MNT-301 UNIT-1-GGCT.pdf

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1

MNT-301

Unit-1

Prepared By Abhishek Sharma

abhishek_hbdyahoocom

Organic Semiconductors

Organic light emitting devices(OLEDs)

Self assembly of complex organic molecules

Molecular switches Thermochromic switches

Motor molecules

Bio-mimetic components

Charge transfer complexes

Molecular connections Contact issuesConducting polymers

Light emitting polymers

Polymerpolymer heterostructures

Plastic FETs

Organic Solar cells

Organic Photodiodes

Electronic paper Ink jet printing





2

Unit-1

bull Monomer A monomer (from Greek mono one and meros part) is a molecule that maybind chemically to other molecules to form a polymer

bull Polymer A polymer is a large molecule (macromolecule) composed of repeating

structural units These sub-units are typically connected by covalent chemical bonds

Although the term polymer is sometimes taken to refer to plastics

bull Oligomer An oligomer is a molecule that consists of a few monomer units (oligos is

Greek for a few) in contrast to a polymer that at least in principle consists of an

unlimited number of monomers

bull Natural polymeric materials such as shellac amber and natural rubber have been used

for centuries A variety of other natural polymers exist such as cellulose which is the main

constituent of wood and paper The list of synthetic polymers includes synthetic rubber

Bakelite neoprene nylon PVC polystyrene polyethylene polypropylene

polyacrylonitrile PVB silicone and many more

bull The preparation of plastics consists mainly of carbon atomsPrepared By Abhishek Sharma


11 Organic Semiconductor

bull 111 Introduction

bull Inorganic semiconductors like Si or Ge are as dominant material in electronics from the

before prevailing metals

bull Now at the beginning of the 21st century a new electronics revolution that has become

possible due to the development and understanding of a new class of materials commonly

known as Organic Semiconductors

bull There were several draw-backs preventing practical use of these early devices

bull Neither high enough current densities and light output nor sufficient stability could be

achieved

bull The main obstacles were the high operating voltage as a consequence of the crystal

thickness in the micrometre to millimetre range

bull The difficulties in scaling up crystal growth as well as preparing stable and sufficiently well-

injecting contacts to them





3

bull Applications such as large area flexible light sources and displays low-cost printed

integrated circuits or plastic solar cells from these materials

bull Organic semiconductors are not new

bull The first studies of the photoconductivity of anthracene crystals 20th century

bull Later on triggered by the discovery of electroluminescence in the 1960s

bull Molecular crystals were intensely investigated by many researchers

bull These investigations could establish the basic processes involved in optical excitation and

charge carrier transport

bull The 1970s the successful synthesis and controlled doping of conjugated polymers

established the second important class of organic semiconductors which was honoured

with the Nobel Prize in Chemistry in the year 2000

bull Together with organic photoconductors (molecularly doped polymers) these conducting

polymers have initiated the first applications of organic materials as conductive coatings or

photoreceptors in electrophotography



bull In 1980s the undoped organic semiconductors revived due to the demonstration of an

efficient photovoltaic cell incorporating an organic heterojunction of p- and n-conducting

materials as well as the first successful fabrication of thin film transistors from conjugated

polymers and oligomers

bull High-performance electroluminescent diodes from vacuum-evaporated molecular films

bull Organic light-emitting devices (OLEDs) have progressed rapidly and meanwhile lead to first

commercial products incorporating OLED displays

bull Other applications of organic semiconductors eg as logic circuits with organic field-effect

transistors (OFETs) or organic photovoltaic cells (OPVCs) are expected to follow in the

near future





4

bull 112 Types of Organic Semiconductors

bull Two major classes of organic semiconductors low molecular weight materials and polymers

bull An important difference between the two classes of materials lies in the way how they are

processed to form thin films

bull Whereas small molecules are usually deposited from the gas phase by sublimation or

evaporation

bull polymers can only be processed from solution eg by spin-coating or printing techniques

bull Both have in common a

conjugated π-electron system

being formed by the pz-orbitals of

sp2-hybridized C-atoms in the

molecules



bull As compared to the σ-bonds forming the backbone of the molecules the π-bonding is

significantly weaker

bull Therefore the lowest electronic excitations of conjugated molecules are the π-

