5,6,11,12-tetraphenylnaphthacene) has a very high charge carriermobility in solid state that is why it has become a very promising organic semiconductor forvarious device applications. Unfortunately, rubrene exhibits a rather low stability, affecting devicelifetime, because it is very prone to photo-oxidation. Due to these negative characteristics, newsubstituted-rubrenes, such as tetrafluoro-rubrene (C42H24F4) and nitro-rubrene (C42H26N2O4),were synthesized in order to limit degradation and still having good transport behaviour in solidstate. In the present work, we studied the stability of solutions and thin films of rubrene and ofthe two substituted-rubrenes in terms of first order photo-oxidation reaction. The solutions wereprepared by dissolving the molecules of interest in 1,1,2,2 tetrachloro-ethane (C2H2Cl4),whereas thin films were grown by organic molecular beam epitaxy (OMBE) under ultra-highvacuum by using SiO2 and single crystal organic substrates. Molecule degradation by reactionwith oxygen under light makes solutions become colorless, as detected by progressive decreasingof absorbance intensity, and makes thin films change their absorbance spectra. Comparing thethree molecules, we observed degradation of rubrene about one order of magnitude faster thanthat of the substituted molecules. These results underline that introduction of fluorine atoms andnitro groups leads to an enhanced stability of the rubrene to photo-oxidation.

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16:30 Spray-deposited organic thin-film transistors of small-molecule organic semiconductorsAuthors : Natalia Azarova1, Jack W. Owen1, Claire A. McLellan1, Marsha A. Loth2, EricChapman1, John E. Anthony2, and Oana D. Jurchescu1 1Department of Physics, Wake ForestUniversity, Winston-Salem, NC 27109, USA 2Department of Chemistry, University of Kentucky,Lexington, KY 40506, USAResume : We report on spray-deposition, an innovative processing technique for fabrication oforganic thin-film transistors (OTFTs), which allows for fast and low-cost deposition over largeareas, with minimal material waste. We have explored several critical factors in deviceprocessing that affect the film structure and electronic properties. These factors include thepressure of the carrier gas used in the deposition, gas-to-solution ratio, spray distance, solutionconcentration, and spray time. The OTFTs we fabricate by spray deposition of difluoro-5,11-bis(triethylsilylethynyl) anthradithiophene (diF-TES ADT) exhibit field-effect mobilities of µ =

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0.2 cm2/Vs, and current on/off ratios Ion/Ioff =10^7. This performance is comparable with thebest performance reported in devices of this material on similar substrates by using otherdeposition methods. Properties of spray-deposited acene and thiophene derivatives arepresented and discussed in the frame of correlating chemical structure with crystal packing andfilm microstructure. Our results demonstrate that spray-deposition overcomes the scalabilitylimitations encountered with other techniques, such as spin-coating and drop casting, whilemaintaining the device performance and offering a low-cost, high-throughput, fast fabricationmethod that results in remarkable transistor properties.

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16:30 Low Voltage n-Type F16CuPc Organic Thin Film Transistors (OTFTs) with High Electron MobilityAuthors : Yaorong SU and Jianbin XU* Department of Electronic Engineering, and MaterialsScience and Technology Research Center, The Chinese university of Hong Kong, Shatin, N. T.,Hong Kong SAR, China * E-mail: [email protected] : Low voltage n-type F16CuPc organic thin film transistors (OTFTs) were fabricated usingbilayer high-k metal oxides (TiOx & Al2Ox) as gate dielectric modified by ODPA(Octadecylphosphonic acid) SAM. The processing features of the high-k metal oxide dielectricinclude sol based technology, spin coating and low processing temperature (< 200oC). Theobtained bilayer dielectric had a thickness of about 40 nm, and the respective permittivities ofTiOx and Al2Ox are about 10 and 11, owing to the amorphous nature of the oxides. The bilayermetal oxide dielectric exhibited relatively low leakage current density of the magnitude of 10-6A/cm2 and a high areal capacitance of about 240 nF/cm2. To passivate the surface of hydroxylgroups, ODPA was used to modify the metal oxide dielectric, and the resultant capacitance andleakage current density were reduced to about 190 nF/cm2 and 10-7 A/cm2, respectively. n-TypeF16CuPc OTFTs composed of the dielectric exhibited the superior properties with an operationalvoltage as low as 1.5 V. The measured electron mobility, threshold voltage, and subthresholdslope are ~0.12 cm2/Vs, ~ 0.3 V and ~0.2 V/dec, respectively. The on/off current ratio of the lowvoltage n-type F16CuPc OTFTs is on the order of 104. Moreover, the low voltage n-type F16CuPcdemonstrated a small hysteresis loop and negligible threshold voltage shift. The work is in partsupported by Research Grants Council of Hong Kong, particularly, via Grant Nos. CUHK2/CRF/08,and CUHK41

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16:30 Morphologic and electronic properties of air-stable n-channel perylene based organic TFTsAuthors : Franziska Lüttich(a), Harald Graaf(a), Iulia Korodi(b), C. von Borczyskowski(a), andDietrich R. T. Zahn(b) Chemnitz University of Technology, Institute of Physics, 09126 Chemnitz,Germany, (a) Optical Spectroscopy and Molecular Physics, (b) Semiconductor Physics.Resume : We report on the influence of different preparation parameters on air-stable n-channelorganic thin film transistors (OTFTs) using DC electrical characterization as well as Atomic ForceMicroscopy (AFM) and Kelvin Probe Force Microscopy (KPFM) in dual frequency mode. Thesestudies allow the determination of output and transfer characteristics in vacuum and in anambient atmosphere. KPFM enables the evaluation of the local potential in the channel of OTFTsduring operation in an ambient atmosphere. This gives for example direct access to the contactresistance at different applied voltages. The influence of the preparation method and substratetemperature during deposition of the organic material on the investigated transistor structureswill be discussed. The investigated OTFTs were fabricated either by physical vapour depositionunder high-vacuum conditions or by solution based deposition at normal conditions onto highlydoped silicon substrates with silicon oxide as gate insulator. Changes in temperature duringdeposition or annealing after deposition are used to control the intermolecular interactions andthe morphology of the organic thin film. These parameters influence the structural and electronicproperties of the OTFT and result in changes of the charge carrier mobility due to different grainsizes and contact resistances. The observed effects indicate tuning possibilities for organic devicesin order to increase the charge carrier mobility.

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16:30 THE ORGANIC ELECTROCHEMICAL LIGHT EMITTING FIELD EFFECT TRANSISTOR BASED ONMIXTURE OF CONJUGATED POLYMER AND SOLID ELECTROLYTEAuthors : Cigdem Yumusak*, Niyazi Serdar Sariciftci** *Department of Physics, Faculty of Artsand Sciences, Yildiz Technical University, Davutpasa Campus, Esenler, 34210 Istanbul, Turkey**Linz Institute for Organic Solar Cells (LIOS), Physical Chemistry, Johannes Kepler University ofLinz, A-4040 Linz, AustriaResume : Mixed ionic/electronic conduction in conjugated organic materials –conjugatedpolyelectrolyte composites- have recently attracted much attention as charge injection/transportlayers in organic optoelectronic devices. These materials combine the optical and electronicqualities of conjugated polymers with the properties of polyelectrolytes can be modified byelectrostatic interactions. We have fabricated the organic electrochemical light emitting fieldeffect transistor (OELEFET) using a conjugated polymer MDMO-PPV (Poly[2-methoxy-5-(3′,7′-dimethyloctyloxy)-1,4-phenylenevinylene]) mixed with polymer electrolyte poly (ethyleneoxide) including lithium trifluoromethanesulfonate (Li triflate) as active layer andbenzocyclobutene (BCB) as gate dielectric. The output characteristics (source-drain currentversus the source-drain voltage) and transfer characteristics (source-drain current versus thegate voltage) of the device are reported. Orange-yellow light emission is observed from thedevice and optical properties are examined.

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16:30 The Photophysical Properties of New Merocyanine Dyes for Photonics and NanoelectronicsAuthors : V.Yashchuk1, A.Naumenko1, K.Grytsenko2, O.Tolmachov3, Yu.Slominskiy3,S.Vasylyuk1, O.Navozenko1, V.Kosach1 1National Taras Shevchenko University of Kyiv, 03601,Volodymyrs’ka Str., 60, Kyiv, Ukraine 2 Institute of Semiconductor Physics of National Academy

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of Science of Ukraine, 03650, Nauki prospect, 42, Kyiv, Ukraine 3 Insitute of Organic Chemistry ofNational Academy of Science of Ukraine, 02660, Murmanska Str., 5, Kyiv, UkraineResume : The design of new functional materials for solar energetic devices; low energysupplied sources of light (white OLEDs for lighting), basic elements for nanoelectronics requiresspecial approaches in synthesis of functional molecules as well as new special technology of thincomposite organic films obtaining. New merocyanine dyes possessed large dipole moment in thefirst singlet excited site and ability to the optical homogenic film formation by evaporationtechnology were designed and synthesized. Their photophysical properties including opticalabsorption, fluorescence, phosphorescence and Raman scattering were investigated in solutionsand films. The films of two types were studied: obtained by evaporation technique and byspin-coating. The differences of the spectral properties of these two types of films werediscussed. For some type of dyes the optical absorption spectra of solutions and films were veryclose that shows the possibility of the usage of such types of molecules in molecular nanodevices.The work in part supported by STCU grant #4570

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16:30 The impact of intrachain defects on Time-of-Flight mobility in monodisperse, low molecularweight, highly regioregular poly(3-hexylthiophene)Authors : C Tarantini (2), M. Sommer (1), S. Huettner (2), P.Kohn (2), and C McNeill (2) 1:Melville Laboratory, University of Cambridge 2: Cavendish Laboratory, University of CambridgeResume : Regioregular poly(3-hexylthiophene) (P3HT) has been extensively used as a holetransporter in organic-inorganic hybrid photovoltaic devices, as well as in Bulk Heterojunction(BHJ) solar cells. A number of past Time-of-Flight studies investigated the relationship betweenthe transport performance of regioregular P3HT and structural parameters such asregioregularity and molecular weight. The interest in regioregular P3HT is justified by reportedpower conversion efficiencies around 6% in BHJ solar cells, as well as FET mobilities as high as0.1 cm2/Vs. In this study, thin films of defect-free and one-defect, monodisperse, low molecularweight P3HT are considered, and the relationship between structural intrachain defects, andcharge transport is investigated. Low molecular weight chains of P3HT form highly orderedsolid-state films characterized by the presence of fully chain-extended crystallites. In the lowmolecular weight region (around 8.5 kDa) the differences in transport efficiency and crystallinityin solid state films of defect-free and one-defect P3HT reach their maximum. Aspects of currenttransient dispersivity, hole mobility, and room temperature diagonal disorder are descirbed in aTime-of-Flight framework, with P3HT Time-of-Flight mobilities around 10-4 cm2/Vs.

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16:30 Pentacene thin films obtained by pulsed laser deposition on Si substratesAuthors : P.Sagan, G.Wisz, M.Kuzma Institute of Physics, University of Rzeszow, Rejtana 16a,35-309 Rzeszow, PolandResume : Thin films of pentacene were deposited using a YAG:Nd3+ laser with a secondharmonic (532 nm). Three kinds of silicon substrate (flat, pyramid and plate–like) and twoorientations of substrates with respect to the pentacene plasma plume (vertical and parallel)were used. The structure of the layers formed was examined using AFM, SEM and RHEEDmethods. The lattice parameters were compared with thin films phase parameters reported byMattheus et al. The grain size distribution in respect to Si surface type was addressed. The simplemethod of control of crystalline properties of polymer films by changing the substrate orientationis proposed.

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16:30 Inkjet printed perylene diimide based OTFT: study of the effect of the mixture solvents and thepring parameters on film morphologyAuthors : Immacolata Angelica Grimaldi1,2, Mario Barra2, Anna De Girolamo Del Mauro1, FaustaLoffredo1, Fulvia Villani1, Antonio Cassinese2, Carla Minarini1. 1Italian National Agency for NewTechnologies, Energy and Sustainable Economic Development (ENEA), Portici Research Center,Piazzale Enrico Fermi 1, 80055 Portici (Naples), Italy 2Department of Physics Science, Universityof Naples Federico II, Piazzale Tecchio 80125, Naples,Italy.Resume : Recently, N-type organic thin film transistors received much attention because of thedevelopment of organic semiconductors stable under air condition, soluble in common organicsolvents and with high charge mobility. In particular, the solution processability of the organicsemiconductors allows for the selective deposition of small quantities of materials precisely bymeans of inkjet printing technique. In the present work, we report the study of the influence ofthe solvents on the morphology of a perylene diimide semiconductor (PDI-8CN2, Polyera ActivInkN1200) inkjet printed on Si (gate)/bare SiO2 (dielectric)/Au (contacts) substrates for thetransistor fabrication. Using a pure solvent, the chemico-physical mechanism that controls thedistribution of solute during the drying process is based on the “coffee-stain” effect in which mostof the material is transferred towards the drop rim where the evaporation rate is faster. If amixture of a high–boiling-point and a low–boiling-point solvents is employed, a compositionalgradient is generated inducing a Marangoni flow. The semiconductor crystalline structure and thefilm uniformity were optimized by combining the mixing ratios of the solvents and the printingparameters (drop emission frequency, drops overlapping degree, substrate temperature) thusimproving the electrical performances of the organic transistors.

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16:30 EFFECT OF THE MORPHOLOGY ON THE OPTICAL AND ELECTRICAL PROPERTIES OFPOLYCARBONATE FILM DOPED WITH ANILINE DERIVATIVES MONOMERSAuthors : Florin Stanculescu1,4, Anca Stanculescu2, Mihaela Girtan3, Marcela Socol2, OanaRasoga2 1University of Bucharest, Faculty of Physics, 405 Atomistilor Street, P.O. Box MG-11,Bucharest-Magurele 077125 Romania, 2National Institute of Materials Physics, 105 bis AtomistilorStreet, P.O. Box MG-7, Bucharest-Magurele, 077125, Romania, 3Laboratoire de Photonique

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d'Angers (LPhiA), Université d’Angers, 2, Bd. Lavoisier, 49045, Angers, France, 4 RomanianMaterials Science - Crystal Growth SocietyResume : The composite materials based on polymeric matrix and active monomeric inclusionsthat may combine the advantageous properties of both components offer an interesting researchdirection. In this work we present some comparative studies between the optical and electricalproperties of the films prepared by vacuum evaporation from some amidic monomericcompounds and the composite films prepared by spin-coating from the a polycarbonate ofbisphenol A matrix containing clusters of the some amidic monomers. Details about thecrystallinity of the films were obtained by X-Ray Diffraction and about the morphology of thefilms by SEM and AFM. We have emphasised the effect of the polymeric matrix on the propertiesof the synthesised monomers with the purpose to manipulate the local molecular environment ofthe amidic monomer for changing the physical properties of the films (optical transmission,luminescence, electrical conduction, optical non-linear phenomena such as Second HarmonicGeneration). The correlation between the morphology of the films and the optical and electricalproperties has also been investigated. Because of the nonlinear optical properties, thesematerials could be used for active applications in the optical technology (amplifiers, frequencydoublers, waveguides, quantum switches, modulator and filters).

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16:30 Influence of the crystals organization on the electrical performance of soluble pentacene thin-filmtransistorsAuthors : C. Pitsalidis, N. Kalfagiannis, N. Hastas and S. Logothetidis Lab for Thin Films-Nanosystems and Nanometrology -LTFN Department of Physics, Aristotle University ofThessaloniki, GR-541 24 Thessaloniki, GreeceResume : In recent years extensive studies have been dedicated to improve the performance ofsolution-based organic thin-film transistor (OTFT). In this work we report on the solution-processed OTFT with 6,13 bis(triisopropylsilylethynyl) pentacene (TIPS-pentacene) as an activelayer, demonstrated by drop casting process on inclined substrates, whereas two-layer gatedielectric consisting of poly(methyl methacrylate) (PMMA) on conventional thermal silicon oxide(SiO2) wafers was employed to isolate gate contact. The crystal organization of the moleculesdepends on the wetting of the substrates and the interfacial adhesion, which found to correlatewith the contact and sliding angle respectively. According a previously suggested model, adhesionstrength between the polymeric (PMMA) surface and the TIPS-pentacene was calculated. X-raydiffraction (XRD) revealed self-aligned crystals of TIPS-pentacene with highly ordered molecularstructure, whereas spectroscopic ellipsometry (SE) evaluated the electronic properties and theoptical anisotropy of the produced films. Finally electrical characteristics of our devices allow us tostudy the anisotropic behavior of charge carrier transport and the variation in field effect mobility.

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16:30 Study of charge variation due to different concentrations of CdSe-P3HT blends applied on OTFTsAuthors : Alejandra Castro-Carranza(a), Josep Albero(b), Magali Estrada(c), Antonio Cerdeira(c),Benjamín Iñíguez(a), Emilio Palomares(b) and Josep Pallarès(a) (a)DEEEiA, Universitat Rovira IVirgili; Avda. Països Catalans 26, 43007, Tarragona, Spain. (b)Institut Català d’InvestigacióQuímica ICIQ; Avda. Països Catalans 16 43007 Tarragona, Spain. (c)CINVESTAV-IPN, Av. IPN2508 Col. Zacatenco 07360, México City.Resume : Organic Thin Film Transistors (OTFTs) have been widely studied due to their potentialapplications in large area, flexible and relative low cost circuits. Different materials, structuresand technologies have been applied in order to optimize their performance. OTFTs have been alsoused as an efficient tool to get information about the organic materials applied as active layers inthese devices, i.e. transport mechanisms, mobility, density of states DOS [1]. In this paper weuse OTFTs as a tool to analyse CdSe-P3HT blends, usually applied on solar cells [2], where CdSeis present as quantum-dots with a diameter length of 3.5nm. Different concentrations of bothmaterials in the blend are analysed by means of current-voltage and capacitance-voltagecharacteristics. UMEM [3] and a compact charge and capacitance model [4] are applied on theseOTFTs characteristics in order to describe the variation of density of charge, due to the appliedpotentials on the electrodes, according to different concentrations of the CdSe-P3HT blends.Results are discussed and compared to such concentrations applied on solar cells fabrication. [1]O. Marinov, et al. J. Vac. Sci. Technol. B Vol. 24, No.5 (2006), p. 1728 [2] J. Albero et al. PhysChem Chemical Phys. Vol. 11, 42, 9644-47pp. 2009. [3] M. Estrada et al. Solid-St Electron2008,52,787. [4] A. Castro-Carranza et al. Proceedings IEEE CTFT UK 2009.

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16:30 Time-resolved investigation of solvent vapor annealing of soluble small-molecule organicsemiconductors.Authors : R Li(1), Y. Ren(1), L. Xu(1), D.-M. Smilgies(2), J. E. Anthony(3), Aram Amassian*(1)(1)Material Science and Engineering, Division of Physical Sciences and Engineering, King AbdullahUniversity of Science and Technology (KAUST), Thuwal, Saudi Arabia. (2)Cornell High EnergySynchrotron Source, Ithaca, NY, USA. (3) Department of Chemistry, University of Kentucky, KY,USA.Resume : The solvent annealing process of a series of functionalized pentacene films designedfor organic electronics and photovoltaics has been investigated by combining in situ time-resolvedgrazing incidence wide angle X-ray scattering (GIWAXS) and quartz crystal microbalance withdissipation (QCM-D). The state of the thin film, including crystallinity, molecular packing, texture,and polymorphism were determined in situ in the solvent vapor environment as a function ofmolecular design, including packing structure and functional side groups. The solvent uptake andthe rigidity/softness of the organic thin film are monitored by QCM-D. Thin films of moleculesterminated by -CF3 electron withdrawing groups dissolve more readily in organic solvent vaporenvironment, whereas molecules terminated with other groups, e.g., –CN, did not dissolve as

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easily. Our study also reveals which molecular designs undergo phase transition and indicatesthat room-temperature solvent vapor annealing is a powerful way to modify organic thin films atlow-cost and low thermal load.

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16:30 The effect of the organic active layer thickness on the pentacene-based phototransistorperformanceAuthors : A. El Amrani 1, B. Lucas 2,*, B. Ratier 2, 1 LPSMS, FST Errachidia, B. P. 509,Boutalamine, Errachidia, University My Ismail, Morocco 2 XLIM research institute, LimogesUniversity, UMR CNRS 6172, 123 av Albert Thomas, 87060 Limoges cedex, France. * Author:E-mail address: [email protected] : We have discussed the fabrication and characterization of pentacene-basedphototransistors using indium tin oxide as a transparent electrical gate and PMMA as atransparent dielectric gate. The photoelectric properties of the pentacene-based transistor withdifferent pentacene film thicknesses were characterized under ultraviolet (365 nm) illumination.Moreover, we have noticed that for the thinner pentacene films, the threshold voltage upon UVillumination was shifted from its initial value in the dark to a positive voltage by more than 16 V,whereas the shift was only 3 V for thicker films. Thus, we have obtained a responsivity of about10-2 A/W and a higher photosensitivity of 6.5 104 for thinner pentacene films, which indicatesthat the organic thin film transistors could find use in photodetector applications.

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16:30 Characterisation and control of morphology of inkjet-printed pi-conjugated polymersemiconductor thin filmsAuthors : Loke-Yuen WONG1*, Thiha YE1, Rui-Qi PNG1, Guan-Hui LIM 3, Andrew T.S. WEE1,4,Lay-Lay CHUA1,2, Peter K.-H. HO1 1Department of Physics, National University of Singapore.2Department of Chemistry, National University of Singapore. 3Department of Electrical andComputer Engineering, National University of Singapore. 4Singapore Synchrotron Light Source,National University of Singapore.Resume : Inkjet printing (IJP) is widely seen as a preferred manufacturing platform for manytypes of plastic electronic devices due to desirable stand-off and real-time responsivity. Howeverit is increasingly appreciated that ijp can result in film morphology that is fundamentally differentfrom other established methods such as spin-casting (sc) and drop-casting (dc), owing to theunique droplet deposition and drying characteristics. We will describe here a comprehensivestudy of the optoelectronic properties of a model polymer regioregular poly(3-hexylthiophene)films formed by ijp, sc and dc methods. We show: (i) there is significant differences in the (n,k)spectrum and crystallinity of the film across the bottom to the top interfaces and with thedifferent film deposition methods that can be measured by a novel dual interface variable anglespectroscopic ellipsometry methodology; (ii) there is also a significant difference in the near-edgeX-ray absorption fine structure spectra relating to differences in the packing and interaction of thefrontier chains at the bottom and top interfaces in the films. We identified the typically lowerfield-effect transistor (FET) mobility seen in large ijp films is due to pronounced crystallizationthat persists even in single-droplet FETs spectra of inkjet-printed droplets, but can be reversed bya simple post-annealing in solvent vapor. We will also describe recent work that shows the controlof film morphology that is possible in ijp through solvent quality, which provides a particularlyimportant degree of freedom for the manipulation of semicrystalline pi-conjugated polymer films.We have applied this approach to print P3HT:PCBM solar cells with good form and film thicknessprofile.

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16:30 Effect of dielectric surface modification on the charge transport properties in poly(3-hexylthiophene) (P3HT) thin filmAuthors : J.-M. Zhuo,1,2,L.-H. Zhao1 , L.-L. Chua1,2, P.K.-H. Ho2 1 Department of Chemistry,National University of Singapore 2 Department of Physics, National University of SingaporeResume : We report here, the charge transport properties of poly(3-hexylthiophene) films onvarious modified dielectric surface from hydrophilic to hydrophobic and oleophobic nature. Themobility is increased by an order of magnitude from HMDS-treated to oxygen-plasma-treatedand OTS-treated surface. Using interferogram-modulated Fourier-transform charge-modulationspectroscopy (CMS) in the IR region and NIR-optical CMS data, we present here, clear evidencethat the delocalization of the field-induced hole charges increases from HMDS-treated surface toOTS-treated and oxygen-plasma-treated surface. This is in accordance to the field-effect mobilityof the devices where the apparent activation energy increases in the order of oxygen-plasma-treated< OTS-treated< HMDS-treated. The effect is mirrored in the NIR-optical CMS data wherethe intensities of the sub-gap induced absorption features of rr-P3HT also scales accordingly inthe same sequence.