πtransitions with an energy gap typically between 15 and 3 eV leading to light absorption

or emission in the visible spectral range

bull Table 1 The family of the

polyacenes The energy gap

can be controlled by the

degree of conjugation in a

molecule Thus chemistry

offers a wide range of

possibilities to tune the

optoelectronic properties of

organic semiconducting

materials





5

bull Some prototype materials that can be used for optoelectronic applications are



Basic Properties of Organic Semiconductors

bull 113 Basic Properties of Organic Semiconductors

bull Organic molecular crystals are van der Waals bonded solids implying a considerably

weaker intermolecular bonding as compared to covalently bonded semiconductors like Si or

GaAs

bull Consequences are seen in mechanical and thermodynamic properties like reduced

hardness or lower melting point

bull But much weaker delocalization of electronic wavefunctions among neighbouring

molecules which has direct implications for optical properties and charge carrier transport

bull But in case of Polymers

bull The morphology of polymer chains can lead to improved mechanical properties

bull Nevertheless the electronic interaction between adjacent chains is usually also quite weak

in this class of materials





6

bull 1131 Optical Poperties

bull The weak electronic delocalization to first order the optical absorption and luminescence

spectra of organic molecular solids are very similar to the spectra in the gas phase or in

solution

bull In particular intramolecular vibrations play an important role in solid state spectra and often

these vibronic modes can be resolved even at room temperature

bull Due to the crystal structure

or the packing of polymer

chains a pronounced

anisotropy can be found

bull Additionally disordered

organic solids usually showa considerable spectral

broadening


abhishek _hbdyahoocom





7



bull As a consequence of this weak electronic delocalization organic semiconductors have two

important peculiarities as compared to their inorganic counterparts

bull One is the existence of well-defined spin states (singlet and triplet) like in isolated

molecules which has important consequences for the photophysics of these materials (see

Fig 4)

bull However since intersystem crossing is a weak process this also sets an upper limit for the

electroluminescence quantum efficiency in OLEDs

bull A second important difference originates from the fact that optical excitations (ldquoexcitonsrdquo)

are usually localized on one molecule and therefore have a considerable binding energy of

typically 05 to 1 eV

bull Thus in a photovoltaic cells this binding energy has to be overcome before a pair of

independent positive and negative charge carriers is generated (see Fig 5)





8

bull 1132 Charge Carrier Transport

bull Transport of electrons or holes in an organic molecular solid is based on ionic molecular

states

bull (In order to create a hole an electron has to be removed to form a radical cation M+ out of

a neutral molecule M This defect electron can then move from one molecule to the next

In the same way electron transport involves negatively charged radical ions M-

bull (Qualitatively the same arguments hold for polymers however in this case charged states

are usually termed positive or negative polarons)



bull From this picture one can clearly see that due to the already mentioned exciton binding

energy the optical gap between the ground state and the first excited singlet state is

considerably less than the single particle gap to create an uncorrelated electron-hole pair





9

In going from molecular crystals to disordered organic solids one also has to consider locally

varying polarization energies due to different molecular environments which lead to a

Gaussian density of states for the distribution of transport sites as shown in Fig 7



bull Depending on the degree of order the charge carrier transport mechanism in organic

semiconductors can fall between two extreme cases

bull Band or Hopping transport

bull Band transport is typically observed in highly purified molecular crystals at not too high

temperatures

bull However electronic delocalization is weak the bandwidth is only small as compared to

inorganic semiconductors

bull At room temperature mobilities in molecular crystals reach only values in the range 1 to 10

cm2Vs

bull The band transport is the temperature dependence given by

bull μ α T-n

with n = 1 2 3helliphellip

bull Disordered materials (Amorphous) for example polymers are based on hopping transport

bull Hopping transport have much lower mobility values (10 ndash3 cm2Vs) in many cases is much less

bull The mobility is depends on the applied electric field

bull The mobility strongly depends on the degree of order and purity in organic

semiconductors and therefore to a great deal on the preparation and growth

conditions Prepared By Abhishek Sharma




10

bull At macroscopic level the current through a material is given by the charge carrier density