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Morphology and OPV Devices I (Joint with Symposium S) : Martin Brinkmann

08:30 Structure and Performance in Polymer/Nanoparticle Photovoltaic DevicesAuthors : Neil C. Greenham* Cavendish Laboratory, J.J. Thomson Avenue, Cambridge CB3 0HE,UKResume : Blends of inorganic semiconductor nanoparticles with conjugated polymers areattractive photovoltaic systems since control of the nanoparticle shape and size can be used tofine-tune energy levels and physical nanostructure. However, the larger-scale morphology ofthese blends can be difficult to control, and the processes of charge transfer are less well-studiedthan in polymer:fullerene blends. I will present measurements using high-angle annulardark-field electron tomography to determine the three-dimensional distribution and alignment ofCdSe nanoparticles in blends with a poly(p-phenylenevinylene) derivative. I will also describerecent transient absorption measurements which highlight the importance of both charge transferand energy transfer in these systems.

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09:00 Molecular Packing in a Polymer:Fullerene Bimolecular Crystal and Its Implications for BulkHeterojunction Solar CellsAuthors : Nichole Cates Miller* (1), Roman Gysel(1), Eunkyung Cho(2), Chad Risko(2),Dongwook Kim(2), Chad E. Miller(1,3), Lee J. Richter(4), R. Joseph Kline(4), Martin Heeney(5),Iain McCulloch(5), Michael F. Toney(3), Jean-Luc Brédas(2), Michael D. McGehee(1) 1Department of Materials Science and Engineering, Stanford University, Stanford, CA 94305, USA2 School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332, USA3 Stanford Synchrotron Radiation Lightsource, Menlo Park, CA 94025, USA 4 National Institute ofStandards and Technology, Gaithersburg, MD 20899, USA 5 Department of Chemistry, ImperialCollege, London SW7 2AZ, U.K.Resume : Polymer:fullerene bulk heterojunction solar cells have been widely studied as aninexpensive alternative to traditional silicon solar cells. Some polymer:fullerene blends, such asblends of poly(2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene (pBTTT) with phenyl-c71-butyric acid methyl ester (PC71BM), form bimolecular crystals due to fullerene intercalationbetween the polymer side chains. We will present the determination of the detailed molecularstructure of the PBTTT:PC71BM bimolecular crystal using specular x-ray diffraction,two-dimensional grazing incidence x-ray scattering, infrared absorption spectroscopy, andmolecular mechanics simulations. The unit cell reveals interesting structural features includingtwists in the polymer backbone that allow increased backbone-fullerene interactions, curvedpolymer side chains, and one-dimensional fullerene channels for electron transport. The resultsexplain previous observations regarding mobility and absorption and open the door for improveddesign of polymer:fullerene bulk heterojunction blends. We also demonstrate the ability tocontrol intercalation by tuning the size of the fullerene derivative and show how fullereneintercalation affects absorption, exciton splitting, and solar-cell performance.

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09:15 Probing the miscibility of fullerene acceptor and polymeric donor materials in bulk heterojunctionphotovoltaicsAuthors : Michael A. Brady* (UCSB), Neil D. Treat (UCSB), Louis A. Perez (UCSB), Justin E.Cochran (UCSB), Michael F. Toney (SSRL), Craig J. Hawker (UCSB), Michael L. Chabinyc (UCSB),Edward J. Kramer (UCSB)Resume : Organic photovoltaics represent potentially low-cost, solution-processable materialsfor sustainable energy generation. The concept of a bulk heterojunction relies on the separationof donor and acceptor domains to maximize interfacial area for exciton dissociation, whileretaining pathways for charge transport to each electrode. Although phase-pure domains arebelieved to exist due to phase separation of acceptor (PCBM) and donor (P3HT) components, ourresults suggest that the structure of the blend is more complex at elevated annealingtemperatures. In this work, the rapid interdiffusion of PCBM and P3HT is investigated usingdynamic secondary ion mass spectrometry and grazing-incidence wide angle X-ray scattering,illustrating the significant miscibility of PCBM within P3HT amorphous regions, especially attemperatures (150 ºC) at which devices are often annealed to improve performance. It isobserved that incorporation of PCBM within P3HT does not perturb the crystallites of P3HT. Thesolubility of PCBM in the P3HT-rich phase decreases at lower temperatures. This mixing behavioris contrasted with that of PCBM in PBTTT, a thienothiophene-thiophene co-polymer of reducedside chain density.

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09:30 Visualizing photovoltaic nanostructures with high-resolution analytical electron microscopyreveals phases in bulk heterojunctionsAuthors : M. Pfannmöller* 1, H. Flügge2, G. Benner3, I. Wacker4, W. Kowalsky2,5, R. R.Schröder1,5 1 CellNetworks, Heidelberg University, Heidelberg, Germany 2 Institute forHigh-Frequency Technology, TU Braunschweig, Braunschweig, Germany 3 Carl Zeiss NTS,Oberkochen, Germany 4 Karlsruhe Institute of Technology, Karlsruhe, Germany 5 InnovationLab,Heidelberg, GermanyResume : The efficiency of bulk-heterojunctions (BHJ) depends largely on their 3D structure atthe nanoscale. Attempts to visualize thin films of BHJs have been made using transmissionelectron microscopy. It provides nanometer resolution and the possibility for tomographic 3Dreconstructions. However, so far bright field contrast was achieved applying imaging conditions,which deteriorate resolution and, hence, reliability of image interpretation. Furthermore, imagecontrast can result from additional thickness variations, which is also often neglected. Anothermethod to distinguish materials is to exploit their spectral characteristics by visualizing materialspecific excitations. Using ultra-thin films and adapted data analysis, different excitations candirectly be linked to structure. We show that this can be realized using analytical transmissionelectron microscopy. Spectral features in spectroscopic image data were processed. Usinginformation from films of [6,6]-phenyl C61 butyric acid methyl ester (PCBM) and poly(3-hexyl-thiophene) (P3HT), and annealed BHJs of both materials, we can create morphological maps. Weapply state-of-the-art, in-column energy filtering, thorough data correction and multivariatestatistical analysis. The resulting morphology does not only consist of pure P3HT and PCBMregions at a typical size of down to several nanometers but also of a third class joining puredomains. We conclude that this is a third phase of a homogeneous blend of P3HT and PCBM.

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09:45 Effect of 2D-Delocalization on Charge Transport and Recombination in Bulk-Heterojunction SolarCellsAuthors : H. Aarnio, M. Nyman, and R. Österbacka* Center for Functional Materials, Departmentfor Natural Sciences, Abo Akademi University, Turku, Finland S. Braun, P. Sehati, and M. FahlmanDepartment of Physics, Chemistry and Biology, Linköping UniversityResume : Charge-carrier transport and recombination in thermally treated and untreated filmsof poly(3-hexylthiophene) (P3HT) and 1-(3-methoxycarbonyl)propyl-1-phenyl-[6,6]-methanofullerene (PCBM) bulk-heterojunction solar cells (BHSCs) have beenmeasured using various electro-optical techniques. The formation of lamellar structure in P3HThas a large effect on the efficiency, carrier transport, and recombination of photogeneratedcharge carriers. Heat treated P3HT/PCBM solar cells show greatly reduced carrier recombinationcompared to what is typically expected in low-mobility materials and electric-field-independentcarrier generation. In untreated films, the recombination is close to Langevin-type with electric-field-dependent quantum efficiency, consistent with the typically observed Onsager-typegeneration. In this report we present UV photoelectron spectroscopy measurements on bothregiorandom- and regioregular P3HT, and interpret the results using the Integer Charge Transfermodel. We show that spontaneous charge transfer from P3HT to PCBM occurs after heattreatment of P3HT:PCBM blends. The resulting formation of an interfacial dipole is suggested asan explanation to why geminate recombination is reduced and charge generation is increased inregioregular-P3HT:PCBM blends after heat treatment. Extensive photoinduced absorptionmeasurements using both above and below-bandgap excitation light are presented, in goodagreement with the suggested dipole formation.

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10:00 Coffee Break

Morphology and OPV Devices II (Joint with Symposium S) : Peter Mueller-Buschbaum

10:30 INVITED: Connecting Morphology with Charge Trapping and Recombination in OrganicPhotovoltaicsAuthors : David S. Ginger* Department of Chemistry, University of WashingtonResume : Film texture, or morphology, affects charge generation, transport, and recombinationin organic photovoltaics. This talk will describe the use of conductive and photoconductive atomicforce microscopy to map local variations in charge transport and photocurrent collection, and oftime-resolved electrostatic force microscopy to image charge generation, recombination, andtrap formation. Using the ability to connect local structure with trap formation and recombinationlosses in organic photovoltaics, we are testing the hypothesis that suboptimal bulk devicecharacteristics such as diode ideality factors, and fill factors can be attributed to specificnanoscale and microscale structures in films.

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11:00 The Origin of Performance Enhancement and Stability of Bulk Heterojunction Photovoltaic Devicesby AdditivesAuthors : Fengling Zhang*, Weiwei Li, Yi Zhou, B. Viktor Andersson, L. Mattias Andersson, YiThomann, Clemens Veit, Kristofer Tvingstedt, Olle Inganäs, and Uli Würfel. Department ofPhysics, Chemistry and Biology (IFM), Linköping University, SE-581 83 (Sweden), FreiburgMaterials Research Centre, Stefan-Meier-Str.21, Freiburg 79104 (Germany), Fraunhofer Institutefor Solar Energy Systems, Heidenhofstr. 2, 79104 Freiburg, GermanyResume : How 1,8-diiodooctane (DIO) enhances performance of polymer solar cells based onpolymer HXS-1 and fullerene [6,6]-phenyl C71-butyric acid methyl ester (PC71BM) is scrutinizedwith several techniques by comparing devices or blend films spin-coated from dichlorobenzene(DCB) to those from DCB/DIO (97.5:2.5 v/v). Morphology of blend films is examined with atomicforce microscopy (AFM), transmission electron microscopy (TEM) and electron tomography (3-DTEM), respectively. Charge generation and recombination is studied with photoluminescence, andcharge transport with field effect transistors. The morphology with domain size in 10-20 nm and

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vertical elongated clusters for facilitating charge transport and decreasing recombinationachieved in DCB/DIO films are the main reasons for enhancing power conversion efficiency (PCE)from 3.6% (without DIO) to 5.4% (with DIO). A one year inspection shows no significant impactof DIO on the shelf-stability of the solar cells.

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11:15 Probing the influence of molecular orientation on planar heterojunction solar cell performanceAuthors : Barry P. Rand*, David Cheyns, Bjoern Niesen, Karolien Vasseur, Bregt Verreet, JanGenoe, and Paul Heremans imec, Kapeldreef 75, B-3001 Leuven BelgiumResume : The asymmetry inherent to many organic molecules leads to a high sensitivity ofabsorption, mobility, and charge transfer to the orientation of molecules within films and atheterojunctions. However, the impact on solar cell performance has been largely overlooked.Here, we conduct a systematic and in-depth study of simple bilayer cells composed of zincphthalocyanine (ZnPc)/C60, and compare devices with the typically deposited standing upconfiguration to those with ZnPc lying flat (confirmed with XRD). The lying flat ZnPc leads to anincrease in all solar cell parameters (fill factor (FF) by 17%, open-circuit voltage by 11%, andshort-circuit current (Jsc) by 45%) to raise efficiency from 1.7% to 3.2%. Spectral response(EQE) reveals a ≈,70% increase in ZnPc signal, accompanied by a 15% reduction in C60. This,together with reflection measurements which show that the absorption of ZnPc increases by 15%while the C60 signal remains unchanged, implies that the molecular orientation has an impact oncharge transfer. AFM shows that the lying flat configuration has a donor/acceptor interface areaincrease of 8%, which cannot account for the Jsc increase. Significantly, we find that the lying flatconfiguration leads to an increase by more than 2 times in mobility probed in the verticaltransport direction, and via EQE modeling and photoluminescence quenching, we find that theexciton diffusion length increases from 6 to 10.7 nm, accounting for the large increase in FF andJsc.

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11:30 Stochastic Modeling of the 3D Morphology in Hybrid Polymer-ZnO Solar CellsAuthors : O. Stenzel* (a), R. Thiedmann(a), H. Haßfeld(a), L.J.A. Koster(b), S.D. Oosterhout(b),S.S. van Bavel(b), M.M. Wienk(b), J. Loos(c), R.A.J. Janssen(b), and V. Schmidt(a) (a) UlmUniversity, (b) Eindhoven University of Technology, (c) University of GlasgowResume : The efficiency of polymer solar cells critically depends on the intimacy of mixing of thedonor and acceptor semiconductors used in these devices to create charges and on the presenceof unhindered percolation pathways in the individual components to transport holes andelec-trons. For different thicknesses of the photoactive layer, the 3D morphology of hybrid solarcells consisting of poly(3-hexylthiophene) as the donor and ZnO as the acceptor has beenre-solved in the nanometre range by tomographic transmission electron miscroscopy (TEM) .Subsequently, a stochastic model has been developed which describes the morphologicalstructure of these TEM images rather well. The model has been validated by comparing theefficiency of exciton quenching for real and simulated data, respectively. Furthermore, the modelcan be used to generate virtual photoactive layers of hybrid solar cells in order to identifymorphologies with improved efficiency.

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11:45 Interdigitating Nanoelectrodes as a Tool to Investigate Drying Effects in Polymer Organic SolarCellsAuthors : Felix Stelzl* (1,2), Jan Schulz-Gericke (2), Edward Crossland (3), Sabine Ludwigs (3)and Uli Würfel (1,2) (1) Freiburg Materials Research Center FMF, Stefan-Meier-Str. 21, 79104Freiburg, Germany (2) Fraunhofer Institute for Solar Energy Systems ISE, Heidenhofstrasse 2,79110 Freiburg, Germany (3) Institute for Macromolecular Chemistry, University of Freiburg,GermanyResume : Controlling the morphology of Bulk Heterojunction Polymer Organic Solar Cells (OSCs)is one of the key parameters in their successful fabrication. We present a method to examine theinfluence of the drying parameters of the photoactive layer (blend). We fabricated OSCscomposed of P3HT:PCBM in a setup with vertical electrodes (parallel to the direction of theincoming light) which are deposited on a nanostructured substrate prior to the deposition of thephotoactive materials. This allows for the application of a voltage during the deposition andsubsequent drying of the blend material. We found that this voltage is not only crucial for thefunctioning of the OSC, but determines as well the polarity of the open circuit voltage, regardlessof the materials used for the electrodes. This behaviour could be explained by an electricallyinduced separation of the blend materials, leading to enrichment of the donor material at thepositive pole and the acceptor material at the negative pole with respect to the drying voltage.We conducted furthermore experiments on planar, conventional setups like solvent annealing ofOSCs and adding extra layers of pure materials to confirm the hypothesis obtained with thenanoelectrode setup. Additionally we performed numerical simulations using a finite elementmethod to support the theory that the utilization of a drying voltage, and with this an electricfield, offers a way to separate the components of polymer solar cells.

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12:00 INVITED: Semiconductor block copolymers and brushes for OPVsAuthors : Andreas Lang, Ruth Lohwasser, Michael Sommer, Guodong Fu, Mukundan Thelakkat*Applied Functional Polymers, University of Bayreuth, 95440 Bayreuth, GermanyResume : We demonstrate the chain of control on all length scales - from molecular tomesoscopic to macroscopic - in fully functionalized semiconductor block polymers using theself-assembly principle. These materials are capable of exhibiting thermodynamically equilibriumnanostructures suitable for photovoltaic applications. This contribution covers the design,synthesis and properties of some novel semiconductor homopolymers and block copolymersusing modern methods of polymerization such as NMRP, RAFT, GRIM etc. The versatility of these

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methods was enhanced by combining these polymerization techniques with click chemistry. Forexample, the complex semiconductor polymer architecture was extended by combining RAFTpolymerization and click chemistry tools to get janus-type nanoobjects based on block copolymerbrushes. First defined polymer brushes of vinyl triphenylamine were grown from apoly(trimethylsilyl propargyl acrylate)-block-poly(hydroxyethyl acylate) via RAFT, followed byclicking azide functionalized perylene bisimide acrylate brushes on to the deprotected propargylacrylate units. This allows the preparation of a diblock polymer brush, comprised of vinyltriphenylamine and perylene bisimide acrylate brushes resulting in monodisperse nanoobjectsfrom single diblock polymer brush particles. In summary a variety of polymer architectures andtheir application in devices are also given.

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12:30 Lunch

Advanced Imagaing Techniques : Paolo Samorí

14:00 INVITED: Real-time in-situ electrical, morphological and structural characterisation of organicsemiconductors grown in high-vacuumAuthors : Fabio Biscarini*,1 Arian Shehua,1 Santiago Quirogaa,1 Andreas Strauba,1 StefanoCasalinia,1 Francesco Borgattia,1 Mauro Murgiaa,1 Cristiano Albonettia,1 Fabiola Lisciob,2 SilviaMilitab.2 1. CNR-Istituto per lo Studio dei Materiali Nanostrutturati (ISMN), Bologna Italy 2.CNR-Istituto per la Microelettronica e i Microsistemi (IMM), Bologna ItalyResume : The combination of in-situ real-time techniques for studying growth phenomena onoperating organic field effect transistors (OFET), will be shown for different conjugated molecularsemiconductors: pentacene, sexithienyl, and perylene derivatives. By a combination of structural(grazing incidence X-ray diffraction and X-ray reflectivity), morphological (variable temperatureSPM in ultra-high-vacuum) and electrical characterisation techniques [1] in ad-hoc designedsetups [2], it is possible to directly infer the correlation among the different properties, achievinga deep insight on the influence of the very first organic semiconductor layers on the chargetransport and injection processes. Earlier controversial observations can be unified. Relevantobservables of the growth (e.g. dimensionality of growth mode, scaling exponents, diffusivitycoefficients, energy barriers), distribution of charge carriers across the semiconductormonolayers, the effective Debye length, percolation pathways, and subtle electronic effects atthe organic/metal interface can be extracted from the experimental data via growth models. Wethank P. Stoliar, A. Scorzoni, P. D'Angelo, F. Schreiber for their collaboration. This work issupported by EC FP7 ONE-P Large Scale project no. 212311. [1] A. Shehu et al. Phys. Rev. Lett.104, 246602 (2010). [2] S. Quiroga et al., Rev. Sci. Instr. in press (2010).

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14:30 Macroscopic & nanoscale charge transport investigation on P3AT: from semi-crystalline film tosingle nanofiberAuthors : JC Bolsee* (a), WD Oosterbaan (a), L Lutsen (a,b), D Vanderzande (a,b), J Manca (a,b)a Hasselt University, Institute for Materials Research, Wetenschapspark 1, 3590 Diepenbeek,Belgium b IMEC-IMOMEC, Wetenschapspark 1, 3590 Diepenbeek, BelgiumResume : Recently, a lot of attention has been devoted towards the fabrication ofone-dimensional organic crystalline nanostructures like the poly(3-alkylthiophene) (P3AT)nanofibers (NFs). They offer an ideal tool for investigating charge transport in organicsemiconductor. In this presentation, we discuss our recent results on these NFs (in the form offilm, web and single NF) and compare them to less ordered P3AT semi-crystalline films. OFETsperformed as a function of alkyl side chain length, and dielectric surface suggest that thegoverning factor for optimal charge transport is the molecular orientation at the interface andnot, as could be expected, the crystallinity degree. Moreover, low temperature measurementsindicate that charge transport is well described by the mobility edge model. Single NF wasstudied by conductive atomic force microscopy (CAFM). CAFM is a current sensing AFM techniquewhere the tip acts as a mobile top electrode. Two different geometries were used. In the firstgeometry, we study the transport perpendicularly to the NF in a diode structure. I/V spectroscopyshow a space charge limited current transport and gives a mobility of~10-5cm2/Vs. In the secondgeometry, the transport along the NF is studied by placing the NFs in a transistor structure.Topography and current maps are simultaneously recorded and matched perfectly: gatemodulated current flowing through one single NF is perfectly resolved. Mobility measurementalong one NF is in progress.

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14:45 Characterization of organic thin films by friction force and transverse shear microscopyAuthors : Q. Shen1*, M. Kratzer1, M. Edler2, T. Griesser2, W. Kern2, C. Teichert1 1 Institute ofPhysics, Montanuniversitaet, 8700 Leoben, Austria 2 Institute of Chemistry of PolymericMaterials, Montanuniversitaet, 8700 Leoben, AustriaResume : For producing low cost thin film transistors and photoelectric components, organic thinfilms can be applied as an important class of materials. This contribution will be dedicated to themechanical characterization of organic thin films by friction force microscopy (FFM) andtransverse shear microscopy (TSM). First, we report on the FFM investigation of an organicphotosensitive molecule, which can be photoisomerized by UV light through a contact mask toachieve photochemically patterned surfaces. The pattern could be visualized by ex-situ FFMmeasurement due to significant friction contrast on different surface terminations [1]. Fordetecting real time surface modification during UV-illumination, a quasi-in-situ FFM measurementhas been applied. A clear change of friction force during illumination can be revealed. Secondly,we apply TSM to reveal crystallographic domains in ultrathin polycrystalline organicsemiconductor films [2]. Using TSM, the elastic anisotropy in different crystallographicarrangements (individual domains) can be revealed [3]. The recorded TSM image can beconsidered as a crystallographic orientation map to obtain information on shape, size, boundary

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and crystallographic orientation of domains in our para-hexaphenyl 6P film grown by hot wallepitaxy on silicon oxide substrate. Using home-made sample rotation device, TSM measurementsat same position have been recorded at each 5 degree. The corresponding data reveal that TSMis very sensitive to relative orientation between the scan direction and the crystallographicdirection, and using TSM rotated measurement, the absolute orientation of domains could bedetermined. This work is funded by Austrian Science Fund within NFN “Organic Thin Films”Projects S9707, S9702. [1] G. Hlawacek, et al., J. Chem. Phys. 130 (2009) 044703 [2] G.Hlawacek, et al., Science. 321 (2008) 108. [3] K. Puntambekar, et al., Adv. Funct. Mater. 16(2006) 879.

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15:00 Imaging Nanostructures in Organic Semiconductor Films with Scanning Transmission X-raySpectro-MicroscopyAuthors : Benjamin Watts* 1, Christopher McNeill 2, and Jörg Raabe 1 1 Swiss Light Source, PaulScherrer Institut, 5232 Villigen, Switzerland. 2 Cavendish Laboratory, University of Cambridge, JJ Thomson Ave, Cambridge CB3 0HE, United Kingdom.Resume : Thin films of organic semiconducting materials are of increasing technologicalimportance in optoelectronic devices such as LEDs, lasers, FETs and solar cells. However, themorphology of such films is complex, often displaying three dimensional composition structure ormolecular alignment effects. The structure of the polymer film incorporated into a device canstrongly affect its performance characteristics, e.g. via the connectedness of polymer domainsand to the device electrodes, or due to anisotropic material properties due to molecularalignment. Scanning transmission x-ray spectro-microscopy (STXM) has been demonstrated to bean excellent tool for the study of organic materials due to its high spatial resolution (down toabout 20 nm) and strong contrast based on a variety of spectroscopic mechanisms. In particular,tuning the probing x-ray beam to resonances in the near edge x-ray absorption fine structure(NEXAFS) spectra provides a mechanism for molecular-structure based contrast which is a verypowerful tool for studying blends of organic components. A further advantage of STXM is thatintelligent use of spectroscopic information allows quantitative compositional analysis of imagedareas. Recent work at the PolLux STXM has demonstrated two new developments in the imagingof thin organic films: simultaneous surface and bulk imaging via an additional channeltron TEYdetector, and molecular orientation mapping via anisotropic near edge resonances.

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15:15 Digging for the dewetting reconstruction at the organic interface: A low temperature STM study of6P on Cu(110)Authors : Margareta Wagner*, Stephen Berkebile, Alexander Fleming, Thomas Ules, GeorgKoller, Falko P. Netzer, Michael G. Ramsey Institute of Physics, Surface and Interface Physics,Karl-Franzens University Graz, A-8010Resume : From studies of the film growth dynamics sexiphenyl (6P) films on Cu(110) enhanced1-dimensional diffusion has been observed. We have postulated this results from a dewettingreconstruction that occurs on completion of the 3rd molecular layer [1]. Here with the STM atcryogenic temperatures the nature of this reconstruction has been explored. Moreover, byapplying molecular manipulation we have been able to “dig” down through several molecularlayers to the Cu interface. The 3rd layer molecules in the reconstruction which we argued toprovide channels for the observed 1-D diffusion are observed as one-dimensional strings oftwisted molecules. The regular spacing of the strings suggests a reconstruction. Removing thesestrings and 2nd layer molecules reveals that the highly ordered and densely packed 1stmonolayer of planar flat lying molecules on Cu(110) has been reconstructed with edge-on planarmolecules incorporated into it. Thus the reconstruction is not an organic surface reconstructionper se but a reconstruction that reaches down to the molecule-Cu interface. This work has beensupported by the by the Austrian Science Foundation (FWF) within the National Research Network“Interface Controlled and Functionalized Organic Films” and the ERC Advanced Grant “SEPON”.REFERENCES [1] Fleming A. et al, “PEEM of the Temperature Dependent Pre-nucleation Dynamicsof Sexiphenyl Molecules Deposited on Cu(110)”, Phys. Chem. Chem. Phys., in press

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15:30 Coffee Break

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X-ray Characterisation of Organic Semiconductors (Joint with Symposium M) : Michael Ramsey

08:30 INVITED: Real-time studies of organic semiconductor growthAuthors : Frank Schreiber*, Universitaet TuebingenResume : After a short introduction to the concepts of thin film growth we will explain differentstrategies to real-time observations of growth using X-ray scattering and optical techniques.These enable us to better understand the mechanisms of film growth, the evolution of structuresand imperfections, as well as the appearance of transient structures and transformations, whichwould be missed in post-growth studies. Possible other effects and challenges to a theoreticaldescription concern orientational transitions of the molecules, anomalous roughening, andchanges of the lattice parameter during growth. We will also demonstrate how the opticalproperties evolve and how they are related to the structure. We will discuss how the opticalproperties are determined by the different coupling contributions (interlayer, intralayer, andlayer-substrate). Our approach is quite general and applicable to many different materials, butexamples will be mostly shown based on work on organic semiconductors, which are applied inorganic opto/electronic devices: A. C. Dürr et al, PRL 90 (2003) 016104; B. Krause et al, EPL 65(2004) 372; S. Kowarik et al, PRL 96 (2006) 125504; D. Zhang et al, PRL 104 (2010), 056601; U.Heinemeyer et al, PRL 104 (2010), 257401); A. Hinderhofer et al, EPL 91 (2010) 56002. Thework was performed in collaboration with S. Kowarik, A. Gerlach, A. Hinderhofer, and C. Frank,as well as other groups including staff at the ESRF, namely O. Konovalov and F. Zontone.

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09:00 Exploring thickness dependent texture and crystallinity of P3HT thin films using complete polefiguresAuthors : Leslie H Jimison*, Scott Himmelberger, Jonathan Rivnay, Alberto Salleo, Department ofMaterials Science, Stanford University Michael F Toney, Stanford Synchrotron RadiationLightsourceResume : The influence of interfaces and confinement on polymer film microstructure has been ahotly researched topic for decades. This is especially interesting for the case of semicrystallinesemiconducting polymer films where film thickness may approach the crystallite size and chargetransport is strongly dependent on the film microstructure. In this work, we introduce a novelmethod to collect X-ray diffraction-based pole figures of organic thin films. The pole figures allowfor the first time quantitative characterization of film texture and degree of crystallinity.Furthermore, intensity arising from perfectly oriented crystallites nucleated exclusively at thesubstrate surface can be differentiated from bulk-nucleated crystallite intensity. We study films ofP3HT as a function of thickness on OTS treated and untreated silicon oxide. As film thicknessdecreases, texture improves and the overall degree of crystallinity decreases. Interestingly,regardless of surface treatment, as the thickness is reduced, the crystallinity of the bulk of thefilm reduces monotonically. In contrast, the population of substrate-nucleated crystallites remainsunchanged until the film thickness matches the characteristic crystallite size (~10 nm), at whichpoint the population increases 4-fold. The implications of the drastic thickness-controlledstructural change on charge transport in thin film transistors will be discussed.

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09:15 New insights into the crystal structure of poly(9,9’-dioctylfluorene-co-benzothiadiazole)Authors : W. Porzio*, A. Rapallo, ISMAC-CNR via E. Bassini 15 20133 Milano Italy L. Barba, G.Arrighetti C. IC-CNR Trieste, SS 14 km 163.5 34012 Basovizza (Ts) Italy C.R. McNeill CavendishLaboratory, University of Cambridge J J Thomson Ave Cambridge, CB3 0HE (United Kingdom)Resume : Poly(9,9’-dioctylfluorene-co-benzothiadiazole) (F8BT) has been widely studied andused in optoelectronic devices, e.g. LED, FET, and solar cells [1-3]. However, the full crystalstructure together with molecular orientation in thin films, as used in devices, has not beencompletely determined despite previous efforts combining structural, spectroscopic, and ab-initiotechniques [4,5]. Here we employ a recently developed variable-cell direct space method [6]with an additional Rietveld minimisation to determine the structure of F8BT from x-ray diffractiondata taken of powder and thin film (<100 nm thick). Preliminary findings on the unit cell andmacromolecule conformations will be presented and discussed within the context of themonoclinic system. REFERENCES [1] D. Kabra, M. H. Song, B. Wenger, R. H. Friend, H. J. Snaith,Adv. Mater. (2008) 20, 3447. [2] L.L. Chua, J. Zaumseil, J. F. Chang, E. C.W. Ou, P. K.H. Ho, H.Sirringhaus, R. H. Friend, Nature (2005) 434, 194 [3] J. J. M. Halls, A. C. Arias, J. D. MacKenzie,W. Wu, M. Inbasekaran, E. P. Woo, R. H. Friend, Adv. Mater. (2000) 12, 498. [4] C. L. Donley, J.Zaumseil, J. W. Andreasen, M. M. Nielsen, H. Sirringhaus, R. H. Friend, J.S. Kim, J. Amer. Chem.Soc. (2005) 127, 12890. [5] A. Van Vooren, J. S. Kim, J. Cornil Chem. Phys. Chem. (2008) 9 989.[6] A. Rapallo J. Chem. Phys. (2009) 131, 044113

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09:30 In-situ GISAXS study of metal electrode growth on semiconducting organic filmsAuthors : Martin A. Niedermeier* (1), Ezzeldin Metwalli (1), Volker Körstgens (1), Jan Perlich (2),Adeline Buffet (2), Mottakin Abul Kashem (2), Kai Schlage (2), Ralf Röhlsberger (2), Stephan V.Roth (2), Peter Müller-Buschbaum (1); (1) Physik Department, E13 - Chair of FunctionalMaterials, Technische Universität München, James-Franck-Strasse 1, 85747 Garching, Germany,(2) HASYLAB at DESY, Notkestrasse 85, 22603 Hamburg, GermanyResume : In the fast developing field of organic electronics thin metal films play a huge role asthey are commonly applied as electrode materials. A well defined organic/metal interface iscrucial for a good overall device performance. For a deeper understanding of this interface,information about the morphology and the incorporation of the electrode material into theorganic film is essential. However, so far only little fundamental knowledge on this topic isavailable [1]. For our work we used grazing incidence small angle X-ray scattering (GISAXS) witha very high time resolution. With this powerful technique we are able to study the growth of anelectrode in-situ. A commonly used model system for photovoltaic applications is chosen,consisting of a noble metal being deposited on an organic semiconducting film. Taking advantageof the high time resolution, we perform a real time investigation with GISAXS of the latermorphology changes during the growth process of the metal electrode. Additionally,investigations about enrichment layers of the electrode material into the organic thin film aredone using X-ray reflectometry (XRR). With these investigations we obtain a good fundamentalunderstanding of the electrode/organic semiconductor interface. [1] G. Kaune, et al., ACS Appl.Mater. Interfaces. 2009, 1(12), 2862-2869

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09:45 Structure and stability of a self-assembled monolayer for organic electronicsAuthors : H.-G. Flesch, A. Moser*, O. Werzer, E.C.P. Smits, S. G. J. Mathijssen, FatemehGholamrezaie, H.J. Wondergem, S.A. Ponomarenko, D.-M. Smilgies, G. Hlawacek, Q. Shen, C.Teichert, P. Puschnig, R. Resel, D.M. de Leeuw Institute of Solid State Physics, Graz University ofTechnology, Austria Molecular Electronics, Zernike Institute for Advanced Materials, University ofGroningen, The Netherlands Dutch Polymer Institute, Eindhoven, The Netherlands EnikolopovInstitute of Synthetic Polymer Materials, Russian Academy of Sciences, Moscow, Russia CHESSCentre, Cornell University, New York, USA Institute of Physics, University of Leoben, AustriaChair of Atomistic Modelling and Design of Materials, University of Leoben, Austria PhilipsResearch Laboratories, Eindhoven, The NetherlandsResume : In organic electronics the use of self-assembly is one promising approach to high yieldand reproducibility in device fabrication. Thin film transistors have been built from aquinquethiophene self assembled monolayer with a yield of one and accordingly integratedcircuits like bit generators could be realized [E.C.P. Smits et al., “Bottom-up organic integratedcircuits”, Nature 455, 956-959 (2008)]. Two elements of the molecule are crucial for themonolayer formation and the electronic properties. First the monofunctional anchoring groupwhich avoids uncontrolled polymerization and second the high tendency of quinquethiophene toform nice lateral crystallographic order. It is the first system reported with a long range orderedself-assembled monolayer formed on SiO2. The formation of monolayers has been followed byatomic force microscopy and x-ray reflectivity. The in-plane order of the monolayer has beeninvestigated by grazing incidence in-plane diffraction which reveals three nicely pronounced Braggrods already in the submonolayer state. A rectangular unit cell is deduced with up-right standingmolecules which are packed in a herrinbone pattern. Several irreversible effects are observed byheat treatment: a phase transition where the molecules are tilted 13° towards the b-axis of theunit cell is found after a heat tratment at 400K. In-situ experiments reveal that thecrystallographic order is lost above 520K. The self assembled monolayer remain in an amorphousstate until 620K followed by a desorption of the self-assembled monolayer until 880K

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10:00 Coffee Break

Thin-film Growth I : Norbert Koch

10:30 INVITED: Growth models for organic molecular films based on density functional theoryAuthors : Peter Puschnig*, Dmitrii Nabok, Lorenz Romaner, Claudia Ambrosch-Draxl, Chair forAtomistic Modelling and Design of Materials University of Leoben, AustriaResume : It is shown how density functional theory (DFT) contributes to the understanding ofthe thin film growth of organic semiconductors thereby revealing their structural and electronicproperties at surfaces and interfaces. Here, the focus is on the rod-like moleculespara-sexiphenyl (6P) and sexithiophene (6T) starting from monolayers up to multilayers onmetallic and non-metallic surfaces. As a starting point, cohesive and surface energies of bulkcrystals [1] and the adsorption energies on metal substrates are presented [2]. Thisdemonstrates the importance of van der Waals forces whose proper treatment is the scope ofcurrent developments in DFT. For the deposition of 6P and 6T on mica, simulations show that thegeometric structure of the substrate surface determines molecular adsorption sites andorientations thereby explaining experimentally observed needle directions [3]. For the adsorptionof 6P on amorphous mica, we study the formation of critical clusters which are lying flat on thesurface and transform into islands of standing molecules after the incorporation of furthermolecules [4]. Further deposition of molecules leads to terraced mounds due to the presence of astep-edge barrier whose nature and size is clarified by our calculations in good agreement withexperiment [5]. [1] Nabok et al., PRB 77, 245316 (2008). [2] Sony et al., PRL 99, 176401 (2007).[3] Simbrunner et al., JACS (accepted). [4] Potocar et al., PRB (accepted). [5] Hlawacek et al.,Science 321, 108 (2008).

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11:00 Spectroscopy and Microscopy of Organic Layers and NanocrystalsAuthors : P. Zeppenfeld*, L.D. Sun, Th. Wagner, D.R. Fritz, and H. Zaglmayr Institute ofExperimental Physics, Johannes Kepler University Linz, AustriaResume : We report on the investigation of organic layers, thin films and nanocrystals usingReflectance Difference Spectroscopy (RDS), Photo Electron Emission Microscopy (PEEM) andFluorescence / Laser Scanning Confocal Microscopy (LSCM). The combination of these methodsenables us to monitor the growth in-situ and in real-time (RDS, PEEM) and to explore thecorrelation between the structure and morphology of the organic films with the electronic andoptical properties at a microscopic scale (PEEM, LSCM). For instance, if the PEEM is operated witha He UV-lamp, local UPS spectra from the grown films can be obtained. Likewise, fluorescenceand local photoluminescence images recorded with the LSCM can be overlaid with AFM images ofthe very same crystallites in order to study the influence of different molecular configurations(orientation, crystalline vs. amorphous structures) or defects on the emission properties.Examples will be shown for sexithiophene (6T) and rubrene grown on different single crystallinemetal surfaces or mica.

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11:15 Pre-Nucleation Dynamics of Organic Molecule Self-Assembly Investigated by PEEMAuthors : A. J. Fleming*, S. Berkebile, F. P. Netzer and M. G. Ramsey, Surface and InterfacePhysics, Karl-Franzens Universität Graz, Universitätsplatz 5, 8010 Graz, AustriaResume : When molecules are deposited on a surface many dynamic phenomena occur prior tonucleation. We will show that control over these pre-nucleation processes may be an essentialrequisite for the growth of ordered, high quality molecular crystals suitable for the organicelectronics industry. Our detailed study by Photoemission Electron Microscopy (PEEM) examinesthe three growth processes: pre-nucleation, nucleation and 3D growth, of a technologicallyrelevant organic molecule, para-sexiphenyl (6P). By applying a combination of experimentalmethods with PEEM to 6P deposited on Cu (110) 2 x 1 – O [1] and Cu (110) [2], we canaccurately monitor in real time a) deposition quantities, b) pre-nucleation layer filling, c) dynamicsurface density redistributions during layer filling, d) nucleation and induced meta-stable layerde-wetting, e) post-nucleation molecular layer reconstructions and f) structural changes tomolecular crystals as they grow. Furthermore, measurement of diffusion anisotropies of 6Pdiffusing on different molecular layers reveals the morphology of the layer. Measured nucleationenergies are also shown to reliably indicate which type of critical nucleus forms. Many of theseprocesses exhibit temperature dependences which can be examined and used to determine ageneral model of the growth process of 6P molecular crystals. [1] Fleming et al., J. Phys:Condens. Matter 21 (2009) 445003 [2] Fleming et al., Phys Chem. Chem. Phys (2011) DOI:10.1039/c0cp01516d.

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11:30 Crystal Growth of Para-sexiphenyl on Clean and Oxygen Reconstructed Copper(110) SurfacesAuthors : J. Novák* (1), M. Oehzelt (2,3), S. Berkebile (3), M. Koini (1), T. Ules (2), G. Koller (2),T. Haber (1,2), R. Resel (1), and M. G. Ramsey (2); (1) Institute of Solid State Physics, GrazUniversity of Technology, Austria; (2) Institute of Physics, Karl-Franzens University Graz, Austria;(3) Institute of Experimental Physics, Johannes Kepler University Linz, Austria.Resume : We show that a slight modification of substrate can be crucial for organic thin filmgrowth. We studied para-sexiphenyl (6P) thin films grown by molecular beam expitaxy attemperature of 300 K on Cu(110) and Cu(110)-(2x1)O surfaces. Structure of the films wasstudied in-situ and ex-situ by X-ray diffraction methods, NEXAFS, LEED, and scanning probemethods. It is found that, for Cu-O and Cu(110) a single and a double wetting layer is formed,respectively, which then act as a template for the subsequent 3D crystal growth. For bothsubstrates the orientation of the long molecular axes of the 6P molecules in the first layers isconserved within the thin crystalline films grown on them. The main difference between bothsystems is that on Cu-O the first monolayer assembles in a structure similar to that of a 6P bulkplane which can be easily continued by crystallites grown on top of them, while on the Cu(110)surface the 6P mono- and bi-layer differ substantially from the bulk structure. The bi-layer formsa complex periodically striped phase. For thin 6P films on Cu-O, 6P(20-3) crystal plane is parallelto the substrate surface. Here, 6P molecules are stacked in layers and demonstrate only one tiltof the mean molecule plane with respect to the sample surface. On clean Cu(110), a morecomplex 6P(-629) plane is parallel to the substrate surface and seems to be a consequence of thesuper-molecular long-range periodicity of the second molecular layer striped phase.

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11:45 Large scale modeling of organic molecular beam epitaxyAuthors : Thomas Roussel*,1 Lourdes F. Vega1,2 1 - Institut de Ciència de Materials deBarcelona, Consejo Superior de Investigaciones Científicas. (ICMAB-CSIC). Campus de la UAB,08193 Bellaterra, Spain 2 - MATGAS Research Center (Carburos Metálicos/Air Products, CSIC,UAB). Campus de la UAB, 08193 Bellaterra, Spain *Corresponding Author e-mail:[email protected], phone: +34939929975, fax:+34935929951.Resume : To simulate the self-assembly of large flat-molecules (i.e. more than 50atoms/molecule), the computational effort required increases rapidly with the number ofmolecule, and drastically when their number of atom is consequent. We have implemented a gridinterpolation technique[1], which provides transferability to many organic molecules and metalsurfaces[2]. A fine balance of weak lateral molecule-molecule interactions and stronger molecule-substrate interactions governs their thermodynamic properties, nucleation and growthmechanisms. To model the organic monolayer adsorption with statistical mechanics approach, theinternal degrees of freedom of the molecules and the substrates are frozen. By pre-calculatingtheir interactions along their azimuthal orientations and intermolecular distances, we perform fullGrand Canonical Monte-Carlo calculations of thousand of molecules (systems of ~105 atoms). We

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first focus the presentation on a study case: Metal-Phthalocyanines-Halogenated adsorption onmetal-transition surfaces. To demonstrate the transferability of the approach we will providesome other examples (Di-indenoperylene (DIP) on Au and Cu) and their bi-molecular stability.We will show the consequence of edges on the metal surface on the resulting structure. This workis supported by the Spanish Government under NANOSELECT CSD2007-00041 project [1]Mannsfeld, S.C.B.; et al. Modern Phys. Let. B, 20, 11, 585 (2006) [2] Heinz, H.; et al. J. Phys.Chem. C, 112, 17281, (2008)

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12:00 INVITED: Growing Epitaxial Heterojunctions of Organic SemiconductorsAuthors : Adele Sassella* Department of Materials Science Universty of Milano Bicocca via Cozzi53 20125 Milan, ItalyResume : Nucleation and growth of organic films is driven by weak van der Waals interactions atthe film-substrate interface, while lattice commensurism between overlayer and substrate playsa marginal role with respect to the case of inorganic materials. Epitaxial organic layers, i.e.layers with crystalline order over macroscopic areas and with well defined textural orientations,can be obtained by organic molecular beam epitaxy (OMBE) using organic single crystals assubstrates. Indeed, in this case the organic-organic heterojunctions show a clear preferentialorientation of the overlayer with respect to the substrate, originating from the coincidence ofmolecular corrugations of substrate and overlayer crystal surfaces. Here, focusing on theprototypical film/substrate system a-quaterthiophene/tetracene(001), but also considering otherexamples, the experimental study of the structural, morphological, and optical properties oforganic-organic heterostructures, with the support of empirical force field simulations,demonstrates how OMBE growth may lead to highly oriented, crystalline semiconductorheterojunctions. The mechanism of orientation of the crystalline layers is being revealed as themost common in the field of low molecular weight organic semiconductors, and it may beconsidered a powerful tool for the optimization of the device structure, e.g. in transistors andsolar cells.

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12:30 Lunch

Thin-film Growth II : Frank Schreiber

14:00 Changes in optical absorption during growth of organic thin filmsAuthors : Harald Graaf* (a), Christopher Keil (b) and Derck Schlettwein (b); (a) ChemnitzUniversity of Technology, Institute of Physics, 09126 Chemnitz, Germany (b) Institute for appliedphysics, Justus Liebig University Gießen, 35392 Gießen, GermanyResume : Optical properties of organic thin films depend on different parameters. Orderedintermolecular interactions dominate spectral changes and energy diffusion within these systems.Beside of these intermolecular interactions irregularities in the organic material and in thesubstrate can act as trap for the excited state which lowers the energy migration and changesespecially the emission properties. The substrate surface can additionally influences the opticalcharacteristics without any energy transfer process. This can be seen in absorptionmeasurements taken during the growth of such thin films. Here a red-shift of the lowest energytransition with increasing film thickness can be obtained. In the literature different explanationsare given: decrease in dimension of coupled aggregates [1], quantum confinement of the layer[2], missing nearest neighbour approximation [3] and microscopic polarizability [4]. We will showrecent results on different organic materials with comparable optical properties in solution butdivers characteristics in the bulk. Also the influence of the substrate on the red-shift will bepresented and discussed with regard to the suggested models. [1] Chau et al. J.Phys.Chem. 97(1993) 2699 [2] Shen et al. Phys.Rev.B 55 (1997) 10578 [3] Heinemeyer et al. Phys.Rev.Lett.104 (2010) 257401 [4] Beckers et al. J.Phys.:Condens.Matter 10 (1998) 1721

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14:15 Rubrene-based crystalline heterostructuresAuthors : L. Raimondo* (1), E. Fumagalli(1), M. Campione(2), M. Moret (1) , A. Borghesi (1), A.Sassella (1) (1) Dipartimento di Scienza dei Materiali, Università degli Studi di Milano Bicocca, ViaCozzi 53, I-20125 Milan, Italy (2) Dipartimento di Scienze Geologiche e Geotecnologie, Universitàdegli Studi di Milano Bicocca, Piazza della Scienza 4, I-20126 Milan, ItalyResume : The fine control of morphology, structure and degree of order of organicheterostructures is a fundamental issue in the field of organic semiconductor thin films in view ofdevice applications. The understanding of the mechanisms driving the growth of highly orderedsemiconductor phases is indeed a crucial requisite for the integration in thin film devices wheredisorder and structural defects represent the first cause of poor device performances (field-effecttransistor, photovoltaic cell, etc…). Here, we report on the physical properties of multilayerorganic heterostructures grown on an insulating organic single crystal (potassium hydrogenphthalate, KAP) by organic molecular beam epitaxy. The heterostructures are built up by twoorganic semiconductors, namely alpha-quaterthiophene (4T) and rubrene (RUB). The latter is aparticularly relevant material in the field of organic electronics due to the high charge carriermobility displayed in the single crystal form. Despite the poor propensity of RUB to grow onKAP(010) surface with a crystalline structure, we will demonstrate that the combination with 4Tdrives a spontaneous formation of crystalline RUB films. In particular, by changing the sequenceof the deposited layers on KAP (RUB on 4T or viceversa) or by co-depositing the same molecules,the growth dynamics of RUB changes interestingly and structural transitions can take place asdeduced by atomic force microscopy and optical spectroscopy studies.

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14:30 INVITED: The role of perpendicular and parallel momentum in early stages of pentacene growthwith SuMBDAuthors : S.Gottardi1,2, Y. Wu1, T. Toccoli2, M. Tonezzer2, S. Iannotta3 and P. Rudolf*1 1)Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, NL-9747 AGGroningen, The Netherlands 2) IFN-CNR, Instituto di Fotonica e Nanotecnologie-Sezione diTrento, Via Sommarive, 18 I-38050 Povo, Trento, Italy 3) IMEM-CNR, Istituto Materiali perElettronica e Magnetismo Parco Area delle Scienze, 37/a, I-43100 PARMA, ItalyResume : We report a systematic atomic force microscopy study of pentacene sub- andmonolayer morphologies on SiOx/Si, resulting from deposition with supersonic molecular beams(SuMBD) of different kinetic energy and incidence angle for different substrate temperatures.During these early stages of growth, we found that the kinetic energy and the momentum of theimpinging molecules play a key role in determining the monolayer morphology. When pentacenecollides with SiOx , it looses energy through different mechanisms. The perpendicular momentumdetermines the formation of the initial nuclei: increasing the component of the kinetic energyassociated with the momentum perpendicular to the surface, E , fewer molecules needed for theformation of stable nuclei. Higher E also favours a higher island density but smaller islands. Thekinetic energy associated with the momentum parallel to the surface, E//, influences processeswhere surface-molecule interaction is important. High values of E// decrease the stickingcoefficient but favour the formation of more compact (less fractal) islands, better for therealization of ordered films. The substrate temperature in turn influences both the energydissipation and the re-desorption of molecules since both need a surface phonons to intervene.SuMBD gives the possibility to optimize the growth processes of organic molecules by selectingboth components of the kinetic energy and choosing the right substrate temperature.