(n) and the carrier drift velocity (v) mobility (μ) and the electric field (F)



bull Charge Current Density

bull charge carrier density (n) the intrinsic carrier density in a semiconductor with an energy

gap (Eg) and an effective density of states N0

bull Taking typical values for an organic semiconductor with Eg= 25 eV and N0=1021 cm ndash3

leads to a hypothetical carrier density of ni=1 cm ndash3 at room temperature

bull (Nevertheless the corresponding value for Si (Eg= 112 eV and N0=1019 cm ndash3) is with

ni=1010 cm ndash3 many orders of magnitude higher)

bull In order to overcome the limitations posed by the low intrinsic carrier density different

means to increase the carrier density in organic semiconductors can be applied

bull 1 (electro-)chemical doping

bull 2 carrier injection from contacts

bull 3 photo-generation of carriers and

bull 4 field-effect doping



Self Assembly in Polymers

bull Several amphiphilic substances also form ordered layers on solid substrates

bull Requirement for such behavior is an adsorption of these molecules onto the surface an

intramolecular mobility and intermolecular stabilizing interactions

bull Typical examples are the n-aliphatic tail-groups with medium chain length (8-30 carbon

atoms) connected to a hydrophilic polar or easily polarizable head group that can react

with the substrate surface and with end-groups that do not react with the substrate

bull In the case of head-groups bound on the surface in a high density the end-groups

stabilize each other by van der Waals interactions So a cooperative effect of layer

stabilization can be observed which results in two-dimensional highly ordered monolayers

bull These arrangements are denoted as self-assembled monolayers (SAM)





11

bull The self-assembly of amphiphilic ionichydrophobic block copolymers generally takes

place in dilute solution

bull Block copolymers with both strongly and weakly dissociating (pH-sensitive) ionic

blocks are considered

bull We focus mostly on structural and morphological transitions that occur in self-

assembled aggregates as a response to varied environmental conditions (ionic

strength and pH in the solution)

bull The assembly of amphiphilic (macro) molecules in aqueous environments is a generic

mechanism of self-organization

bull means the spontaneous formation of self assembled structures of phospholipids and

biomacromolecules (it is the outcome of a delicate balance between attractive and

repulsive forces among which hydrophobic attraction hydrogen bonding metal-

coordination forces and steric or electrostatic repulsion play dominant roles)



bull Applications include (1) precise control over the size (on nanometer length scale) and

morphology of the assembled aggregates and (2) pronounced stimuli-responsive

properties

bull These structures can change their size total number etc in a significant way when the

physical andor chemical properties of the surroundings (temperature pH ionic

strength etc) are varied smoothly or that the structures recognize weak specific

stimuli such as trace concentrations of biologically active or toxic molecules

bull Structures formed by amphiphilic block copolymers composed of a hydrophilic block with

ionic and in particular pH-sensitive (weak polyelectrolyte) segments linked to a

hydrophobic block are more responsive This is because the strength of repulsive Coulomb

interactions between the polyelectrolyte (PE) segments can be efficiently tuned by variations

in pH orand ionic strength in the aqueous solution





12


bull According to electrical properties materials can be divided into four-types

bull insulator semiconductor conductor and superconductor

bull In general a material with a conductivity less than 10-7 Scm is regarded as an insulator

bull A material with conductivity larger than 103 Scm is called as a metal

bull The conductivity of a semiconductor is in a range of 10-4 ndash 10 Scm depending upon doping

degree Organic polymers usually are described by σ (sigma) bonds and π bonds The π-π

bonds are fixed and immobile due to forming the covalent bonds between the carbon

atoms On the other hand the σ-electrons in a conjugated polymers are relatively localised

unlike the σ electrons

bull Conductive polyacelene (PA) doped with iodine is a new field of conducting polymers

which is also called as ldquosynthetic metalsrdquo



bull Principle

bull a polymer has to imitate a metal which means that electrons in polymers need to be free

to move and not bound to the atoms

bull an oxidation or reduction process is often accompanied with adding or withdrawing of

electrons suggesting an electron can be removed from a material through oxidation or

introduced into a material through reduction

bull In 1977 Alan G MacDiarmidthey accidentally discovered that insulating π conjugated PA

could become conductor with a conductivity of 103

Scm by iodine doping

bull Materials

bull scientists thought that PA (Poly Acetylene) could be regarded as an excellent candidate of

polymers to be imitating a metal





13

bull Since discovery of conductive PA by iodine

doping [1] other π-conjugated polymers such

as polypyrrole (PPy) polyaniline (PANI)

polythiophenes(PTH) poly( p-

phenylene)(PPP) poly( p-

phenylenevinylene)(PPV) and poly(25-

thienylenevinylene)(PTV) have been reported

as conducting polymers

bull Usually the ground states of conjugated polymers are divided into degenerate and non-

degenerate

bull The prototype of degenerate polymers is trans-polyacetylene which has alternating C-C

and C=C bonds as shown The total energy curve of trans-polyacetylene has two equal

minima where the alternating C-C and C=C bonds are reversed

bull On the other hand a non-degenerate polymer has no two identical structures in the ground

state Most conjugated polymers such as PPy and PANI belong to non-degenerate

bull The band gaps of conjugated polymers are estimated to be typically in the range between 1

and 3 eV from their electronic absorption spectra These observations are consistent with

their insulator or semiconductor electrical propertiesPrepared By Abhishek Sharma