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15:00 Nucleation of para-hexaphenyl on amorphous mica surfacesAuthors : T. Potocar1, S. Lorbek2, L. Tumbek1, Q. Shen2, D. Nabok3, G. Hlawacek4, P.Puschnig3, C. Ambrosch-Draxl3, C. Teichert2, A. Winkler*1 1) Institute of Solid State Physics,Graz University of Technology, Petersgasse 16, A-8010 Graz 2) Institute of Physics, University ofLeoben, Franz-Josef Strasse 18, A-8700 Leoben 3) Chair of Atomic Modelling and Design ofMaterials, University of Leoben, Franz-Josef Strasse 18, A-8700 Leoben 4) Physics of Interfacesand Nanomaterials, MESA+ Institute of Nanotechnology, University of Twente, 7500 AE Enschede,The NetherlandsResume : Organic thin films have attracted enormous interest due to their importance fororganic electronics. Nevertheless, there is still considerable lack in the basic understanding of filmformation. In this contribution we focus on the initial stages of film formation of para-hexaphenyl(6P) on amorphous muscovite mica(001). Whereas on as-received mica the 6P molecules formneedle-like islands, which are composed of flat lying molecules, on a sputter modified micasurface the 6P molecules form dendritic islands, which are composed of standing molecules. Themain question addressed in this work concerns the formation of the critical islands and thedevelopment of the size and shape of the islands in the sub-monolayer regime. For this purposewe deposited 6P by OMBE in UHV onto the sputter modified surface and investigated the layer bythermal desorption spectroscopy and atomic force microscopy. From the island size and capturezone distribution, as obtained from AFM images, we determined the critical island size, being 2and/or 3 molecules. From the island density as a function of surface temperature and evaporationrate we were able to determine the pre-exponential factor for surface diffusion and the bindingenergy of the critical nucleus. The experimental data could be corroborated and complementedby molecular-dynamics simulations using the simulated annealing method. The calculationsshowed that the critical clusters are lying flat on the surface, but transform into islands ofstanding molecules after the incorporation of further molecules.

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15:15 Characterization of perfluoropentacene thin films on alkali halide substrates via transmissionelectron microscopyAuthors : B. Haas*1, A. Beyer1, W. Witte1, T. Breuer2, G. Witte2, W. Stolz1 and K. Volz1 1Material Sciences Centre, Structure and Technology Research Laboratory, Philipps UniversityMarburg, Hans-Meerwein Strasse, 35032 Marburg, Germany 2 Department of Physics, PhilippsUniversity Marburg, Renthof 7, 35032 Marburg, GermanyResume : Perfluoropentacene (PFP), the perfluorinated sibling of the well-known p-typesemiconductor pentacene, exhibits an inversion of the charge carrier distribution and constitutesa promising organic n-type semiconductor. Thin PFP films were grown onto cleavage planes ofpotassium chloride (KCl) and sodium fluoride (NaF) substrates via organic molecular beamdeposition (OMBD). The films consist of needle-like islands which are epitaxially ordered due to aclose similarity between the b-vector of the PFP lattice and lattice parameters of the alkali halidesurfaces but exhibit different molecular orientations. We investigated the samples usingtransmission electron microscope (TEM) micro diffraction, which enabled us to determine thecrystal orientation of submicrometer-sized regions, hence providing information on localorientation correlations. In addition, the self-similar substructure of the needles has beenanalyzed using TEM dark field and bright field techniques, as well as high-resolution imaging.Intensity scans of the transmitted and diffracted electrons provide thickness information,complementary to the topography obtained by AFM. The influence of different substrates on thesubstructure and its implications on the understanding of the thin film formation will be discussed.

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15:30 Influence of the source/drain metallization scheme on the organic semiconductor growth andelectrical performance of pentacene thin film transistors with low cost bottom contactsAuthors : Robert Müller*†, Steve Smout†, Cédric Rolin†, Jan Genoe†, and Paul Heremans†‡ †imec, Kapeldreef 75, B-3001 Leuven, Belgium ‡ KULeuven, Department ESAT, Kasteelpark

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Arenberg 10, B-3001 Leuven, Belgium * [email protected] : Current state of the art organic electronic circuits are usually based on polycrystallinep-type pentacene (P5) bottom-gate bottom-contact (BG-BC) organic field effect transistors(OFETs) [1]. For the circuits to reach practical speeds, their OTFTs have to reach mobilities ≥0.1cm2/(V.s) at short channel length (L ≤10 µm) [2], which are typically achieved with thiol-treatedplain gold source/drain BCs [3]. Unfortunately the high gold prize prevents low-cost applicationsof these organic circuits. This work reports on P5 OFETs (L = 5 and 10 µm) with low-cost metallicbilayer BCs made of a few nm thick gold on top or beneath a thicker aluminum layer. Bothconfigurations are characterized by scanning electron- and atomic force microscopy, with specialattention to the P5 growth in the region of the metal/dielectric interface were charge injectionoccurs. Short channel OFETs with metallic bilayers achieve saturation mobilities sufficient for highspeed circuit applications (0.20 cm2/(V.s)) close to those of reference OFETs with gold BCs (0.40cm2/(V.s)), but below 20% of the initial metal costs. This work was performed in a collaborationbetween IMEC and TNO in the frame of the HOLST Centre. Financial support of the EC-fundedproject Polaric (FP7-247978) is acknowledged. [1] K. Myny et al., Solid-State Electron. 53 (2009)1220 [2] D.M. De Leeuw et al., IEDM Tech. Dig. (2002) 293 [3] S. De Vusser et al., Appl. Phys.Lett. 88 (2006) 10350

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15:45 Coherent Random Lasing in Amorphous Thermally Evaporated Organic Thin Films: Characteristicsand ImplicationsAuthors : S. Kéna-Cohen* (a), S. Din (b), S. Heutz (b), P. Stavrinou (a), D.D.C.Bradley (a), S. A.Maier (a) (a) Department of Physics, (b) Department of Materials Imperial College London,London, SW7 2AZ, U.K.Resume : Guest-host films based on Forster energy transfer from the green host tris(8-hydroxy-quinolinato)aluminum (Alq3) have formed the archetype small-molecule active gain medium formore than a decade. In this work, we demonstrate coherent random lasing in 250-nm thick filmsof Alq3 doped with 4-dicyanomethylene-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran (DCM)and 4-dicyanomethylene-2-tert-butyl-6-(1,1,7,7-tetramethyljulolidin-4-yl-vinyl)-4H-pyran(DCJTB). The films exhibit lasing thresholds <100 uJ/cm2. To our knowledge this is the firstobservation of random lasing in thermally evaporated films and this result has importantimplications for previous laser and amplified spontaneous emission reports in these material sets,which were observed well above the random lasing threshold. Random lasing is observed under avariety of excitation conditions and namely under direct excitation of either the Alq3 host (355nm) or the dopant (532 nm). The resolution-limited laser lines possess FWHMs < 0.05 nm andmanifest very little shot-to-shot variation. We have also observed a power law dependence of thelasing threshold with excitation area consistent with previous theoretical predictions of randomlasing in weakly scattering films. The random-lasing characteristics appear to be intrinsically-related to the underlying morphology of the amorphous Alq3 host. This is evidenced by the strongdependence of the laser characteristics on the excitation area and host material.

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16:00 Coffee Break

Poster Session II : Chris McNeill and Michael Ramsey

16:30 Morphology control of P3HT:PCBM thin filmsAuthors : F. Reisdorffer, O. Haas, P. Le Rendu, T.-P. Nguyen. Institut des Matériaux Jean Rouxel,Université de Nantes, CNRS. 2 Rue de la Houssinière, 44322 Nantes Cedex 3- France.Resume : The efficiency in organic solar cells depends greatly on control of the devicemorphology. For poly(3-hexylthiophene) (P3HT) - [6-6]-phenyl-C61-butyric acid methyl ester(PCBM) bulk heterojunction blend, the theoretical efficiency limit is ~ 11% [1] for cells made witha P3HT:PCBM and the best value reported for organic devices is only ~ 7 % [2]. To increase thecharge dissociation and hence the conversion efficiency, one approach is to control theorganisation of the layer by combining the solvent with the quality of the polymer. In this study,we have examined the changes in morphology of P3HT:PCBM films obtained by mixing PCBM withtwo types of P3HT polymers (of different purity and region-regularity) in mixtures ofchlorobenzene and toluene solvents with different ratios. The films have been analysed bydifferent spectroscopic techniques (FTRaman, FTIR, UV-Vis, Photoluminescence, XPS, AFM, SEM,and XRD. Two different organizations of the layer bulk have been observed depending on thecombination of P3HT polymer and the solvent. High quality P3HT polymer used withchlorobenzene provided the best film morphology, with PCBM layer on the top, while films madeof low quality P3HT polymer with toluene as a solvent showed disordered surface withaggregations of P3HT polymer chains. The results suggest that the solvent use together with thepolymer quality are essential parameters impacting the P3HT:PCBM thin film morphology, andhence the performance of devices. [1] L. J. A. Koster, V. D. Mihailetchi, P. W. M. Blom, Appl. Phys.Lett. 88 (2006) 093511. [2] Y. Liang, Z. Xu, J. Xia, S.T. Tsai, Y. Wu, G. Li, C. Ray, . L. Yu, Adv.Ener. Mater. 22 (2010) E135.

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16:30 Backgrounds of dye film structure formation in vacuumAuthors : K.Grytsenko, P. Lytvyn, T. Doroshenko, M. Serik, Institute of Semiconductor Physics,pr. Nauki 41, Kyiv, 03650, Ukraine, O.Tolmachev, Yu.Slominskii, Institute of Organic Chemistry, 5Murmanska str., Kyiv, 02660 Ukraine, S.Schrader, University of Applied Sciences Wildau,Bahnhofstrasse, 15745, GermanyResume : Thin films of fluorinated azo-dyes, stillbenes and polymethines were obtained byevaporation and condensation in vacuum. The influence of dye chemical structure, substrate typeand temperature on solid film morphology was systematically studied with optical spectroscopy insitu and AFM. Depending on the rate between termodynamics and kinetics, the amorphous,crystalline or nano-structured morphologies were obtained. Change of dye end and side groups

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varies its film structure. Tuning the side groups, it is possible to control morphology and opticalproperties of the films.

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16:30 Solvent induced morphology in polymer-based systems for organic photovoltaicsAuthors : Matthias A. Ruderer1, Shuai Guo1, Robert Meier1, Hsin-Ying Chiang1, VolkerKörstgens1, Johannes Wiedersich1, Jan Perlich2, Stephan V. Roth2, Peter Müller-Buschbaum1 1Physik-Department Lehrstuhl für Funktionelle Materialien, Technische Universität München,D-85747 Garching, Germany 2 HASYLAB at DESY, D-22603 Hamburg, GermanyResume : Photoactive semi-conducting polymers have shown to be interesting candidates forphotovoltaics due to their high absorption coefficient, easy processibility, mechanical flexibilityand low costs. Nevertheless there are stringent constraints in device fabrication due to the shortexciton diffusion length, i.e. the charge carrier separation has to occur in this length scale (onorder of 10 nm). Therefore the structure of the polymer film is crucial [1, 2]. The alteration ofseveral fabrication parameters, like the chemical structure of the used polymers, the type of theapplied solvent and post production treatments, allow two optimize the morphology andtherefore the performance of an organic solar cell [3]. In this study we investigate the influenceof the used solvent on the nanoscale morphology of P3HT:PCBM bulk heterojunction films.Besides imaging methods such as AFM, the advanced scattering techniques X-ray reflectivity andgrazing incidence small and wide angle X-ray scattering (GISAXS and GIWAXS) reveal a fullunderstanding of the inner film structure on molecular to mesoscopic length scales. It is foundthat the choice of solvent has direct influence on the lateral and vertical material arrangementand therefore on the device performance. Spectroscopic measurements complement thestructural information. 1. Ruderer, et al; Chem.Phys.Chem. 10, 664 (2009) 2. McNeill, et al;Adv.Funct.Mat. 19, 3103 (2009) 3. Ruderer and Müller-Buschbaum; Soft Matter, submitted (2010)

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16:30 Development of new dyes for chemical binding and formation of complex nanostructures byevaporation in vacuumAuthors : K.Grytsenko, P.Lytvyn, T. Doroshenko, M. Serik, O. Navozenko, Institute ofSemiconductor Physics, pr. Nauki 41, Kyiv, 03650, Ukraine, O.Tolmachev, Yu.Slominskii, Yu.Briks,Institute of Organic Chemistry, 5 Murmanska str., Kyiv, 02660 Ukraine, S.Schrader, University ofApplied Sciences Wildau, Bahnhofstrasse, 15745, GermanyResume : Evaporable dyes able to form covalent bond with substrate were developed andsynthesized. Their films were deposited in vacuum. The influence of dye chemical structure,deposition conditions and substrate on solid film morphology and optical properties wassystematically studied. Oligomerization and co-polymerization of dyes with some polymers alsowere studied. Stable functional organic films were obtained

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16:30 Nanoscale morphology development in polymer:fullerene photovoltaic blends during solventcasting and thermal annealingAuthors : Tao Wang, Andrew J Pearson, Alan D F Dunbar, Richard A L Jones, David G Lidzey,Department of Physics and Astronomy, University of Sheffield, Sheffield, S3 7RH, UKResume : Organic photovoltaics (OPVs) are promising solar energy conversion devices owing tothe advantages of low cost, light-weight, solution-processability and mechanical-flexibility. In anoptimized bulk-heterojunction (BHJ), OPVs based on an electron accepting fullerene and anelectron-donating conjugated polymer undergo phase-separation into a network-like structure.Following the absorption of light, the excitons created can diffuse to an interface betweenelectron accepting and donating components and undergo dissociation into an electron and ahole. Such separated charges can then be extracted via appropriate charge-conductionpercolation pathways. Photovoltaic blends based on poly(3-hexylthiophene) (P3HT) and[6,6]-phenyl C61-butyric acid methyl ester (PCBM) can be used to create devices with powerconversion efficiency of 4 to 5%. This work concerns monitoring the evolution of the nanoscalemorphology during the initial formation and post thermal annealing stages of a P3HT:PCBMphotovoltaic blend thin film. The physical processes that are identified during these investigationsare related to device efficiencies. After casting from solution, P3HT can organize into orderedcrystallines, and PCBM molecules will also aggregate to form nanocrystals. The crystallization ofthe P3HT and PCBM phases leads to enhanced optical absorption, charge separation andincreased hole mobility. Control of the nanoscale phase separation and crystallization is critical indetermining device efficiency. Previous work to determine the effect of nanoscale morphology onOPV performance has necessarily explored the structures developed in thin-films after they havebeen prepared. We have however used in-situ grazing incidence X-ray scattering andspectroscopic ellipsometry to monitor the evolution of P3HT crystallization in P3HT:PCBMphotovoltaic blends during their drying process after solvent casting. We identify three stages infilm drying: (I) rapid solvent-evaporation and slow-crystallization, (II) slowed solvent-evaporation and rapid crystallization, and (III) slow solvent-evaporation and slow crystallization.The P3HT assembles into ordered crystalline lamellae through heterogeneous nucleation once thesolvent volume-fraction in the wet film falls below 50% as a result of evaporation. The rate ofP3HT crystallization is initially rapid, but slows when the solvent volume fraction falls below 20%.We found that the degree of P3HT crystallinity in a P3HT:PCBM blend is dependent on a numberof parameters including the solvent evaporation rate and the casting temperature. We observeda self-annealing (i.e. a reduction in kinks, twists, distortions etc) of crystal defects during theP3HT crystallization process, with the characteristic lamella spacing in the P3HT crystallitesdecreasing while crystal domains grow. The morphology of an “as-cast” P3HT:PCBM blend ishowever not ideal and such untreated films perform poorly when fabricated into OPV devices. Toaddress this, the power conversion efficiency of a device can be enhanced using a variety ofpost-deposition treatments such as thermal annealing, solvent annealing and control of the

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thin-film drying rate. We further studied the evolution of structure and optoelectronic propertiesof P3HT:PCBM photovoltaic thin film blends upon thermal annealing using spectroscopicellipsometry. Four distinct processes are identified during a thermal annealing process: (I) theevaporation of residual solvent above the glass transition temperature of the blend, (II) therelaxation of non-equilibrium molecular conformation formed through spin-casting, (III) thecrystallization of both P3HT and PCBM components and (IV) the phase separation of the P3HT andPCBM domains. These effects can not be simultaneously resolved using other techniques. Torelate such processes to device operation, a series of photovoltaic devices were fabricated toassess the effect of the annealing treatments explored in this work. Devices annealed at 150 oCfor between 10 and 60 mins exhibit an average power conversion efficiency of around 4.0%. Wedemonstrate that the rate at which a thermally annealed P3HT:PCBM film is returned to roomtemperature directly affects the efficiency of an OPV device. We find that the rapid quenching of afilm from the annealing temperature to room temperature hampers the crystallization of theP3HT and can trap non-equilibrium morphological states, which impacts on device short circuitcurrent, fill factor and thus operational efficiency. This study provides a direct insight andfundamental understanding of the dynamic nanoscale morphology evolution in photovoltaic blendfilms during their initial formation and post-treatment stages; an advance that we believe offersthe prospect of guiding the self-assembly and optimization of thin film-structure for highperformance OPV device applications. Ref: 1. The development of nanoscale morphology inpolymer:fullerene photovoltaic blends during solvent casting. Tao Wang, Alan D F Dunbar, Paul AStaniec, Andrew J Pearson, Paul E Hopkison, J Emyr Macdonald, Samuele Lilliu, Claire Pizzey,Nicholas J Terrill, Athene M Donald, Anthony J Ryan, Richard A L Jones, David G. Lidzey. SoftMatter, 6: 4128-4134 (2010) 2. Evolution of structure, optoelectronic properties and deviceperformance of polythiophene: fullerene solar cells during thermal annealing. Tao Wang, AndrewJ Pearson, David G Lidzey, Richard A L Jones. Adv. Funct. Mater. DOI: 10.1002/adfm.201002300(2011)

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16:30 The formation of a thin film phase: the polymorphism of dihexyl-terthiopheneAuthors : B. Wedl (1) R. Resel (1) G. Leising (1) B. Kunert (1) I. Salzmann (2) O. Werzer (3) G.Gabone (4) Y. Geerts (4) M. Sferrazza (5) (1) Institute of Solid State Physics, Graz University ofTechnology, Petersgasse 16, A-8010 Graz, Austria (2) Institut für Physik, Humboldt-Universität zuBerlin, Newtonstraße 15, D-12489 Berlin, Germany (3) Centre for Organic Electronics, TheUniversity of Newcastle, Callaghan, NSW 2308, Australia (4) Chimie des Polymères, UniversitéLibre de Bruxelles, Campus de la Plaine CP 206/0, 1050 Bruxelle, Belgium (5) Département dePhysique, Université Libre de Bruxelles, Boulevard du Triomphe, CP 223, Bâtiment NO, B-1050Bruxelles, BelgiumResume : The formation of polymorphic crystal structures of the organic semiconductor dihexyl-terthiophene (C6TTC6) is investigated in single crystals and thin films prepared by differentpreparation methods. On the one hand, films are prepared by solution processing methods likespin-coating, dip-coating and drop-casting, and, on the other hand, by physical vapourdeposition. Various x-ray diffraction methods to determine crystallographic structure arecombined with morphological investigations by atomic force and optical microscopy, whichprovide information on the structural and morphological development of the films starting frommonolayer coverage. Three different polymorphic crystal structures are identified and theirappearance is related to the thin-film preparation parameters. A full structure solution of thesingle-crystal polymorph is provided and the unit cell parameters of a polymorph present in thinfilms only are determined by grazing-incidence x-ray diffraction. The crystallisation speed isvaried by the evaporation rate of the solvent and is identified as key parameter for the respectivepolymorphs present in the films. Slow crystallisation induces preferential growth in the bulkstructure, while fast crystallisation leads to the occurrence of the thin film polymorph.Furthermore, by combining x-ray reflectivity investigations with photoelectron spectroscopyexperiments the presence of a lying wetting layer of C6TTC6 on SiOx below the standingmolecules phase of the thin film phase could be evidenced. Our work clearly shows that ratherthe crystallisation dynamics that the film thickness governs the occurrence of a thin film phase oforganic semiconductor thin films.

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16:30 Structural Model of Regioregular Poly(3-hexylthiophene) Obtained by Electron Diffraction AnalysisAuthors : N. Kayunkid, S. Uttiya and M. Brinkmann Institut Charles Sadron, CNRS-Universit?eStrasbourg, 23 rue du Loess, 67034 Strasbourg, FranceResume : This study presents a structural analysis of regioregular poly(3-hexylthiophene)(P3HT) based on electron diffraction from epitaxied thin films. Epitaxial orientation of the hexanefraction of P3HT was performed by slow rate directional solidification in 1,3,5-trichlorobenzeneleading to highly oriented and crystalline P3HT films with different contact planes (1,2).Representative electron diffraction patterns corresponding to different zone axes were obtainedby the rotation-tilt electron diffraction method. A trial-and-error method based on molecularmodeling and calculation of the electron diffraction patterns for the different zone axes was usedto determine the crystal structure of P3HT. The unit cell is monoclinic with space group P21/c andtwo chains per cell (a = 1.60 nm, b = 0.78 nm, c = 0.78 nm and γ = 86.5 deg). The stackingperiod of successive polythiophene backbones along the b axis is 0.39 nm but short interplanardistances of 0.34 nm are observed because the conjugated polythiophene backbones are tilted tothe b axis. The n-hexyl side groups crystallize in an orthogonal subcell with parameters as = 0.7nm and bs = 0.78 nm. The present structural model highlights the essential role of the linear sidechain crystallization on the supra-macromolecular packing of “hairy-rod” polymers like P3HT. (1)Brinkmann, et al. Adv. Mater. 2006, 18, 860. (2) Brinkmann, et al. Adv. Funct. Mater., 2007, 17,101. (3) N. Kayunkid et al. Macromolecules, 2010, 43, 4961.

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16:30 Highly oriented and nanotextured films of regioregular poly(3-hexylthiophene) grown by epitaxyon the nanostructured surface of an aromatic substrateAuthors : Martin Brinkmann (1), Christophe Contal (1), Navaphun Kayunkid (1), Tatjana Djuric(2), Roland Resel (2) (1) Institut Charles Sadron, CNRS- University of Strasbourg, 23 rue duloess, 67034 Strasbourg, France. (2) Institute of Solid State Physics, Petersgasse 16, 8010 Graz,Austria,Resume : A simple method for the nanotexturing and orientation of regioregular poly(3-hexylthiophene) (P3HT) thin films has been developped. Epitaxial growth of P3HT on the surfaceof an aromatic salt (potassium 4-bromobenzoate) leads to highly oriented and nanotexturedP3HT films which consist of a regular network of interconnected semi-crystalline domainsoriented along two preferential in-plane directions. The overall crystallinity and the level ofin-plane orientation of the P3HT films are controlled by the temperature of isothermalcrystallization (Tiso). Well defined electron diffraction patterns with sharp reflections obtained forTiso=180°C indicate that the crystalline domains grow with a unique (1 0 0) P3HT contact planeon the K-BrBz substrate with the P3HT chains oriented along the [0 ±2 1] K-BrBz directions of thesubstrate. During the annealing of the polymer film, the surface of the aromatic salt undergoes atopographic reconstruction resulting in a regular nanostructured “hill and valley“ topography thattemplates and orients the growth of P3HT. Preferred orientation of P3HT crystalline domainsoccurs at step edges of the substrate and is favored by the matching between the layer period ofP3HT and the terrace height of the K-BrBz substrate.

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16:30 Investigation of the morphology of Au/Polystyrene and Au/Poly(methyl methacrylate)nanocomposites synthesized by radio-frequency sputteringAuthors : F. Ruffino, M. G. Grimaldi Dipartimento di Fisica e Astronomia, Università di Catania viaS. Sofia 64, I-95123 Catania, Italy CNR-IMM MATIS, via S. Sofia 64, I-95123 Catania, Italy V.Torrisi, G. Marletta Laboratory for Molecular Surface and Nanotechnology (LAMSUN), Departmentof Chemical Sciences- University of Catania and CSGI, Viale A. Doria 6, I-95125, CataniaResume : Materials fabricated by metal clusters and thin metal films on polymeric substrateshave emerged in the development of organic electronics. A key point is the interaction at themetal-polymer interface since the electrical behaviour are influenced by the interface structure.Fundamental importance acquires the growth kinetics of the metal on the polymer surface andhow the polymer influences the film morphology. This work reports on the atomic forcemicroscopy study of the morphology evolution of Au film sputtered on two polymeric substrates:Poly(methyl methacrylate) (PMMA) and Polystyrene (PS). The Au islands evolve with increasingthe deposition time t, from droplet-like islands, to a partially coalesced worm-like islands, topercolation, and finally to a continuous film. Applying opportune growth models, severalparameters were obtained: 1) the critical radii for the partial coalescence, 8.7 and 7.6 nm for Auon PS and PMMA, respectively; 2) the room-temperature Au surface diffusion coefficient,3.2x10e-17 and 1.9x10e-17 m2/s for Au on PS and PMMA, respectively; 3) the critical coverage61 and 56% at which the percolation occurs for Au on PS and PMMA, respectively; 4) the scaling,growth and roughness exponents 3.8, 0.28, 1.06 for Au on PS and 4.3, 0.23, 1.03 for Au onPMMA. Knowing these parameters, t can be tuned so to control the film nanostructure. A generalmodel is proposed for the influence of the polymers on the aggregation of metal nanoclusters.

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16:30 Determination of the energy structure of the sandwich-type organic thin filmsAuthors : I.Muzikante, J. Indrikova, J. Latvels, K. Pudzs, M. Rutkis Institute of Solid State PhysicsUniversity of Latvia, Kengaraga Str. 8, Riga LV 1063, LatviaResume : The fundamental part to design effective sandwich type organic films, i.e.,electrode/organic layer(s)/electrode is knowledge of energetic parameters of materials. Anionization potential, and energy gap directly affect such important electronic processes as chargecarrier generation and transport. These parameters are useful to create the energy diagram bothof a material and structure electrode/organic layer/electrode. In order to have complete energydiagram of thin film structure the values of the work functions of electrodes are necessary aswell. In order to characterises energy gap several parameters are applied such as an opticalenergy gap, an adiabatic energy gap, a transport gap, a threshold of intrinsic conductivity. Thevalue of the optical energy gap is usually measured as the energy, where the normalizedabsorption and fluorescence spectra intersect or from electromodulated absorption spectra.Besides the difference between the oxidation and reduction potentials corresponds to the energygap. In order to determine the adiabatic energy gap, one must measure the charge carrierenergies after their vibronic relaxation to the molecular polaron states. In this work we presentone of the methods to determine the threshold of intrinsic conductivity in low molecular organicthin films. It is the dependence of quantum efficiency of intrinsic photoconductivity. The value oftransport band is applied as difference between the values of the HOMO and LUMO a material. Inthis work the values of the HOMO and LUMO levels are calculated according to the RHF ab initiocalculations with basis set 6-31G** by Gaussian G09W software package. Kelvin probe techniqueis applied to determine the values of the ionization potential of the organic layer and the values ofthe work function of the electrodes. In this work the values of the energy gaps, local trappingstates and ionization potentials of the thin films of indandione and carbazole derivatives andcombined system was determined by the methods mentioned above. The intercorrelation of allparameters characterisizing the energy gap will be presented. According to these results theenergy diagrams of thin films of indadione and carbazole derivatives with Au, Al, Ni, Cu and ITOelectrodes will be presented.

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16:30 Theoretical study of interaction between bathocuproine and various types of metalsAuthors : M.D.Bhatt, T.Sakurai, S.Suzuki,1 and K.Akimoto, Institute of Applied Physics, Universityof Tsukuba, Japan. 1 Institute of Materials Science, University of Tsukuba, Japan.Resume : An interaction at organic/metal interfaces influences their energy level alignment andcarrier injection probability, hence it affects the performance of organic semiconductor devices.The origin of the interfacial interaction has been widely discussed recently; however, themechanism is still unclear. In this study, the interactions between bathocuproine (BCP) andvarious types of metals (Ca, Mg, Ag, Cu, Au) have been investigated using density functionaltheory (DFT) calculations. The binding energy decreases gradually with increasing metal workfunction. The transferred charge decreases gradually with increasing metal work function similarto the binding energy. The transferred charge is proportional to the Coulomb interaction and theequilibrium distances between BCP and metal surfaces are roughly the same. Therefore,contribution of ionic interaction in the binding energy between BCP and metal seems to be large.The orbital mixing becomes significant, especially in the Fermi level of metals and LUMO of BCP.The mixing of carbon atomic orbitals into the Fermi level increased with decreasing metal workfunction. When we consider the electron transport between BCP and metal electrode, we shouldremark the continuity of the wave function at the interface. Therefore, this overlapping of thewave function may be one of the reasons for the improvement of the carrier transport propertiesat the interface between BCP and metals [1]. [1] T.Sakurai et al., JAP 107, 043707 (2010).

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16:30 Studying polymer and fullerene intermixing in laterally patterned structures with soft x-rayspectromicroscopyAuthors : Xiaoxi He and Chris McNeillResume : Polymer/fullerene bulk heterojunction solar cells are prepared by depositing a blend ofpolymer and fullerene from a common solution and annealing to optimize device performance.The “ideal” morphology is thought to consist of phase-separated pure domains with domain sizecomparable to the exciton diffusion length. However recently it has been shown[1] that fullerenederivatives such as PCBM are miscible in conjugated polymers commonly used in organic solarcells and that pure phases may not be thermodynamically accessible in some cases. Here wereport on the use of Scanning Transmission X-ray Microscopy (STXM) to study polymer andfullerene intermixing in laterally patterned films. Intermixing is studied by patterning thin films ofPCBM into 20 µm stripes on silicon nitride membranes via photo-lithography and laminatingconjugated polymer films on top. These samples are then annealed overnight to achieve thermalequilibrium and the resulting blend composition measured with STXM. Our results show thatsignificant intermixing of PCBM and polymer can result from initially pure films providingchallenges for the engineering of so-called ideal architectures. [1] Collins et al, “MolecularMiscibility of Polymer-Fullerene Blends”, J. Phys. Chem. Lett. 1(21) 3160-3166 (2010).

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16:30 Comparison between the density-of-states of picene TFTs measured in vacuum and exposed toairAuthors : J. Puigdollers. Dept Eng Electronica and Center Research of Nanoengineering.Universitat Politecnica Catalunya C. Moreno. Center Research of Nanoengineering (CrNE).Universitat Politecnica Catalunya A. Marsal. Dept Eng Electronica. Universitat PolitecnicaCatalunya C. Voz. Dept Eng Electronica. Universitat Politecnica Catalunya R. Alcubilla Dept EngElectronica and Center Research of Nanoengineering. Universitat PolitecnicaResume : Picene has recently attracted much attention as the active layer in thin-film transistors(TFTs) because of its good performance in air and significant oxygen sensing effect [1]. In thiswork, we have fabricated picene TFTs that exhibit hole field-effect mobilities up to 1.2 cm2/V.sand on/off ratios above 10^5 in ambient conditions. These devices have been electricallycharacterised over the temperature range 300 – 360 K in air and also under vacuum conditions.In particular, the activation energy (Ea) of the channel conductivity as a function of the gate bias(Vgs) has been measured. The dependence of Ea on Vgs corresponds to a gradual shift of theFermi energy towards the valence band as more trap states are filled by holes injected from theelectrodes. Following a procedure described elsewhere [2], the density of localized states can beestimated from the derivative of the activation energy with respect to gate bias. Then, thecalculated density of states is compared for devices measured in air and under vacuum. Theseresults can help to understand the oxygen sensing capabilities of picene devices, together withtheir enhanced electrical performance after air exposure. [1] Y. Kaji et al., Appl. Phys. Lett. 95,183302 (2009); doi:10.1063/1.3257373 [2] J. Puigdollers et al., Organic Electronics 11, 1333(2010); doi:10.1016/j.orgel.2010.05.007

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16:30 Bilayer polymer/oxide coating for electroluminescent organic semiconductorsAuthors : Luciana Tavares1, Jakob Kjelstrup-Hansen1, Horst-Gunter Rubahn1, and Heinz Sturm21University of Southern Denmark, NanoSyd, Mads Clausen Institute, Alsion 2, DK-6400Sonderborg, Denmark; 2BAM – Div. Scanning Probe Microscopy, Tribology and Wear Protection,Unter den Eichen 44-46, D-12205 Berlin, and TU Berlin, IWF , Pascalstr. 8-9, D-10587 Berlin,GermanyResume : Organic materials have been given much attention due to their intriguing propertiesthat can be tailored via synthetic chemistry for specific applications combined with their low priceand fairly straight-forward large-scale synthesis. Para-hexaphenylene (p6P) nanofibers emitpolarized light with a highly anisotropic emission profile, act a sub-wavelength opticalwaveguides, and form the basis for a new type of miniature OLEDs. However, p6P moleculessuffer reduction of luminescence intensity during photoexcitation under UV light. Suchphotoreaction is understood as a consequence of the interaction of the fibers with oxygen. Wehave developed a bilayer coating that does not change significantly the p6P spectrum but strongly

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reduces bleaching. This bilayer coating consists of a first layer of a stable polymer (PMMA) on topof the organic nanofibers as a protecting layer for avoiding modifications of the p6P luminescencespectrum and as a second layer SiOx for blocking the oxygen penetration. In this work, we showthe applicability of this bilayer coating of PMMA/SiOx in prolonging the operational lifetime offield-effect transistor (FET) devices based on p6P nanofibers. The coating prevents strongdegradation of transferred nanofibers on FET platforms during electrical biasing as is observed foruncoated devices. We are currently investigating the effect of the coating during electricallystimulated light emission experiments from transferred fibers on transistor platforms.

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16:30 Structure determination of organic thin films with pair distribution function techniqueAuthors : Chris Elschner Alexandr A. Levin Moritz Riede Karl LeoResume : Organic semiconducting materials allow new optoelectronic devices combining theexcellent optical properties of organic dyes with semiconductor behavior. Organic Light EmittingDiodes (OLED) and Organic Solar Cells (OSC) are successful examples in this field. Organicdevices contain several layers with different molecules and often show an amorphousmorphology, especially in the case of mixed layers with more than one type of molecule perlayer. The electrooptical properties of such a device crucially depend on the morphology at asub-nm scale. Molecules show a strongly anisotropic behavior in the transport and in the opticalproperties. A way to get information about the short range order of amorphous as well ascrystalline systems is the pair distribution function (PDF) technique derived from X-ray diffraction(XRD) measurements. We produced Fullerene C60 thin film samples via vacuum deposition onglass substrates and measured the X-ray diffraction pattern under grazing incidence condition.The PDF of the organic layer can be calculated and being compared to powder measurements.We show that it is possible to extract structural parameter of the thin film direct from the x-raydata without any single crystal x-ray data; at least for a good-natured material like C60.

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16:30 The influence of molecular design of diindenoperylene derivatives on thin film morphology andperformance of organic solar cellsAuthors : Christoph Schuenemann, Joerg Alex, Jan Meiss, Wolfgang Tress, Annette Petrich, KarlLeo, and Moritz Riede Institute for Applied Photophysics, TU Dresden, GermanyResume : Diindenoperylene (DIP) is a well known organic semiconductor which is also anattractive absorber material for small molecule organic solar cells. We have synthesized Ph4-DIP,a novel DIP derivative, consisting of the DIP core and four phenyl rings attached to the twoindeno-groups. To compare these two similar molecules, DIP and Ph4-DIP, we characterize themorphology of thermally evaporated thin films using x-ray diffraction and atomic forcemicroscopy. Pristine films and mixed layers with C60 (1:1 by volume) are deposited at differentsubstrate temperatures. Whereas DIP forms highly crystalline pristine and blend layers even onunheated substrates, Ph4-DIP is found to grow amorphous even at elevated substratetemperatures of 110°C in both pristine and blend layers. These results show the strong influenceof the molecular design on the molecular arrangement in organic thin films. The stacking of thePh4-DIP molecules is disturbed by the four phenyl rings that are tilted with respect to the flat DIPcore. DIP molecules, i.e. without these phenyl rings, however, are able to stack very densely andform large crystallites. These morphological results can explain the differences in exciton diffusionlength and charge carrier mobilities we determine for solar cells of both materials.

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16:30 GROWTH AND CHARACTERIZATION OF PARA-HEXAPHENYLENE NANOFIBRES USING HOT WALLEPITAXYAuthors : K. Rehman (a), C. Simbrunner(a), G. Schwabegger(a), R. Ahmed(a) and H. Sitter(a)(a) Inst. of Semiconductors and Solid State Physics, Johannes Kepler University Linz, Austria.Resume : We have investigated the size and shape of para-hexaphenylene (PHP) nanofibresgrown on muscovite mica (001) by hot wall epitaxy at varying substrate temperatures andgrowth times. The discontinuous thin films were investigated by atomic force microscopy and thedependence of needle length, height and width on substrate surface temperature and growthtime was evaluated. We have observed that the length of the needles is more significantlyinfluenced by the growth temperature than by the growth time. The substrate temperaturedependence of the length, height and width of the nanofibres allows to evaluate activationenergies for the growth in these three directions. The epitaxial growth of self assembled fibres onmica substrates is compared with the deposition on amorphous surfaces like SiO2. Since there isno epitaxial relationship between substrate and PHP molecules, the layers consist of standingmolecules, in contrast to the nanofibres in which the molecules were laying flat on the substrate.As a consequence the layers grown on SiO2 show a much lower degree of crystallographic order.The effect of external parameters, like an electric field, applied during the deposition, wasstudied in detail. The influence on the crystallographic order and the surface morphology will bediscussed.

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16:30 Interplay between solid-state organization and optical properties of thin films of poly-arylene-vinylene and -difluorinated vinylene:fullerene blends for photovoltaicsAuthors : Elena Dilonardo 1,2, Antonio Cardone 3, Maria M. Giangregorio 2, Maria Losurdo 2, PioCapezzuto 1, Gianluca M. Farinola 1, Francesco Babudri 1 Francesco Naso,1 Giovanni Bruno2 1Dipartimento di Chimica, Università degli studi di Bari “Aldo Moro”,Via E. Orabona 4, 70126 Bari,Italy. 2 Istituto di Metodologie Inorganiche e Plasmi, IMIP-CNR, Via E. Orabona 4, 70126 Bari,Italy. 3 Istituto di Chimica dei Composti Organometallici, ICCOM-CNR di Bari, Via E. Orabona 4,70126 Bari, Italy.Resume : Today considerable efforts have been devoted to the synthesis of low band-gapconjugated polymers for application in organic polymer solar cells because of the improved

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absorption of the solar photon flux. Many low band-gap polymers are prepared by alternatingcopolymerization of electron-donating donor and electron-withdrawing acceptor units. Theinteraction between these two units can reduce the polymer band-gap, increasing the sunlightabsorption. Benzothiadiazole is commonly used as acceptor block unit in low band-gap polymers.In this contribution we investigate the interplay between the supramolecular organization andoptical properties of thin films of conjugated polymers consisting of benzothiadiazole andthiophene with electron-withdrawing difluorovinylene, and electron-donating vinylenesubstituents. The interplay is elucidated exploiting atomic force microscopy, spectroscopicellipsometry and photoluminescence to obtain complementary information. F-atoms in vinyleneunit yield to a blue shift of the absorption peaks of 0.2 eV respect the hydrogenated polymer; it isascribed to the preventing of polymer π-stacking by fluorine atoms on the vinylene unit. Theabsorption coefficient of fluorinated polymers is an order of magnitude higher then thehydrogenated one, which indicates its application as promising photovoltaic material. Theproperties of the polymer as donor blended with fullerene as an acceptor are investigated andcorrelated to the photovoltaic performances.

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16:30 Implementation of a white-beam x-ray reflectivity setup at the LNLS and application toself-assembled organic layersAuthors : M. de Pauli, A. Malachias, C. A. Perez Laboratorio Nacional de Luz Sincrotron, CEP13083-970, C.P. 6192, Campinas, Brazil.Resume : In this work we introduce the use of white-beam diffraction at the BrazilianSynchrotron Light Laboratory (LNLS - Campinas, Brazil) to explore ordering and thermodynamicproperties of organic layers. The setup is based on a bending magnet beamline, using a fastSi-drift detector for energy discrimination. A dedicated chamber was built to handle samplesunder controlled atmosphere, allowing for heating and cooling in the range from (4°C - 300°C).Results obtained in self-organized phosphonic acids will be discussed as a general example to theapplications of the technique. In such case, phase transitions within the lamellar phase, as well asorder-disorder transitions are observed. Energy dispersive results are compared withconventional angular-resolved diffraction technique, evidencing the advantages and limitations ofthis method. The technique can be applied to obtain real-time measurements in organic layeredsystems such as polymers and colloids.

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16:30 6T on silver: the influence of the surface miscutAuthors : Thorsten Wagner, Daniel Roman Fritz, Peter Zeppenfeld Institute of ExperimentalPhysics, Johannes Kepler University Linz, AustriaResume : The growth of alpha-sexithiophene (6T) on Ag(110) and Ag(441) was studied bymeans of scanning tunneling microscopy (STM) and photoelectron emission microscopy (PEEM).In contrast to (110) surfaces of other metals, 6T molecules deposited on Ag(110) do not alignexclusively along the close-packed atomic rows but also perpendicular to them. The mixture ofmolecules arranged with their long axis parallel to the [001] and [1-10] directions lead to astrained checkerboard pattern. Besides the checkerboard phase, a well ordered homochiral phasewas found. STM images show that the molecules in the second layer are exclusively aligned in the[001] direction but their arrangement is strongly influenced by the checkerboard phase of thefirst layer. On the vicinal Ag(441) surface, the molecules of the first layer align exclusively alongthe [1-10] direction, i.e. parallel to the steps of the substrate. In addition, step bunching andfaceting of the vicinal substrate surface was found upon adsorption of 6T. For more than twomonolayers of 6T deposited on both, the Ag(110) and the Ag(441) surface, a 3D growth wasobserved. The PEEM intensity curves recorded during film growth mode provide additional detailson the complex growth of the molecules on both surfaces.

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16:30 Probing individual crystallites by imaging photoelectron spectroscopyAuthors : Thorsten Wagner, Daniel Roman Fritz, Peter Zeppenfeld Institute of ExperimentalPhysics, Johannes Kepler University Linz, AustriaResume : The growth of alpha-sexithiophene (6T) depends strongly on the quality of thesubstrate surface: If the surface is clean and well ordered, the molecules are lying flat on thesurface and form characteristic needles. If the surface is disordered or at certain defects, theygrow in an upright standing manner forming platelet like crystallites. We have appliedphotoelectron emission microscopy (PEEM) to study in real-time the growth of 6T film on Ag(110)at different sample temperatures. The use of different light sources (Hg, D2 and He lamps) allowsto probe the samples over a wide range of excitation energies from 4.9 to 21.2 eV. In particular,high energy light sources are suitable to excite photoelectrons not only from the substrate but toovercome the ionization potential of the semiconducting organic thin film itself. Besides thereal-time characterization of the morphology PEEM can provide local spectroscopic information ona sub-µm scale. An imaging energy filter allows to probe the electronic structure of individualcrystallites of 6T on Ag(110). Both types of crystallites, needles and platelets, can not only bedistinguished by their shape but also by their photoelectron emission spectra. We also identify awetting layer consisting of lying flat molecules which has essentially the same spectroscopicsignature as the molecules in the needles.

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16:30 Energy filtered electron microscopy spectrum imaging of nanoscale phase separation in organicheterojunctionsAuthors : Wolfram Schindler, Markus Wollgarten, Konstantinos Fostiropoulos. Helmholtz-ZentrumBerlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, 14109 Berlin, GermanyResume : Detailed imaging of the morphology of the bulk heterojunction (BHJ) in organic solarcells is essential since it greatly impacts the device performance. The challenge is to fabricate

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well-entangled crystalline donor-acceptor networks at the nanometer scale to efficiently transportboth excitons and charge carriers. We applied energy filtered transmission electron microscopyspectrum imaging (EFTEM SI) to characterize the phase separation in organic BHJs at thenanoscale. The different carbonaceous species can be distinguished by their bulk plasmonenergies [1]. We prepared a reference series of 40 nm thick blend layers by co-evaporation ofzinc phthalocyanine (ZnPc) and C60 with various mixing ratios and recorded their electronenergy-loss spectra. With increasing C60 concentration the plasmon position shifted continuouslyfrom the peak at 23 eV energy-loss of pure ZnPc to that of pure C60 at 26 eV. This spectralcontrast was used to map the local phase separation in a ZnPc:C60 blend induced by elevatedsubstrate temperature during deposition. While on the conventional TEM micrograph only suitablyoriented crystalline C60 domains were identified by their characteristic lattice fringes [2], therespective plasmon map allowed to analyze the complete lateral phase distribution independentlyof the domains’ crystallinity or their crystal orientation. [1] M.H. Gass. et al., Nano Lett. 2006, 6,376-379. [2] K. Fostiropoulos, W. Schindler, phys stat sol (b) 2009, 246, 2840-2843.

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16:30 Donor-block-acceptor systems for photovoltaic applicationsAuthors : Sven Huettner (1), Michael Sommer (2), Kerr Johnson (1), Ya-Shih Huang (1), RichardH. Friend (1) 1) Cavendish Laboratory, University of Cambridge, UK 2) Melville Laboratory,Universtiy of Cambridge, UKResume : Polymer solar cells rely on a donor and an acceptor material that form aninterpenetrating morphology. This ensures charge separation at the interface, but also a propercharge percolation to the electrodes at the same time. Furthermore, the right position of HOMOand LUMO levels of the respective materials are important for an efficient charge separation. Wepresent novel donor-block-acceptor polymers that can be applied in light harvesting devices. Wewant to control the heterojunction interface by these donor-block-acceptor molecules. These actas a phase compatibilizer to modify the polymer blend phase separation, but also affect theenergetic environment of the heterojunction. Besides their structural characterisation, weinvestigated these materials by time-resolved spectroscopy. The donor-block-acceptormacromolecules contain P3HT as a donor block, whereas the acceptor block consists of perylenebisimide derivatives or F8TBT.