Molecular Switches

bull The principle of nano switch is the molecular movements that are linked to electronic

processes and on the other hand electronic transfers lead to at least temporarily changes

in the chemical structure

bull Nanoswitching processes are not limited to tunneling effects or single molecular processes

bull Because the nanomorphology of complex materials provides possibilities for nanoelectronic

switching

bull Example The use of the spontaneous spatial organization of domains in block-polymers

with a sequence of electron-conductive sections to control the electrical conductivity

bull Mixtures of pentadecylphenol with polystyrene-poly-p-vinylpyridine block-copolymer that has

been protonated with methylsulfonic acid exhibits thermally controlled electrical conductivity

bull This effect is caused by molecular reorientation processes from a lamellar domain structure

with character istic dimensions of 35nm and 5nm at 100oC over a non-lamellared block

structure (with increased conductivity) into a matrix structure with integrated columns with

distances of about 28nm at 150oC





14

bull A molecular switch is a nanoscale machine which switches reversibly between two or more states

bull Types of Molecular Switches

bull 1 Photochromic molecular switches

which are able to switch between

electronic configurations when

irradiated by light of a specific

wavelength Each state has a specific

absorption maximum which can then

be read out by UV-VIS spectroscopy

bull Members of this class include

azobenzenes diarylethenes

dithienylethenes fulgides stilbenes

spiropyrans and phenoxynaphthacenequinones

bull 2 Chiroptical molecular switches

bull are a specific subgroup with

photochemical switching taking place

between an enantiomeric pairs

bull In these compounds the readout is by

circular dichroism rather than by

ordinary spectroscopy

bull Hindered alkenes are used



Motor molecules

bull In general terms a motor may be defined as a device that consumes energy in one form

and converts it into motion or mechanical work

bull Molecular motors are biological molecular machines that are the essential agents of

movement in living organisms

bull Many protein based molecular motors harness the chemical free energy released by the

hydrolysis () of ATP in order to perform mechanical work

bull (ATP) adenosine-5-triphosphate

bull In terms of energetic efficiency this type of motor can be superior to currently available

man-made motors

bull One important difference between molecular motors and macroscopic motors is that

molecular motors operate in the thermal bath an environment in which the fluctuations

due to thermal noise are significant





15

bull A molecular motor is a protein that uses the energy of hydrolysis of a small molecule such

as a nucleoside triphosphate (NTP) to complete an enzymatic cycle during the course of

which the protein performs directional motion

bull Molecular motors are therefore unusual machines that accomplish what man-made devices

are unable to do the direct and isothermal conversion of chemical energy into mechanical

energy without the need to rely on an intermediate energy carrier heat or electricity

bull Synthetic Molecular Motor

bull Synthetic molecular motors are molecular machines capable of rotation under energy input

bull The term molecular motor has traditionally referred to a naturally occurring protein that

induces motion (via protein dynamics) some groups also use the term when referring to

non-biological non-peptide synthetic motors



Conducting Polymers

bull Conjugated polymers are intrinsic semiconductors whose conductivity increases through doping

This doping can be achieved by either chemical or electrical methods

Polypyrole





16

bull Synthesis

bull Polymer chains may be doped chemically through oxidation - primarily when an atom with

high electron affinity such as iodine or oxygen is present

bull Oxidation of the chain results in the formation of a polaron which is a radical cation

associated with lattice distortion (Figure 12)

bull Upon further doping an additional electron can be removed from either the polaron to form

a bipolaron or from elsewhere on the chain to form two polarons



bull Polythiophenes are a very good example of this class of compounds In addition to offering

high conductivity upon doping they have the added benefit of being relatively

environmentally and thermally stable

bull Unsubstituted polythiophene has good thermal stability and moderate conductivity after

doping with iodine however the resulting polymers are insoluble and not melt-processable

bull The conductivity of such polymers is the result of several processes Eg in traditional

polymers such as polyethylenes the valence electrons are bound in sp3 hybridized

covalent bonds

bull Such sigma-bonding electrons have low mobility and do not contribute to the electrical

conductivity of the material

bull However in conjugated materials the situation is completely different

bull Conducting polymers have backbones of contiguous sp2 hybridized carbon centers

bull One valence electron on each center resides in a pz orbital which is orthogonal to the other

three sigma-bonds

bull The electrons in these delocalized orbitals have high mobility when the material is doped

by oxidation which removes some of these delocalized electronsPrepared By Abhishek Sharma