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16:30 Molecular Depth Profiling of OLEDs with Ar cluster ion beamsAuthors : Jiro Matsuo, Kazuya Ichiki, Yamamoto, Takaaki Aoki and Toshio Seki Quantum Scienceand Engineering Center, Kyoto University, Gokasho, Uji, 611-0011, JAPANemail:[email protected] : Much attention is paid to studying multilayer structures of organic semiconductordevices. However, organic semiconductor molecules are very fragile and are difficult to analyzewith conventional techniques because their molecular structure is seriously damaged by probebeams. A novel technique to realize molecular depth profiling of organic materials has beendeveloped by using large Ar cluster ion beams, which can sputter materials with less residualdamage because of the low-energy effect and high sputtering yield. Secondary molecular ions areutilized to reveal the structure during the sputtering of organic materials. We have demonstratedmolecular depth profiles of Alq3 and NPD multilayers deposited on substrates (NPD/Alq3/ITO/glass) with 5.5 keV Ar cluster ions before and after annealing at 100, 120 and 150 C. Themultilayer structure was clearly revealed by using Ar cluster ion. For the sample annealed at 100C, no diffusion of either Alq3 or NPD molecules was observed. However, after annealing at 120 C,diffusion of Alq3 molecules into the NPD layer could be observed but without diffusion of NPDmolecules. Finally, after annealing at 150 C, the depth profiles of Alq3 and NPD moleculeschanged dramatically, and the two molecules diffused into each other. These results indicate thatmolecular depth profiling of multilayer structures with Ar cluster ions provides useful informationof organic molecules in OLED devices. This work is partially supported by JST, CREST. [1] S.Ninomiya, K. Ichiki, H. Yamada, Y. Nakata, T. Seki, T. Aoki and J. Matsuo, Rapid Comm. in MassSpec., 23, pp. 3264-3268 (2009)

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16:30 Influence of ITO surface treatment on growth and efficiency of chloroaluminum phthalocyaninebased solar cellsAuthors : Bregt Verreet†‡, Robert Müller†, Barry P. Rand†, Karolien Vasseur†‡ and PaulHeremans†‡ † imec, Kapeldreef 75, B-3001 Leuven (Belgium) E-mail: [email protected] ‡ESAT,Katholieke Universiteit Leuven, Kasteelpark Arenberg 10, B-3001 Leuven (Belgium)Resume : Until recently, the impact of growth conditions and substrate preparation on organicsolar cell device performance has received relatively little attention. Here, we treat indium tinoxide with different materials, such as CuI, perylene-3,4,9,10-tetracarboxylic dianhydride,molybdenum oxide (MoOx) and 5 different trichlorosilane based self-assembled monolayers. Ontop of these surfaces, chloroaluminum phthalocyanine (ClAlPc) films are grown at substratetemperature of 105ºC, and characterized via absorption, AFM, and XRD measurements.Absorption measurements reveal that substrate surface treatment has a large impact on theabsorption of the grown ClAlPc-film, with peak absorption shifting from λ=770 nm towards λ=816nm. XRD reveals ClAlPc molecules to lie flat when grown on MoOx, while they stand up on silanemonolayers. Organic bilayer cells using these films as donor layers and C60 as acceptor werefabricated. The solar cell grown on the MoOx anode reaches a power conversion efficiencyη=2.27%, with open-circuit voltage Voc=0.73 V and short-circuit current Jsc=5.04 mA/cm2. Withsilane treated substrates, the current increases to values around Jsc=9 mA/cm2, while Voc dropsto ~0.55 V, leading to efficiencies of up to 3.3%. These drastic changes of solar cell parameterswill be discussed by taking into account temperature dependent measurements and sensitivephotocurrent spectra. Financial support of EC project ONE-P (FP7-212311) is acknowledged.

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16:30 Investigation of Fermi Level Alignment at Metal/Organic Semiconductor InterfacesAuthors : Nyun Jong Lee1, Yu Jeong Bae1, Tae Hee Kim1*, Hyunduck Cho2, Changhee Lee2, andEisuke Ito3 1 Department of Physics, Ewha Womans University, Seoul, South Korea 2 School ofElectrical Engineering and Computer Science, Seoul National University, Seoul, South Korea 3Flucto-Order Functions Research Team, RIKEN Advanced Science Institute, Wako, Saitama351-0198, JapanResume : Due to the promising applications in optoelectronics and spintronics, organicsemiconductors(OSCs) have attracted tremendous attention for over a decade. The injection ofspin-polarized carriers could be used to control the light emitted by organic light emitting diodes.Thus, the multi-functionality using photons to control spin current and vice versa would beachievable with OSCs. Before realistic applications can be achieved, however, more systematicwork is needed to understand the mechanism of spin injection and transport. To understand thebasic structural and electrical properties at metal/organic interfaces is of great significance. Weinvestigated the interfacial properties of a hetero structure consisting of a highly-qualifiedinterface between Cu-phthalocyanine (CuPc) and transition metals, such as Co and Fe. Wefocused on understanding interface electronic states and energy alignment by XPS and UPSexperiments. The experimental determination of binding energies of the highest occupiedmolecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) states of organiclayers with respect to the Fermi level (EF) of the electrode was carried out. Based on thesevalues, the energy barriers for hole and electron injection from the metal to organic layer can beestimated. Our results show that the EF of CuPc shifts strongly depending on the metal electrode;the bigger shift of the EF observed when a nominal 1.8nm thick MgO layer is inserted betweenFe(100) and CuPc layers. Different EFs were also observed for an epitaxial Fe(100) and a polycrystal Fe.

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16:30 The electronic structure of alkali metal doped molecular thin films: a photoemission studyAuthors : E. Reinisch1, G. Koller1, P. Puschnig2, M. Ostler3, T. Ules1, S. Berkebile1,C. Ambrosch-Draxl, T. Seyller3, M.G. Ramsey1 1 Institute of Physics, University of Graz, A-8010 Graz, Austria2 Atomistic Modelling and Design of Materials, University of Leoben, 8700 Leoben, Austria. 3Technische Physik, University Erlangen Nurnberg, D-91058 Erlangen, GermanyResume : Upon alkali metal doping of organic semiconducting molecules gap states, polaronsand bipolarons, are induced. For a detailed momentum resolved electronic band structuredetermination highly ordered films and monolayers are required. Here we followed the electronicprocesses occurring upon alkali metal doping of a highly ordered sexiphenyl monolayer onCu(110) for increasing amounts of Cesium. We have determined the electronic band structureand in addition two-dimensional momentum maps have been recorded for the molecular frontierorbitals. For a 6P monolayer on Cu(110) the LUMO has become occupied due to hybridization. Afirst Cs dose causes a large drop in the work function and a concomitant downwards shift inenergy of all molecular orbitals and the hybridization with Cu is lifted. Increasing the amounts ofCs causes a bipolaron state to appear, due to a charge transfer from the alkali metal to the 6Pmolecule. A further increase in Cs leads to the formation of interacting bipolarons. This has beenfollowed with angle resolved photoemission and complete 2D momentum maps of the induceddoping states. Supported by the Austrian Science Funds FWF (P21330-N20). We acknowledge theHZB Berlin - BESSY II for provision of synchrotron radiation at beamline TGM 4 and funding fromthe European Community's Prog. (FP7/2007-2013) grant n.°226716.

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16:30 In-depth analysis of polymer/fullerene blend films using Spectroscopic EllipsometryAuthors : Sebastian Engmann,Vida Turkovic, Harald Hoppe, and Gerhard Gobsch TechnischeUniversitaet Ilmenau, Fakultaet fuer Mathematik und Naturwissenschaften, Institut fuer Physik,Experimentalphysik I, Weimarer Strasse 32, 98693 Ilmenau, GermanyResume : The validity of various optical models in relation to the blending ratio ofpolymer/fullerene blends used in organic photovoltaics has been tested. Fullerene inclusionsshape and the degree of polymer crystallinity inside the film have been investigated usingSpectroscopic Ellipsometry. Our measurements indicate a percolation threshold at around 40wt%PCBM. In the case of lower PCBM contents, fullerene inclusions in the P3HT matrix have been ofisotropic shape, while above the percolation limit, rods were formed. The influence of PCBMcontent in the film on the P3HT crystallinity is discussed.

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16:30 Preparation and SPM-based Characterisation of Thin Films of OligoanilinesAuthors : Benjamin P Brown1,2, Charl FJ Faul2, Mervyn Miles3 and Loren Picco3 1 Bristol Centrefor Functional Nanomaterials, University of Bristol, Bristol, BS8 1FD 2 School of Chemistry,University of Bristol, Bristol, BS8 1TS 3 H. H. Wills Physics Laboratory, University of Bristol,Bristol, BS8 1TLResume : Oligomers of the conducting polymer polyaniline (‘oligoanilines’) retain its redox- andpH-switchable insulating and conducting states while offering a substantial improvement inprocessibility and tunability of the structure, molecular architecture and optoelectronic properties[1]. For example, oligoanilines doped with surfactant acids form organised structures with strongconductivity-order dependence [2]. However, a greater understanding of the structure-functionrelationship is needed to facilitate the use of these materials in electronic devices. In this work,thin (<10nm) films of various oligoanilines have been prepared using drop casting and spincoating techniques. AFM and STM have been used to characterise the physical and electronicproperties of the films formed, and bulk and in situ-AFM electrochemical studies have been usedto characterise the electrochemical properties. The stability of the films during imaging with thehigh-speed atomic force microscope (HSAFM) [3] has also been examined with the intention of

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using established tip biasing techniques [4] to induce localised redox reactions, enabling the userto define the extent and shape of the conductive regions of the surface with nanometer precision.[1] Z. X. Wei et al., Macromol. Rapid. Comm. 29, 290 (2008). [2] Z. X. Wei et al., Angew. Chem.Int. Ed. 44, 751-756 (2005). [3] L. M. Picco et al., Nanotechnology 18, 044030 (2007). [4] J. A.Vicary et al., Nanotechnology 20, 095302 (2009).

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16:30 Towards Ideal Morphology of Polymer Bulk Heterojunction Solar CellsAuthors : Chetan R. Singh1, Michael Sommer2,3, Marcel Himmerlich1, André Wicklein3, StefanKrischok1, Mukundan Thelakkat3 and Harald Hoppe1 1 Institute of Physics and Institute of Micro-and Nanotechnology, Ilmenau University of Technology, PF 100565, 98684 Ilmenau, Germany 2Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UnitedKingdom 3 Applied Functional Polymers, Universität Bayreuth, 95440 Bayreuth, GermanyResume : We present the thorough optimization of block copolymer (BCP) based polymer solarcells utilizing a blend of a self-assembling P3HT-b-PPerAcr BCP and a PPerAcr acceptorhomopolymer. As an effect of increasing acceptor content in the block copolymer/homopolymerblend, we observe a continuous rise in the open circuit voltage (Voc) and the short circuit current(Isc) leading to an overall improved photovoltaic performance. The improved performance withincreasing acceptor content is attributed to (a) an increase of the acceptor domain size leading toimproved charge transport and to (b) a reduced recombination of charge carriers at the cathodeinterface due to the surface segregation of the acceptor. The surface segregation of the acceptoris identified by atomic force microscopy and X-ray photoelectron spectroscopy. Furthermore weshow that by deliberately introducing an acceptor buffer layer at the cathode interface, we areable to control Voc at relatively high values (~ 640 mV), independently of the bulk heterojunctionmorphology underneath.

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16:30 Methods in determination of morphological degradation of polymer:fullerene solar cellsAuthors : Vida Turkovic, Sebastian Engmann, Gerhard Gobsch, Harald Hoppe Ilmenau TechnicalUniversity, Institute of Physics, Experimental physics 1, Weimarerstraße 32, 98693 Ilmenau,GermanyResume : The changes in the blend morphology of the thin films accelerate when thermallyannealed at increased temperatures. Tapping-mode atomic force microscopy (AFM)measurements provide deeper insight into the nano and micrometer scale of the phaseseparation observable on the surface of the film. Furthermore, to prove the coarsening of phaseseparation on various length scales, optical microscopy, UV-Vis, photoluminescence andmeasurements were conducted. Of special interest is tracking down the formation of fullereneaggregates and correlation of their growth in time. We demonstrate detecting various steps ofphase separation directly using simple optical measurements.

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16:30 Bain transformation of PCBM crystals, effects on electronic propertiesAuthors : G. Volonakis [1], L. Tsetseris [2,3] and S. Logothetidis [1] [1] Lab for Thin Films,Nanosystems and Nanometrology, Department of Physics, Aristotle University of Thessaloniki,54124 Thessaloniki, Greece [2] Department of Physics, National Technical University of Athens,Athens, Greece [3] Department of Physics and Astronomy, Vanderbilt University, Nashville, TN,USAResume : It is well established that crystals of organic semiconductors can attain differentstructures, known as polymorphs, depending on external conditions such as proximity tosubstrates, annealing, or pressure. In this work we report the results of first-principlescalculations on possible crystal structures of the organic semiconductor phenyl-C61-butyric acidmethyl ester (PCBM). In particular, we probe the so-called Bain transformation that connects in acontinuous fashion high-symmetry body-centered cubic (BCC) and face-centered cubic crystalstructures. In the PCBM case we find that Bain transformations comprise of a multitude of pathsthat are associated with different conformations of the molecules within the crystal unit cell.Because of path coexistence Bain transformations can give rise to hysteresis and may have astrong dependence on annealing conditions. The results suggest that structural characteristics ofPCBM crystals and, concomitantly, their electronic properties can be modified by controlledgrowth on suitable substrates, through of exertion of biaxial pressure, or due to intrinsic strainpresent in the case of PCBM crystallites embedded within photovoltaic systems.

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16:30 A Study of Vertical Phase Separation in P3HT:PCBM blends via Energy Dispersive X-raySpectroscopyAuthors : Sylvain Massip, Richard M. Langford and Neil C. Greenham Cavendish Laboratory,Department of Physics, University of Cambridge, J J Thomson Ave., Cambridge, CB3 0HE, UnitedKingdomResume : Although crucial for the performance of organic solar-cells, the study ofbulk-heterojunctions phase separation remains a difficult problem. In particular, the verticalphase-separation of P3HT:PCBM has recently been a much investigated but very controversialtopic (1-3). In this study, we prepare cross-sectional samples using focused ion beam (FIB)milling as reported by Loos et al. (4) and we subsequently study them by combining scanningtransmission electron microscopy (STEM) with energy dispersive X-ray spectroscopy (EDX). Thistechnique is characterised, and we find that it can reliably measure the repartition of the sulphurwithin the sample with a resolution of about 20 nm. From this data, we deduce the verticaldistribution of the P3HT and use it to describe the vertical phase separation of P3HT:PCBM blends.It is found that there is a thin P3HT-rich layer on the top of the sample (close to the aluminiumlayer). The P3HT concentration then decreases until 50-60 nm below the surface, where itreaches a minimum. Below, the P3HT concentration increases slowly until the bottom of the film

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(close to the pedot:pss). The mechanisms that lead to such phase separation and theconsequences for device physics will be discussed. (1) Y. Vaynzof et al, ACS Nano, in press (2) J.W. Kiel et al, J. Chem. Phys., 2010, 133, 074902. (3) M. Campoy-Quiles et al, Nat Mater, 2008, 7,158-164. (4) J. Loos et al, Polymer, 2002, 43, 7493-7496.

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16:30 Growth and performance of polycrystalline -Sexi-thiophene thin films deposited by SupersonicMolecular Beam DepositionAuthors : M. Tonezzer (1,2,4,5), T. Toccoli (2), S. Gottardi (2), E. Rigo (3), P. Bettotti(3), S.Iannotta (2) 1) Dipartimento di Fisica, Università di Trento, Via Sommarive 14, I-38100 PovoTrento, Italy 2) IMEM-CNR Istituto Materiali per Elettronica e Magnetismo, Parco Area delleScience 37/a, I-43100 Parma, Italy 3) Laboratorio Nanoscienze, Dipartimento di Fisica, Universitàdi Trento, Via Sommarive 14, I-38050 Povo Trento (Italy) 4) Fondazione Bruno Kessler, ViaSommarive 14, 38100 Povo (TN), Italy 5) TASC IOM-CNR National Laboratory, S.S. 14, I-34012Trieste, ItalyResume : Conjugated small molecules are very interesting both as a model to study the growthmodel of crystalline organic films and as a very good performance organic material. Vacuumdeposition is the most suitable technique to obtain high purity and order films. Nevertheless, thehigh anisotropy of organics makes easy the formation of different polymorphs or/and orientationsthat strongly limit the quality of the films. The innovative supersonic molecular beam deposition(SuMBD) technique, developed at the IFN-Lab, allows a wider control on the growth. The kineticenergy (EK) of the impinging molecules is the key factor that affects the growth modifying theassembling processes of molecules and their surface mobility. We report on the -sexithiophenesub-monolayer growth, investigating the influence of energetic state of the impinging molecules,surface energy and substrate temperature. Each growth parameter affects the morphology of themolecular film in terms of coverage and fractality of the sub-monolayer islands. Optimizing thedifferent parameters, we obtain larger and smoother islands and low density of grain-boundaries.The best conditions, including high kinetic energy of the beam, give rise to organic thin filmtransistors (OFETs) with a field effect mobility value of 1.5•10-1 V·cm-1·s-1, twice higher than thebest values in literature. This work was financially supported by Provincia Autonoma di TrentoProject Nanosmart and the Fondazione CARITRO Project ODINO.

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16:30 Impact of zinc phthalocyanine polymorphism on the interface structure of C60/ZnPcheterojunctionsAuthors : T. Djuric (a) , R. Resel (a), M. Brinkmann (b); (a) Institute of Solid State Physics, GrazUniversity of Technology, Austria (b) Institut Charles Sadron, CNRS-Université Strasbourg,Strasbourg, FranceResume : Photophysical properties and charge transport in Donor-Acceptor (D/A) systemsdepend crucially on the structure of the D/A interface and the morphology of the D and A layers.In this study, we have prepared bilayer films combining the organic p-type semiconductorzinc-phthalocyanine (ZnPc) with the electron acceptor fullerene (C60). We have focused on theimpact of the structure of the ZnPc layer on the interface formed with C60. To this aim, highlyoriented ZnPc films of the alpha and the beta forms have been grown on polycarbonate (PC)alignment layers. The detailed morphological and structural study of the bilayered films wasperformed using UV/VIS absorption spectroscopy, atomic force microscopy, transmission electronmicroscopy and x-ray diffraction. When grown at Tsub=115°C, the ZnPc films consist of uniaxiallyoriented nanocrystals of the alpha phase with a preferential (001) surface. Electron diffractionindicates that the C60 crystallites grow with a rather 'unusual' (2 1 -1) contact plane. ForTsub=200°, oriented beta ZnPc crystals are formed with a preferential (0 0 1) contact plane andthe C60 nanocrystals grow with a preferential (1 1 1) contact plane. Molecular modelling is usedto propose structural models of the D/A interfaces. In the case of alpha ZnPc films, C60 moleculesform rows that are oriented parallel to the columnar stacks of the ZnPc nanocrystals as observedexperimentally by High-Resolution Transmission Electron Microscopy.

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16:30 Substrate induced polymorphism of epitaxially oriented H2TPP thin filmsAuthors : T. Djuric (a), T. Ules (b), S. Gusenleitner (b), N. Kayunkid (c), M. Brinkmann (c), M. G.Ramsey (b), R. Resel (a); (a) Institute of Solid State Physics, Graz University of Technology,Austria (b) Institute of Physics, Karl-Franzens University Graz, Austria (c) Institut Charles Sadron,CNRS-Université de Strasbourg, Strasbourg, FranceResume : Controlling and predicting molecular packing and orientation in thin films is of crucialimportance to achieve films suitable for applications in electronic devices. We have prepared thinfilms of 5,10,15,20 tetraphenyl-porphyrin (H2TPP) by organic molecular beam deposition underultra high vacuum conditions. Two different substrates were used: KCl(100) and oxygenpassivated Cu(110) single crystals. The crystallographic structures were investigated in-situ bylow-energy electron diffraction (LEED). Ex-situ electron microscopy/diffraction (TEM/TED) andx-ray diffraction (XRD) techniques were used. The XRD specular scan reveals that the H2TPPpowder crystallizes in a tetragonal unit cell (a=b=15.125 Å, c=13.940 Å). However, whendeposited on KCl(100) the molecules adopt a different tetragonal phase (a=b=13.375 Å, c=9.735Å) with the (001) net plane parallel to the substrate. Here, the central aromatic macrocycle isparallel to KCl(100) and H2TPP grows in columnar stacks. XRD pole figure measurements of thefilm grown on Cu(110)(2x1)O, on the other hand, reveal a triclinic phase of H2TPP (a=6.44 Å,b=10.42Å, c=12.41Å, alpha=96.06°, beta=99.14°, gamma= 101.12°) with the (5 -10 3) planeparallel to the substrate surface. The macrocycle is tilted by 9° from the surface and the H2TPPmolecules align with one pair of the opposed phenyl rings along the oxygen rows. Furthermore,LEED measurements show that the formed surface unit cell is commensurable in respect to thesubstrate.

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16:30 Reflectance anisotropy spectroscopy study of copper phthalocyanine thin films grown oncrystalline and amorphous substratesAuthors : Berkovits V.L., Gordeeva A.B., Terukov E.I. A.F. Ioffe Physical-Technical Institute,194021 Saint Petersburg, RussiaResume : Thin films of organic molecular semiconductors - metallophthalocyanine are promisingmaterials to be used in electronic and optoelectronic devises. The progress in this field, however,requires systematic studies of the structural and electronic properties of the films grown oninorganic substrates of different nature [1]. Here we report reflectance anisotropy study (RAS) ofcopper phthalocyanine (CuPc) thin films grown by vacuum evaporation on GaAs(100) and glasssubstrates. Such films were found to reveal an optical anisotropy [2]. Directions of the orthogonalaxes of this anisotropy were determined from azimuth dependence of RA spectra. We found thatfor GaAs(100) substrates and film thickness <40 nm these axes almost coincide with [110] and[1-10] axes of GaAs(100) surface. This indicates that the crystalline GaAs surface strongly effectson the molecular ordering even when it is covered by a natural oxide. At the same thickness, theCuPc films grown on glass substrates reveal broader and less intensive RA spectral features thanthose observed for GaAs(100) substrates. The RA spectra of the CuPc films were calculated in aframework of the 3-layer dielectric media model. Values of structure parameters of the CuPcfilms were obtained by fitting the calculated and the measured spectra. [1] C.M. Lieder, Nature(London) 415, 617 (2202) [2] M.K. Debe, J. Vac. Sci. Technol. A10, 2816 (1992)

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16:30 GROWTH OF PARA-SEXIPHENYL ON ION BOMBARDED MICA: SHAPE INVESTIGATIONS OF 2ndLAYER ISLANDSAuthors : S. Lorbek1, Q. Shen1, D. Nabok2, T. Potocar3, A. Winkler3, P. Puschnig2, C. Ambrosch-Draxl2, C. Teichert1 1Institute of Physics, Montanuniversitaet, Franz Josef Strasse 18, A-8700Leoben, Austria 2Chair of Atomistic Modeling and Design of Materials, Montanuniversitaet, FranzJosef Strasse 18, A-8700 Leoben, Austria 3Institute of Solid State Physics, Graz University ofTechnology, Petersgasse 16, A-8010 Graz, AustriaResume : Significant progress has been made during the last decades in the application ofconjugated organic semiconductor molecules in different fields of organic electronics [1]. The goalis the production of low-cost, low-energy-consuming, flexible devices with high charge-carriermobilities. For this purpose, it is necessary to understand the initial growth stage which is crucialfor the design of growth routes resulting in defined smooth films. Here, we investigate the earlygrowth stage of para-sexiphenyl (6P) which was deposited using molecular beam epitaxy in ultrahigh vacuum on ion bombarded mica. On this amorphous surface, terraced growth moundsconsisting of almost upright standing molecules are formed [2]. Before coalescence of irregularlyshaped first layer islands, second layer islands start to grow with well defined shapes. In fact, weobserve the coexistence of two types of different elongated hexagonal islands. Transverse shearmicroscopy revealed the azimuthal molecule orientation within these islands [3]. Theexperimental observations are corroborated by molecular dynamics simulations using empiricalforce-fields leading to the crystal shapes and the orientations of islands consisting of standing 6Pmolecules. This work is funded by the Austrian Science Fund projects S9707, S9714 and P19197.[1] C.K. Chiang, et al., Phys. Rev. Lett. 39, 1098 (1977). [2] G. Hlawacek, et al., Science 321,108 (2008). [3] K. Puntambekar, et al., Adv. Funct. Mater. 16, 879 (2006).

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16:30 Tuning the use of thermal annealing to film composition in polymer:fullerene photovoltaic devicesAuthors : Andrew J. Pearson 1, Tao Wang 1, Paul E. Hopkinson 2, Athene M. Donald 2 & David G.Lidzey 1 1 Department of Physics and Astronomy, University of Sheffield, Hicks Building,Hounsfield Road, Sheffield, S3 7RH, United Kingdom 2 Department of Physics, CavendishLaboratory, University of Cambridge, JJ Thomson Avenue, Cambridge, CB3 0HE, United KingdomResume : Organic Photovoltaics (OPVs) are a candidate technology for low-cost solution-processable solar energy conversion devices. In optimised OPV architectures, these materialsmix throughout the active layer to form a nanoscale bulk heterojunction, which, upon absorptionof a photon, maximises the efficiency of free carrier generation and subsequent charge transportand extraction. While careful consideration is given to the composition of the casting solution toachieve an optimised OPV (for example, casting solvent and the blend ratio between polymer andfullerene derivative), following deposition of a blend thin-film the as-cast morphology is generallyfar from ideal for photocurrent generation. Consequently, it is therefore necessary to apply apost-deposition film treatment to maximise device power conversion efficiency (PCE). Although anumber of options are available, the use of a heat treatment, or thermal anneal, is common toalmost all polymer:fullerene blends. The focus of this work is to demonstrate how the benefits ofa heat treatment are dependent on film composition, which can be rationalised by considering thephase behaviour of the blend thin-film. We consider two polymers, poly(3-hexylthiophene)(P3HT) and poly [N-9’-heptadecanyl-2,7-carbazole-alt-5,5-(4’,7’-di-2-thienyl-2’,1’,3’-benzothiadiazole) (PCDTBT), blended with [6,6]-phenyl-C61-butyric acid methyl ester(PCBM) across the composition range [1]. Using spectroscopic ellipsometry we identify thetemperature necessary to remove residual solvent from as-cast films, and the glass transitiontemperature (Tg) of the blend. UV-Vis spectroscopy and optical microscopy techniques also showthat when heating films above Tg, a composition dependent optimum annealing temperature isfound. Annealing above this temperature can lead to excessive phase separation and a reductionin thin-film optical density. These findings are compared with the PCEs of fabricated OPVs toprovide a rational understanding of why a minimum heating temperature required for benefit andan optimum heating temperature exist. The study provides a guide to the use of post-depositionheat treatments for future high-efficiency OPVs. [1] A.J.Pearson et al. (Manuscript in Preparation)

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16:30 Influence of packing density on the dielectric and optical properties of organic crystals andmonolayersAuthors : Lorenz Romaner, Stephan Sagmeister, Peter Puschnig and Claudia Ambrosch-DraxlChair of Atomistic Modelling and Design of Materials, Montanuniversit?Leoben, Franz-Josef-Stra?18, A-8700 Leoben, AustriaResume : The response of organic crystals or organic semiconductor films to electric fields is afascinating phenomenon. It governs many properties of dielectric and optical nature, such as lightabsorption, charge injection or capacitance and is, therefore, at the heart of an understanding oforganic devices. The response is intimately linked to the structure of the organic films. Inparticular, variations in the packing density lead to a number of interesting effects such as changein band-gap, depolarization, changes in dielectric constant and corresponding shifts of excitationenergies etc. In this contribution, we employ density-functional theory (DFT) and many-bodyperturbation theory (MBPT) to model the dielectric and optical properties of 3D crystals and 2Dmonolayers of prototypical pi-conjugated organic molecules. We first study static fields where werely on conventional DFT to address depolarization and the static dielectric constant. We extendthis investigation by the use of the GW approach of MBPT which takes the influence of electronicpolarization on the bandgaps and polarizabilities of the molecules into account. In a second step,we proceed to optical phenomena by solving the Bethe-Salpeter equation. This allows addressingexcitonic properties, i.e., the influence of dimensionality and inter-molecular interaction strengthon binding energy and electron-hole delocalization. By systematically varying the packing densityof the organic molecules, we are able to quantitatively determine the relationship between thisstructural parameter and the material’s response, which aids the design and tailoring of organicfilms.

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16:30 Nanoscale in-situ characterization of thermally induced morphological changes onpolymer:fullerene thin films during annealingAuthors : A. Roigé (1), J. O. Ossó (1), M. Campoy-Quiles (2) and L. F. Vega (1) (1) MATGAS 2000AIE, Campus de la UAB, 08193 Bellaterra (Barcelona) (2) ICMAB, Campus de la UAB, 08193Bellaterra (Barcelona)Resume : Post-deposition annealing treatments have been shown to be one of the most effectivemethods to enhance performance of P3HT:PCBM based organic solar cells. One of the mostrelevant changes suffered by the material system during heating is the increased molecularmobility that leads to P3HT crystallization. This induces an enhancement in charge transport andlight absorption. Moreover, PCBM molecules diffuse through P3HT matrix forming rich-PCBMacceptor domains. In this work, we use in-situ AFM measurements during annealing ofP3HT:PCBM spin-coated thin films to detect changes in topography and surface roughness. Inaddition, to complement topographical data, in-situ Raman spectroscopy experiments areperformed in order to study the behavior between component and molecular interactions that willallow a precise identification of the thermally induced morphological transitions. Furthermore,comparison with studies of thermal transition of other materials is also presented. The closecombination of both in-situ AFM and Raman spectrosocopy measurements enables a detailednanoscale characterization of the morphological changes that P3HT:PCBM mixtures undergoduring thermal annealing which are crucial to optimize the effects of the whole annealing process.

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16:30 Room temperature detection of light at 1.55um using C60 based devicesAuthors : M.Bednorz1, T.Fromherz1, G.J.Matt1, P.Stadler2, M.Ullah1, H.Sitter1,N.S.Sariciftci2 1)Institute of Semiconductors and Solid State Physics, Johannes Kepler University,Linz, Austria 2) Linz Institute for Organic Solar Cells(LIOS), Johannes Kepler University, Linz,AustriaResume : We report on novel near to mid infra-red sensing devices utilising fullerenes asabsorbing media. Two types of devices are investigated: Si-Fulleren-Al diode structures [1] aswell as C60 organic field effect transistors. Although completely different in architecture, bothdevice types show a simlar photoresponse in the spectral range from 0.6-1.7 eV, i.e. at energiessmaller than the fundamental absorption edge of fullerens. Most important, this infra-redphotoresponse persists up to room temperature. The Si-Fulleren hetero-junction shows an almostideal diode behaviour with a current rectification of 10^6 at 300K for a bias variation from -1.5 to+1.5V and is operated in photovoltaic mode. The investigated OFET is a bottom gate geometryC60 transistor, with passivated aluminium oxide as dielectric. The drain-source current isphotosensitive, its photoresponse scales linearly with the gate voltage. For both type of devicesthe origin of the photoresponse is tentatively ascribed to the excitation of C60 anions. Thegeneration of photo-current via this common absorption process in the two different types ofdevices will be discussed in details. The scientific relevance, simple fabrication process andcompatibility with the well established silicon technology makes fullerene based infrareddetectors a promising candidates for widespread applications. [1] G. J. Matt, M. Bednorz et al.,Adv. Mat. 22 (2010), 647.

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16:30 Correlation between surface morphology and photo-electrical transport properties of bulkheterojunction solar cells based on anthracene-containing PPE-PPVAuthors : Alberto M. Ramil (a,*), Igor Beinik (b), Astrid Wachauer (b), Markus Kratzer (b), ÖzlemUsluer (a,c), Christoph Ulbricht (a), Daniel A. M. Egbe (a), Valery Bliznyuk (a,d), ChristianTeichert (b), Niyazi Serdar Sariciftci (a). (a) - Linz Institute for Organic Solar Cells (LIOS)Institute of Physical Chemistry Johannes Kepler University Altenbergerstrasse 69 Linz 4040(Austria) (b) - Institute for Physics Montanuniversitaet Leoben Franz-Josef Straße 18 8700 Leoben(Austria) (c) - Mugla University Department of Chemistry 48000 Kotekli, Mugla, Turkey (d) -College of Engineering & Applied Sciences, Western Michigan University, Kalamazoo, MI 49008,

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USA * Alberto Montaigne Ramil, Tel.: +43 732 2468 8854, FAX: +43 732 2468 8770, Email:[email protected] : This work presents results on the charge carrier transport properties of a systemcomposed of a side chain statistical anthracene-containing copolymer, AnE-PVstat,[1] and a1-(3-methoxycarbonyl)propyl-1-phenyl-(6,6)-C61 (PCBM) as an electron acceptor. AnE-PVstat–PCBM blends of different ratios were prepared in a common solvent and spin-coated onglass/ITO/PEDOT substrates. Traditional contact and non-contact mode Atomic Force Microscopy(AFM), and photoconductive AFM (PC-AFM) techniques were applied for characterization of thefilms morphology and their nanoscale photoconductivity properties. Blended polymer filmsshowed characteristic micro-domain structures with the average size of domains dependable onthe ratio of the co-polymer components. The charge carrier transport properties of the bulkheterojunction solar cells based on AnE-PVstat – PCBM system were also addressed with current-voltage measurements and charge carrier extraction by linearly increasing voltage (photo-CELIV)technique. For this aluminum electrodes were thermally evaporated on the films as a top contact.We report on the correlation between the samples’ morphology and their photoelectrical andcharge mobility properties at micro and nano scale. references: [1] Egbe, D. A. M.; Adam, G.;Pivrikas, A.; Ramil, A. M.; Birckner, E.; Cimrova, V.; Hoppe, H.; Sariciftci, N. S. J. Mater. Chem.2010, 20, 9726-9734.

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16:30 Color appearance modification as an analytical tool to monitor surface interactions of organicnanocrystalsAuthors : K. Nauka, Hou T. Ng Hewlett-Packard Laboratories, 1501 Page Mill Road, Palo Alto, CA94304, USAResume : Organic nanocrystals facilitating operation of organic electronic devices and employedas colorants in display and printing applications frequently undergo surface reactions with vicinalorganic species that can either advantageously or deleteriously modify their properties. Ourprevious work showed that the surface modifications can be detected with the help of surfacesensitive IR reflectance measurement of the selected nanocrystal's vibrational modes (K.Naukaet al., Fall 2010 E-MRS Meet.). Present work demonstrates that even simpler analytical techniquerelying on monitoring visible color changes of the selected organic nanocrystals can provideinformation about their surface interactions. These color changes can be measured with astandard color analyzer used in printing applications or, in some applications, even with a nakedeye. The observed color changes expressed in terms of the CIE (Commission Internationaled'Eclairage) L*a*b* color coordinates have been associated with specific modifications of thenanocrystals' surface simultaneously characterized with the help of FTIR, XPS, and surfacesensitive XRD. Specific examples of the nanocrystals' surface modifications and the associatedcolor changes will be discussed using the example of Cu-phthalocyanine and several othernanocrystalline organic electronic materials.

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16:30 Functionalized graphene/(poly 3-hexyltiophene) based nanocomposites filmsAuthors : Alexandru C. Obreja, Dana Cristea, Raluca Gavrila National Institute for Research andDevelopment in Microtechnologies (IMT-Bucharest), Bucharest, RomaniaResume : Thin-film nanocomposites were obtained by depositing the mixture solutions fromfunctionalized graphene and rr-P3HT on transparent substrates. Solubility of functionalizedgraphene in common organic solvents-P3HT polymer mixtures showed a good stability andfacilitated the spin-coating and drop-casting processes. The nanosize particles in deposited filmswere characterized by Fourier transform infrared spectroscopy, atomic force microscopy, X-raydiffraction, Scanning electron microscopy and Raman spectroscopy. An enhanced cristallinity andstable mobility due to the existing of a strong electronic pi-pi interaction between functionalizedgraphene and rr-P3HT was observed. The I-V characteristics recorded of micropatterned films atambient temperature shown that the degree of functionalization on graphene have a majorimportance on the charge carrier mobilities. These findings indicate that the addition offunctionalized graphene enhance the performance of thin film polytiophene materials.

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16:30 Nanomechanical Properties of PEDOT:PSS thin filmsAuthors : S. Kassavetis, P. Karagiannidis, C. Koidis, and S. Logothetidis Laboratory for Thin Films– Nanosystems and Nanometrology (LTFN), Physics Department, Aristotle University ofThessaloniki, GR-54124 Thessaloniki, GreeceResume : Nowadays intensive research activities are observed in the field of optoelectronicsdevices based on organic materials (OEDs) and mainly for the fabrication of such devices onflexible polymer substrates. Such devises are subjected to bending that causes mechanicalstresses to the devise functional layers and as a consequence the device service life is affected.In this study depth sensing dynamic and quasistatic nanoindentation was used to measure themechanical properties of PEDOT:PSS thin films. PEDOT:PSS, a key conductive material for OEDs,was grown using different deposition techniques, such as spin coating and roll-to-roll gravureprinting. A Berkovich diamond indenter was used to indent the PEDOT:PSS films and thenanoindentation load-displacement curves were analyzed to estimate the elastic modulus (E).The E values (≈3 GPa) of the different thin films were very close and in accordance with thosemeasured using other mechanical characterization techniques. Differences were found on thetime-depended deformation (creep) of the PEDOT:PSS thin films. The remained waterpercentage, measured by spectroscopic ellipsometry, in the case of the printed films and thepresence of additives in the case of spin-coated ones, were found to affect the deformation of thePEDOT:PSS due to creep. The results were compared with the grain size measured by AtomicForce Microscopy.

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16:30 OPTICAL AND ELECTRICAL PROPERTIES OF ARYLENEVINYLENE COMPOUNDS THIN FILMSPREPARED BY VACUUM EVAPORATIONAuthors : O. Rasoga1, L. Vacareanu2, M. Grigoras2, M. Enculescu1, M. Socol1, F. Stanculescu3, I.Ionita3, A. Stanculescu1 1 National Institute for Laser, Plasma and Radiation Physics, Str.Atomistilor, Nr. 409, PO Box MG-36, Magurele, Bucharest, 077125, Romania 2 P. Poni” Institute ofMacromolecular Chemistry, 41 A Gr. Ghica Voda Alley, 700487-Iasi, Romania 3Faculty of Physics,University of Bucharest, Str. Atomistilor nr.405, P.O.Box MG-11, Bucharest-Magurele, 077125RomaniaResume : The aromatic amines like triphenylamines and carbazoles could be used as buildingblocks for the preparation of conjugated oligomers and polymers, potential candidates foroptoelectronic applications. Two arylenevinylene oligomers, 1,4-bis[4-(N,N’-diphenylamino)phenylvinyl] benzene and 3, 3’-bis (N-hexylcarbazole)vinylbenzene havebeen used to prepare, by vacuum evaporation, thin films on different substrate [n, p type (111)single crystal silicon, ITO, glass). The particularities of the molecular structures associated withthe donating groups situated at the ends linked by conjugated bridges can determine largetwo-photons absorption cross-section, high transmission in visible range and reduced steric effectthat improves the conduction. The thin film morphology was investigated by SEM and AFM, thestructure by XRD and the optical properties by UV-VIS, FTIR and Luminescence Spectroscopy.Spectro-ellipsometry has been used to evaluate the thickness and optical constants. Opticalnonlinear phenomena, such as the fluorescence emission associated with the two photonsabsorption has been evidenced in the thin films of these compounds. We have also investigatedthe electrical properties of different types of SIS (Si/oligomer/Si; Si/oligomer/ITO) and MIS(Au/oligomer/Si; Au/oligomer/ITO) heterostructure emphasising the effect of the illumination onthe electrical conduction in correlation with the morphological and structural properties.

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16:30 Kelvin Probe Force Microscopy Study of aromatic type SAM Modified ITO SurfaceAuthors : S. Okur1*, Hasan Aydin1, Nesli Yagmurcukkardes1, Mavise Seker1, Ali Kemal Havare2,Serafettin Demic2, Mustafa Can2 1Izmir Institute of Technology, Department of PhysicsUrla/Izmir/TURKEY 2 Energy Department, Institute of Solar Energy, Ege University,Bornova/Izmir, TurkeyResume : One of the most important issues in OLED devices is to be able to controlelectrode/organic interface reducing the difference between the work function of anode (ITO) andHOMO level of the organic semiconducting hole transport layer (HTL) material. This differencecan cause high turn on voltage, low efficiency and restricts hole-injection [1-2]. The work functionof a metal electrode by SAM formation is one of the key issues necessary to improve the carrierinjection in organic electronic devices. [2] In this work, small molecules with aromatic structureswith single and double carboxylic acid functional groups have been used as self-assemblymonolayer (SAM) to modify ITO surface. SAM molecules with 1mM were prepared at roomtemperature in ethanol solution. ITO substrates were kept in ethanol-SAM solution for 48 hours tobe covered with SAM monolayer. QCM technique was used to monitor the SAM formation process.Our Kelvin Probe Force Microscopy (KPFM) measurements showed that the surface potentialsincreased more than 100 mV with reference to bare indium tin-oxide. The Schottky barrierparameters have been obtained from I-V measurements. The results show that the thresholdvoltage on OLEDs with modified ITO is lowered to one quarter compare to OLEDs with unmodifiedITO. [1] C.N. Li, C.Y. Kwong,A.B. Djurisic,P.T., Thin Solid Films 2005, 477,57-62 [2] Y.Rosenwaks, R. Shikler, Th. Glatzel, S. Sadewasser, Phys. Rev. B.,2004, 70,08532

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16:30 DEPOSITION AND ANALYSIS OF NANO-SIZED THIN FILMS OF LANTHANIDE AROMATICCARBOXYLATESAuthors : V. Utochnikova*, A. Kalyakina, O. Kotova, N. Kuzmina Department of Material Sciences,Lomonosov Moscow State University, Leninskie Gory 1/3, 119991 Moscow, Russia e-mail:[email protected] : Metal-organic coordination compounds have already shown themselves as prospectiveemitting materials in organic light-emitting diodes, but some of them have demonstrated verybad film-forming properties. So lanthanide aromatic carboxylates, Ln(Carb)3, possess goodluminescent properties and ultraviolet durability, but their polymeric structure prevent thin filmsdeposition by convenient vacuum- and solution-processable methods. By the example of terbiumo-substituted benzoates we present here two new chemical approaches to thin film deposition ofpractically nonvolatile and insoluble coordination compounds. The first one is based on exchangereaction between volatile precursors in the gas phase (Hdpm – dipivaloylmethane): Tb(dpm)3↑ +3HCarb↑ → Tb(Carb)3↓ + 3Hdpm↑ While the second one deals with deposition of thin films ofsoluble ternary complexes Tb(Carb)3(Q)n (Q – neutral donor ligand) via spin-coating with theirfollowing thermal decomposition in films: Tb(Carb)3(Q)n → Tb(Carb)3 + nQ↑ As these techniquesinclude chemical reaction in the thin films, film analysis was to be focused on both themorphology and the film composition to prove that no by-product impurities are present. Thecombination of spectroscopic methods: 1) IR and Raman spectra, 2) steady-statephotoluminescence spectra, 3) excited state lifetime (Tb(III); 5D4); 4) excitation spectra – wassuccessfully used for analysis of film composition. Nano-sized thin films of pure Tb(Carb)3 withaverage roughness of ~4 nm were deposited by new techniques. The correlations betweendeposition conditions and film composition and morphology as well as the prospects of newapproaches suggested are discussed. This work is supported by RFBR (grant № 09-03-00850-a).

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16:30 Exciton vs. Excimer Coupling in Molecular SheetsAuthors : Johannes Gierschner (1), Seong-Jun Yoon (2), Soo Young Park (2) (1) Madrid Instituteof Advanced Studies, IMDEA Nanoscience, Madrid, Spain (2) Center for Supramolecular

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Optoelectronic Materials and WCU Hybrid Materials Program, Department of Materials Scienceand Engineering, Seoul National University, Seoul, KoreaResume : The rational design of conjugated organic materials with defined electronic, optical andphotophysical properties in the solid state suffers from the complex interplay of intra- andintermolecular contributions. Within the last years we have thus explored a number ofstructurally and electronically well-defined oligomeric materials which form single-crystalline solidstate phases.[1,2] By doing so, the intramolecular structural motifs can be detected, which giverise to a specific intermolecular arrangement to generate a desired optical and/or photophysicalfunctionality. Like this different intermolecular coupling situations can be approached, e.g.herringbone vs. -stacks, H-type vs. J-type aggregation and excitons vs. excimers. The latterdichotomy is of peculiar importance, since it not only strongly alters the optical bandshapes, butalso impacts exciton and charge transport in molecular crystals. We have recently explored anovel p-distyrylbenzene-based compound, which forms molecular sheets due to the specificinteractions of the included cyano-functionality. The easy sliding along the sheets allows for afacile manipulation of the intermolecular arrangement by external stimuli in two distinctivepolymorphs. Strong H-aggregation is observed in one polymorph, together with excitonicfeatures of photoluminescence (PL). The second polymorph shows weaker H-aggregation, butexcimeric PL feature. All observations can be rationalized in a simple quantum-chemical scheme.Interestingly, despite H-aggregation, PL quantum yields are unusually high, suggesting low trapconcentrations ascribed to the simple uni-dimensionality of the crystal. [1] J. Gierschner, M. Ehni,H.-J. Egelhaaf, B. Milián Medina, D. Beljonne, H. Benmansour, G. C. Bazan, J. Chem. Phys. 123(2005) 144914. [2] S.-J. Yoon, J. W. Chung, J. Gierschner, K. S. Kim, M.-G. Choi, D. Kim, S. Y.Park, J. Am. Chem. Soc. 132 (2010) 13675–13683.

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16:30 Fabrication and characterization of fiber-like nanostructured polymer films for organicphotovoltaic applicationsAuthors : David Moerman, Olivier Douhéret and Roberto Lazzaroni Laboratory of Chemistry forNovel Materials, University of Mons / Materia-Nova, B-7000 Mons, BelgiumResume : The active layer of organic based solar cells usually consists of a bulk heterojunction(BH) blend from a polymer and a fullerene derivative as electron donor and acceptor materials,respectively. The molecular order in the BH blend is shown to play a key role in the transport ofthe electronic excitations towards the donor/acceptor interfaces where dissociation into freecharges takes place. It also ensures the charge transport towards the electrodes via appropriatepercolation paths. Further, control of the polymer material ordering at the nanoscale will affectthe transport and further contribute to ultimately adjust the blend morphology, hence yeildingimprovement of the device efficiency. In this poster we present how to control the fabrication, insolution, of nanostructured poly(3-hexylthiophene) (P3HT), an electron donor polymer, togenerate fully nano-fibrillar spin-coated thick films. The fibrillar organization of P3HT in solution isshown to be kept once mixed with the acceptor material ([6,6]-phenyl-C61-butyric acid methylester or PCBM). This allows deposition of OPV blends with controlled morphology. Thecontribution of these nanostructures to the improvement of the photovoltaic performances of thecorresponding device is finally evidenced.

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16:30 Morphological characterization of Anthradithiophene deposition by Atomic Force MicroscopyAuthors : Noham Sebaïhi,1 Olivier Douhéret2, Pascal Viville2 and Roberto Lazzaroni1 Laboratoryfor Chemistry of Novel Materials, 1 University of Mons-UMONS, 2 Materia-Nova, Mons, BelgiumJean-Yves Balandier and Yves Geerts Laboratory of Polymer Chemistry, Free University ofBrussels-ULB, Brussels, BelgiumResume : Π-conjugated materials are being increasingly used as active semiconducting elementsin organic optoelectronic devices such as field-effect transistors (FET), light-emitting diodes orphotovoltaic cells. A number of these have now demonstrated useful FET performances likepentacene reaching high values of carrier motilities that exceed that in amorphous silicon FET’s.However, this very compound suffers from oxidative instability and low solubility in commonsolvents, which makes it incompatible with low-cost solution deposition methods. Many attemptshave been made to overcome these problems and one of them consists in synthesizinganthradithiophene (ADT) which molecular structures and morphological and electrical propertiesare expected to be rather similar. This molecule is, besides, more oxidative stable and can beeasily substituted by chemical groups to enhance morphological arrangement in films andsolubility for processing. Furthermore, it has been previously showed that anthradithiopheneexhibit hole motilities (0.06-0.15 cm2/V.s) approaching that of pentacene. The charge transportmechanism in all these molecular structures is ruled by the interplay between electronicstructures within the molecular assembly. It is, therefore, of primary importance to understandthe mechanism ruling the molecular arrangement upon deposition processes especially at theirearly growth stages. In this work, morphology of pristine ADT deposited by evaporation uponhigh vacuum has been investigated by means of atomic force microscopy (AFM). Self-assemblednanostructures are evidenced. Terrace like topography is observed and attributed to verticalalignment of the molecule in good consistency with what previously reported. The influence of thegrowth rate and substrate temperature upon growth have been analyzed to define processingparameters likely to yield maximum nucleation for complete self-assembled morphology.

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Morphology and OPV Devices III (Joint with Symposium S) : Dana Olson

08:30 High-efficiency polymer-based single-layer solar cells based on molecular infiltration of theacceptorAuthors : B. Liu*,(a) R.Q. Png,(a) L.H. Zhao,(b) Richard Friend,(a,c) L.L. Chua,(b,a) P.K.H. Ho(a) Affiliations: (a) Dept of Physics, (b) Dept of Chemistry, National University of Singapore, (c)Cavendish Laboratory, University of CambridgeResume : We describe a novel molecular infiltration method to fabricate polymer-based solarcells. The donor polymer film is first deposited and photocrosslinked using a versatilehigh-efficiency nitrene chemistry, and the molecular acceptor is then “doped” into this film bycontact with its solution. The amount of molecular acceptor can then be precisely metered intothe donor film with good control over the donor-acceptor phase morphology. We have thussystematically optimised the power conversion efficiency (PCE) of regioregular poly(3-hexylthiophene) (rrP3HT):phenyl-C61-butyrate methyl ester (PCBM) solar cells using theseback-infiltrated heterostructures (BIH) by mapping their PCE as a function of the effective amountof rrP3HT and PCBM in the film. The results reveal for the first time a “ridge of efficiency” thatcoincides with the 1:1 P3HT:PCBM weight ratio line comprising islands of particularly highefficiencies at both low and high film thicknesses (maximum PCE, 5.2%). The PCE are generally20-30% higher than blend films of the same composition made by conventional spin-casting. Wewill discuss new insights into a new parameter previously neglected that controls the PCE oforganic solar cells. Together with separate control over both the donor and acceptor phases thatis now possible and compatible with roll-to-roll processing, the high performance obtainedsuggests that BIH solar cells are very interesting both for fundamental studies and commercialapplications.

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08:45 3D nanoscale ordered architectures in thin films for organic electronicsAuthors : S. Cataldo*, C. Sartorio, S. Fabiano, B. Pignataro Dipartimento di Chimica “S.Cannizzaro”, Università degli Studi di Palermo V.le delle Scienze, Ed.17 – 90100 Palermo (Italy) F.Giannazzo CNR-IMM, Strada VIII, 5 - 95121 Catania (Italy)Resume : Order in molecular thin films is of fundamental importance to gain and exploit a seriesof properties in nanotechnology. In this contest, engineering 2D supramolecular and molecularsuperstructures is of particular interest. They offer great possibilities for several applicationswhose achievement also allows for new theoretical approaches and nanoscale laws [1]. A naturalextension of 2D nanopatterning concerns the attainment of a 3D nanoscale control in molecularfilms [2]. This question is complex to challenge and it is of ultimate importance in emerging fieldslike organic and hybrid photovoltaics, organic thin film transistors and sensors as well as plasticelectronics. For example, the development of nanostructured bi-continuous bulk heterojunctions(BHJs) is an important advancement leading to improved photovoltaic power conversionefficiency (PCE) with respect to planar heterojunctions. In a previous work we obtained PCE ofabout 3 % employing the BHJ concept for all-polymer solar cells [3,4]. In this study, we show aninnovative approach for the construction of 3D ordered and modulable BHJs architectures of twodifferent polymer blends: Poly(3-hexylthiophene-2,5-diyl):Phenyl-C61-butyric acid methyl ester(P3HT:PCBM) and Poly(3-hexylthiophene-2,5-diyl):Poly(9,9-dioctylfluorene-alt-benzothiadiazole)(P3HT:F8BT). When exposed to light irradiation, these blends give rise to two differentmechanism of electro-optical interaction: Charge Transfer (CT) and the Forster Resonance EnergyTransfer (FRET), respectively. The Multilayer planar Heterojunctions (MHJs) prepared by a LSlayer-by-layer deposition, were thermally annealed. In this way, the layers within the filmundergo thermal mixing, turning pristine MHJs into a BHJs in a controlled way. Resulting BHJs arecharacterized by a polymer domain size of the order of the exciton diffusion length. AFM andESCA analyses clearly show the possibility to modulate the 3D film architecture by thermalannealing treatment. UV-VIS and Photoluminescence spectroscopy investigations also revealdrastic changes in the optical properties of the BHJ films that confirm the changes of their 3Darrangement. Moreover, Tunnelling-AFM (TUNA) studies on the films show the formation ofbi-continuous conductive vertical pathways within the BHJ that could ideally join the electrodes ofan electronic device, ensuring charge extraction. Here we show a low-cost solution processingmethod to easy control the 3D order of BHJ thin films. Tuning the structure on the scale of theexcitonic diffusion length is essential to optimize the efficiency of both CT and FRET mechanism,that are central for high performance organic electronic devices. 1. B. Pignataro J. Mater. Chem.19 (2009) 3338-3350. 2. S. Fabiano, B. Pignataro, Phys. Chem. Chem. Phys.DOI:10.1039/C0CP01012J. 3. S. Cataldo, S. Fabiano, F. Ferrante, F. Previti, S. Patanè, B.Pignataro Macrom. Rapid Commun., 31 (2010) 1281-1286. 4. See also Noteworthy Chemistry (30

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August 2010), a news weekly published by ACS.add to my program

09:00 Composite of Block copolymer with fullerene towards thermodynamically stable nano-structureactive layers for efficient organic solar cellsAuthors : Véronique Gernigon*1, Fanny Richard1, Nicolas Leclerc2, Patrick Lévêque1, CyrilBrochon3, Georges Hadziioannou3 and Thomas Heiser1 1 Institut d’Electronique du Solide et desSystèmes, UdS-CNRS, Strasbourg, FRANCE. 2 Laboratoire d’Ingénierie des Polymères pour lesHautes Technologies, UdS-CNRS, Strasbourg, France 3 Laboratoire de Chimie des PolymèresOrganiques, UB1-CNRS, Bordeaux, France * [email protected] : Polymer/fullerene bulk heterojunction solar cells use an interpenetrating network ofπ-conjugated electron-donor (D) polymers and electron-acceptor (A) C60 as active layer. Thecurrently most investigated blends consisting of regioregular poly(3-hexylthiophene) (rr-P3HT)and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) lead to energy conversion efficiencies(PCE) up to 5%. The active layer nanostructure determines to a great extend the overall deviceperformances. One possible route to a stable D/A nanostructure consists in using semiconductorblock copolymers which self-assemble into D/A heterojunctions by microphase separation. In thiswork, we explore rod-coil block copolymers blended with PCBM in view of their utilization inphotovoltaic (PV) devices. The copolymers are based on a P3HT rod block and poly(4-vinylpyridine) (P4VP) coil block. The copolymer self-assemble into nano-domains rich in eitherP3HT or P4VP, while the strong chemical affinity of P4VP with PCBM leads to accumulation of thelatter in the P4VP domains, providing them a D character. This strategy has allowed us recentlyto achieve PV devices with a 1.2% PCE and a thermally stable nano-morphology. Here weinvestigate the thin film morphology of P3HT-P4VP/PCBM blends and the related charge transportproperties for various PCBM contents and different rod-coil ratios. The film morphology has beenanalyzed by AFM while charge transport was analyzed using field-effect transistors. It is foundthat a well-ordered, thermally stable, lamellar structure, field effect mobilities can be achieved,depending on the rod/coil ratio, on the C60 loading and thermal annealing. The results arerationalized in terms of copolymer microphase separation in the presence of PCBM molecules.

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09:15 Altering the Degree of Solvent-Induced Phase Separation in P3HT:PCBM Based BulkHeterojunctionsAuthors : Teddy Salim*1, Lydia Helena Wong1, Shuangyong Sun1, Björn Bräuer2, Zhenan Bao3,Yeng Ming Lam1 1 School of Materials Science and Engineering, Nanyang Technological University,Blk N4.1, Nanyang Avenue, Singapore 639798. 2 Stanford Institute for Materials and EnergyScience, Stanford University, CA 94025, USA 3 Department of Chemical Engineering, StanfordUniversity, Stanford, CA 94305, USAResume : One of the important criteria to achieve high efficiency organic bulk heterojunction(BHJ) photovoltaics (OPV) is the control of the blend morphologies. Solvent additive method,which employs the addition of small amount of high boiling point solvent into the blend of donor(D) and acceptor (A) materials, has recently gained attention as one simple yet effective methodto induce the D-A phase separation in the blend, thereby optimizing its morphology for excitondissociation and charge transport. Despite numerous evidence of successful application of suchconcept for BHJ OPVs, the selection rule of appropriate solvent has yet to be fully established. Inthis work, we conducted a systematic study of the effect of the length of alkyl groups ofalkanedithiol-based additives on the phase separation behavior of poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric methyl ester (P3HT:PCBM) blends, and hence the OPV devicecharacteristics. The phase separation phenomenon can be correlated with both the boiling pointof the solvent additive and degree of interaction of the additive with PCBM, which is furthersupported by characterization techniques using grazing incidence X-ray diffraction (GIXRD) andscanning transmission X-ray microscopy (STXM). We discovered that optimized phase separationcan only be achieved with a proper consideration of both the boiling point and the degree ofintermolecular interaction. Power conversion efficiency (PCE) as high as 3.1% can be achieved inthe optimally phase-separated blend due to the improved exciton dissociation and reducedcharge recombination. Extension of the concept with other dihaloalkane additives also results indevices with PCE exceeding 3%, even in the absence of thermal annealing. Furthermore, we willalso demonstrate that the same concept can also be applied for P3HT nanofiber:PCBM system,suspended in non-halogenic solvent, which results in device PCE around 3%. The versatiletechnique opens up the possibility of fabricating device without any additional heat treatment andeliminating the need to use the halogen-based environmentally unfriendly solvents.

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09:30 Structural evolution of non-planar phthalocyanine thin films for near-infrared sensitive solar cells.Authors : Karolien Vasseur* 1,2; David Cheyns 1; Barry Rand 1; Ludo Froyen 2; and PaulHeremans 1,3 1 imec, Kapeldreef 75, B-3001 Leuven, Belgium 2 Katholieke Universiteit Leuven,Department of Metallurgy and Materials Engineering, Kasteelpark Arenberg 44, B-3001 Leuven,Belgium 3 Katholieke Universiteit Leuven, Department of Electrical Engineering, KasteelparkArenberg 10, B-3001 Leuven, BelgiumResume : Extending the photosensitivity of organic active layers to the near-infrared (NIR)region is one of the key factors to increase (tandem) solar cell performance by broadening thespectral overlap. Among small-weight semiconductors, non-planar phthalocyanines (Pc) such asPbPc and TiOPc are promising donor materials because of their high absorption coefficients andchanging optoelectronic characteristics upon phase transition. If this transition includes a changein crystal structure from monoclinic (M) to triclinic (T), a broadening and red-shift of theabsorption spectrum arises from the increased intermolecular interaction in this packingarrangement. Here, we aim to gain insight in the structural evolution of non-planar Pc donorlayers as a function of deposition conditions to achieve NIR-sensitive solar cells. In the case of

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PbPc, through comparison of absorption and external quantum efficiency (EQE) spectra with X-raydiffraction measurements on 10 to 60 nm-thick films, we show that the layer structure isasymmetric with a poorly crystalline monoclinic film close to the substrate, evolving to a mainlytriclinic structure in the upper part of the film. The PbPc layers with a higher T/M ratio result in asubstantial increase in short circuit current density, due to the change in absorption combinedwith the estimated twofold increase of exciton diffusion length. An optimized solar cell yields apower conversion efficiency of 3.2% with an EQE of 39% at λ = 910 nm.

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09:45 Modifying the Active Layer Morphology as a Route to High Efficiency Small Molecular TandemOrganic PhotovoltaicsAuthors : Edward New*, Thomas Howells, Paul Sullivan, Tim Jones, Department of Chemistry,University of Warwick, Coventry, CV4 7AL, U.K.Resume : Tandem organic photovoltaics (OPV) have been shown as effective methods forincreased photon harvesting compared to conventional single cell structures with efficienciesapproaching 8%. In this work we focus on modifying the active layer morphology to increaseexciton dissociation and charge transport within small molecular OPVs to obtain an improvedphotocurrent and higher overall efficiency and implement these within a tandem structure. Bothcodeposition of active layers, for increased exciton dissociation, and employing a structuraltemplating layer of 3,4,9,10-perylene tetracarboxylic acid PTCDA to alter the alignment ofsubsequent layers and improve the charge transport within the active layers have beeninvestigated. A systematic study of aluminium phthalocyanine chloride ClAlPc:C60 bulkheterojuntion (BHJ) single cells of varied donor:acceptor (D:A) ratios has shown a dependence onshort circuit current density (Jsc) with acceptor ratio in the blend. An increase of 60% in Jsc wasfound with a 1:3 D:A ratio. In the tandem OPV, the lowest performing 3:1 BHJ allowed for bestcurrent matching of subcells and gave a 10% improvement over planar cell. Further increase inperformance was found when employing the structural templating layer. A high voltage of 1.89Vand an increase in Jsc and fill factor of 4.76 mAcm-2 and 0.57, from an improved currentmatching between subcells, was obtained and produced a high efficiency device of 5.13%.

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10:00 Coffee Break

Morphology and OPV Devices IV (Joint with Symposium S) : Chris McNeill

10:30 INVITED: The Influence of Thermal and Solvent Annealing on the Morphology of Polymer–Fullerene BlendsAuthors : Michael F. Toney*, Eric Verploegen, (Stanford Synchrotron Radiation Lightsource, SLACNational Accelerator Laboratory) Rajib Mondal, Christopher J. Bettinger, Seihout Sok, Zhenan Bao(Department of Chemical Engineering, Stanford University)Resume : Bulk heterojunction (BHJ) solar cells consist of an interpenetrating blend of asemiconducting polymer and a fullerene. Both the nanoscale morphology of the two-phase filmand the molecular packing within the polymer and fullerene are tremendously important todevice performance. We have used grazing incidence X-ray scattering (GIXS) to investigate themorphology of poly(3-hexylthiophene) (P3HT)–phenyl-C61-butyric acid methyl ester (PCBM) thinfilm BHJs as a function of thermal and solvent annealing temperature (up to 220 °C). We usedboth in situ GIXS during annealing and corroborating measurements on films annealed with athermal gradient. With these techniques, we observe the following: the melting points of eachcomponent, an increase in the P3HT coherence length with annealing below the P3HT meltingtemperature, the formation of well-oriented P3HT crystallites with the (100) plane parallel to thesubstrate, when cooled from the melt, and the cold crystallization of PCBM associated with thePCBM glass transition temperature. The incorporation of these materials into BHJ blends affectsthe nature of these transitions as a function of blend ratio. These results provide a deeperunderstanding of the physics of how thermal annealing affects the morphology of polymer–fullerene BHJ blends and provides tools to manipulate the blend morphology to develophigh-performance organic solar cell devices.

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11:00 Characterisation of vertical phase separation in polymer:fullerene blend films for photovoltaics bydSIMS and NEXAFSAuthors : Ana Sofia Anselmo*, Department of Physics and Electrical Engineering, KarlstadUniversity, Sweden Andrzej Dzwilewski, Department of Physics and Electrical Engineering,Karlstad University, Sweden Jakub Rysz, Institute of Physics, Jagiellonian University, Kraków,Poland Andrzej Bernasik, Faculty of Physics and Applied Computer Science, AGH University ofScience and Technology, Kraków, Poland Andrzej Budkowski, Institute of Physics, JagiellonianUniversity, Kraków, Poland Mats Andersson, Department of Chemical and Biological Engineering,Chalmers University, Gothenburg, Sweden Jan van Stam, Department of Chemistry andBiomedical Sciences, Karlstad University, Sweden Krister Svensson, Department of Physics andElectrical Engineering, Karlstad University, Sweden Ellen Moons, Department of Physics andElectrical Engineering, Karlstad University, SwedenResume : Morphological control and characterization of blend films is key in the development ofviable polymer solar cells. Spontaneous formation of vertical compositional gradients duringsolution processing has been shown for polyfluorene:PCBM blends and rationalized withthermodynamic and kinetic models of nucleation and spinodal decomposition.[1, 2] The extent ofvertical stratification is affected by polymer side-chain modification aimed at controllingpolymer:fullerene miscibility.[3] Here we present high-resolution film morphology results forseveral polymer:fullerene systems as obtained from near-edge X-ray fine structure spectroscopy(NEXAFS) in partial and in total electron yield modes. Blend films were found to be polymer-enriched at the surface. Dynamic secondary ion mass spectrometry (dSIMS) and NEXAFS givecompositional information at different depths, resulting in a more complete picture of the film

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morphology. 1. Björström, C.M. et al, Multilayer formation in spin-coated thin films oflow-bandgap polyfluorene:PCBM blends, J. Phys.:Condens. Matter. 2005 17 L529; 2. Nilsson, S.et al, Morphology and Phase Segregation of Spin-Casted Films of Polyfluorene/PCBM Blends,Macromol. 2007 40 8291; 3. Anselmo, A.S. et al, Tuning the vertical phase separation inpolyfluorene:fullerene blend films by polymer functionalisation (submitted to Chem. Mater.).

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11:15 Surface-Directed Spinodal Decomposition in Poly[3-hexylthiophene] and C61-Butyric Acid MethylEster BlendsAuthors : Yana Vaynzof*1, Dinesh Kabra1, Lihong Zhao2, Lay Lay Chua2, Ullrich Steiner1, andRichard H. Friend1,2 1 Cavendish Laboratory, JJ Thomson Avenue, Cambridge-CB3 0HE, U.K. 2Department of Physics, National University of Singapore, 117542 SingaporeResume : Demixed blends of poly[3-hexylthiophene] (P3HT) and C61-butyric acid methyl ester(PCBM) are widely used in photovoltaic diodes (PV) and show excellent quantum efficiency andcharge collection properties. As we recently reported in [1] we find the empirically optimizedliterature process conditions give rise to demixing during solvent (chlorobenzene) evaporation byspinodal decomposition. Ultraviolet photoemission spectroscopy (UPS) and X-ray photoemissionspectroscopy (XPS) results are consistent with the formation of 1 - 2 nm thick surface layers onboth interfaces, which trigger the formation of surface-directed waves emanating from both filmsurfaces. These composition waves are confirmed using an XPS depth profiling technique, whichprobes chemical surface composition with XPS and uses ion gun sputtering of the film to achievedepth resolution. This observation is evidence that spinodal demixing (leading to a bicontinuousphase morphology) precedes the crystallization of the two components. We propose a model forthe interplay of demixing and crystallization which explains the broadly similar PV performancefor devices made with the bottom electrodes either as hole or electron collector. The processregime of temporal separation of demixing and crystallization is attractive because it provides away to control the morphology and thereby the efficiency of PV devices. [1] Y. Vaynzof et al, ACSNano, in press (DOI: 10.1021/nn102899g)

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11:30 Studying the vertical diffusion of PCBM in P3HT using Organic Field-Effect TransistorsAuthors : John G. Labram*, Donal D.C. Bradley, Thomas D. Anthopoulos Department of Physics,Imperial College LondonResume : Recent progress in the field of organic field-effect transistors (OFETs) has beenimpressive, and OFETs are now beginning to surpass amorphous silicon-TFTs in terms ofperformance and cost.1 In addition to their technological applications, OFETs are also consideredexcellent test-beds for studying the characteristics of semiconducting material systems. It hasrecently been shown2 that the clustering of fullerenes in polymers can be probed in-situ usingOFET mobility measurements. Here we extend this study to probe the vertical diffusion offullerenes in polymers. By employing a P3HT:PCBM bilayer structure, the channel of abottom-gate OFET device can be made initially p-type only. By annealing the device andmonitoring the appearance and evolution of electron current, and hence electron mobility, thediffusion of PCBM in P3HT can be studied. More specifically, by measuring the time-dependence ofelectron mobility evolution, and modelling the diffusion using Fick’s second law, an approximationof the diffusion coefficient can be made. Detailed understanding of this process is critical for thestudy and further improvement of bulk-heterojunction organic solar cells. 1. R. Hamilton, J.Smith, S. Ogier, M. Heeney, J. E. Anthony, I. McCulloch, J. Veres, D. D. C. Bradley and T. D.Anthopoulos, Adv Mater 21 (10-11), 1166-1171 (2009). 2. J. G. Labram, E. Buchaca Domingo, N.Stingelin, D. D. C. Bradley and T. D. Anthopoulos, Adv Funct Mater 21 (2), 356–363 (2011).

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11:45 High Resolution KPFM investigations of nanoscale phase segregated organic bulk heterojunctionsAuthors : E. J. Spadafora* (a), R. Demadrille (a), B. Ratier (b), and B. Grévin (a) (a) UMR 5819SPrAM CEA-CNRS Université Joseph Fourier, Grenoble, France (b) XLIM UMR 6172 UniversityLimoges/CNRS, Limoges, FranceResume : A comprehensive high resolution Kelvin probe force microscopy (KPFM) investigationwas performed on the active layer of an organic solar cell (OSC), a 100 nm bulk hetero-junction(BHJ) blend of poly(3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM).This P3HT/PCBM blend has been optimized for use as an OSC with an overall power conversionefficiency of 4.25%. Chemical phase separation of the P3HT clusters is shown to be on the orderof the exciton diffusion length, ~10 nm. KPFM measurements were performed in dark and underillumination at 532 nm. Local surface contact potential measurements are recorded with aresolution of a few nm. In dark, a clear contrast (~100 mV) of the local surface potential betweenP3HT and PCBM is seen. However, under illumination, there is a global negative shift of the localsurface potential and the difference between P3HT and PCBM is significantly reduced.Furthermore, analysis of the surface photovoltage, obtained from contact potential images,reveals a spatial resolution of the space charge region, where exciton dissociation takes place, atthe donor/acceptor interfaces to be no more than ~3 nm. The resolution achieved in this workdemonstrates that electrical properties can be directly visualized in highly efficient organic BHJblends at the true nanometer scale by KPFM. In addition, new results on OSC's composed ofnovel BHJ blends will also be presented. (1) E. J. Spadafora et al. Nano Letters 2010, 10 (9),3337-3342

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12:00 Temperature-Dependent Selective Dissolution – New Ways to Determine Organic BulkHeterojunction MorphologiesAuthors : Bettina Friedel*, Bruno Ehrler, Neil C. Greenham; Cavendish Laboratory, University ofCambridge, JJ Thomson Avenue, CB30HE Cambridge, United KingdomResume : The morphology of the active layer in organic optoelectronic devices is vital to their

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function, particularly in bulk heterojunction systems for photovoltaics. Direct imaging of organicblends is often difficult due to the low contrast between the different carbon-based components.We present a new approach for the characterization of organic blends, based on a temperature-controlled selective dissolution technique. It allows one of the components to be selectivelyremoved from a bulk heterojunction, leaving a scaffold of the other component which can becharacterized much more easily, e.g. by high resolution scanning electron microscopy (SEM), dueto the higher air-material contrast. We demonstrate this technique on polymer/polymer andpolymer/small-molecule blends, and show that it can be used to study the effects of time andtemperature on phase separation. It also allows us to perform quantitative analysis of thefractions of ordered and disordered regions in the blend by simple optical absorptionspectroscopy. The technique is promising for future investigation of the effects of thermaltreatments and additives on the morphology and device performance of bulk heterojunctions.

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12:15 Bulk Hetero Junction Solar Cells: Shedding Light on the Morphology of Polymer-Fullerene BlendsAuthors : Alessandro Varotto* (Material Research Laboratory at University of California SantaBarbara and Mitsubishi Chemical Center for Advanced Materials) Fred Wudl (UCSB) Neil Treat(UCSB) Craig Hawker (UCSB) MIchael Chabinyc (UCSB)Resume : One of the challenges associated with solution processed bulk heterojunction solarcells is to understand the morphology of the donor/acceptor blend. The correct morphology andoptimal amount of solubility of the donor in the acceptor guarantee efficient charge separation atthe inter-phase followed by electron and hole collection. Recently, a model of interdiffusion ofPCBM and P3HT has been suggested but different systems such as lower band gap polymers andnovel fullerene derivatives are yet to be described. Herein we report on the next generation oflow symmetrical electron acceptors based on fullerene derivatives with tunable LUMO energylevel and solubility. We investigate on how changing the solubility of a family of fullerenes withidentical chemical and electronic properties affect the performance of the devices and themorphology of the films and shed light on the ratio between polymer and fullerene. Acombination of techniques such as D-SIMS, SEM and TEM correlates the morphology to theperformances.

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12:30 Lunch

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