17

bull Limitations The manufacturing costs material inconsistencies toxicity poor solubility in

solvents and inability to directly melt process

bull Applications

bull organic solar cells printing electronic circuits organic light-emitting diodes actuators

electrochromism supercapacitors chemical sensors and biosensors



Light emitting Polymer

bull The discovery of electroluminescence in poly( para-phenylene vinylene) (PPV) (Burroughes

et al 1990) has led to a re-awakened interest in conjugated polymers

bull These technologies include cheap and flexible light emitting displays photovoltaic devices

optical switching and field-effect transistors

bull We now turn to a description of the optical properties Figures 1 and 2 show the

characteristic linear absorption spectrum of the phenyl-based light emitting polymers





18

Polymer-polymer heterostructures







19

Organic Light Emitting Diode

bull An OLED (organic light-emitting diode) is a light-emitting diode (LED) in which the emissive

electroluminescent layer is a film of organic compound which emits light in response to anelectric current

bull This layer of organic semiconductor material is situated between two electrodes

bull Generally at least one of these electrodes is transparent

bull Materials Polyparaphenylenevinylene exhibits a high electrical conductivity and is used as

a material for organic light emitting diodes (lsquoOLEDsrsquo)

bull Construction By integration of electrically conductive polymers such as substituted

polythiophenes in a nanoporous membrane and wiring by a metal base electrode and at

least a partially transparent membrane electrode organic light diodes have been

constructed

bull They generate photons via the field-based emission of electrons from a cathode which are

then accelerated over a short distance onto a luminescent material

bull To achieve large electrical field strength (about 03 V nm) with moderate voltages the gaps

between the cathode and counter electrodes should be as small as possible



bull HTL hole transport layer

bull ETL electron transport layer

bull EML emission layer

bull Alq3

bull Current scaling with the 3rd power of the

reciprocal thickness

bull Instead of the displayed combination of a

triphenylamine derivative and Alq3

polymeric OLEDs usually employ a

conductive polymer

bull (PEDOTPSS) together with luminescent

polymers like PPV or PFO derivatives

bull Injection of charge carriers from contacts plays important role for the operation of organic

light-emitting devices (OLEDs)

bull This requires low energetic barriers at the metal-organic interfaces for both contacts to

inject equally high amounts of electrons and holes

bull Relatively high electric fields being applied to OLEDs (typically 5 to 10 V across a layer

thickness of 100 nm yield F = 051MVcm) low mobility materialsAlq3





20

bull In organic semiconductors large fraction of the excited states formed by charge carrier

recombination are triplets

bull The most efficient OLEDs nowadays make use of energy transfer to so-called tripletemitters where the presence of heavy metals renders the transition from the triplet state to

the ground state via phosphorescence an allowed process



Organic Photo Detector or Diode

bull OPDs the device was fabricated onto an ITO coated glass substrate by OMBD (Organic

molecular beam deeposition) at a background pressure of 10minus5 Pa

bull The device consists of the heterostructure of copper phthalocyanine (CuPc) and N N prime-bis(25-

di-tert -butylphenyl) 34910-perylenedicarboximide (BPPC) as a p-type and an n-type material

respectively

bull CuPc fi lm has high sensitivity and stability in air and it shows a strong absorption band at the

wavelength range of 550ndash780 nm whereas BPPC shows an absorption band in the range of

400ndash550 nm

bull The thickness of CuPc layer was set at 30 nm which corresponds to the exciton diffusion

length in the photogenerated layer

bull As an electrode 30 nm thick Au was deposited on the BPPC layer

bull The device was covered by a glass plate in Ar gas atmosphere to prevent oxidation of the

organic layers

bull The active area of the device was fixed at 001 mm2 in order to reduce the influence of the RC

time constant Prepared By Abhishek Sharma




21

bull For devices fabricated by solution process poly(99-dioctylfl uorene) and a phosphorescent

iridium derivative (iridium (III) bis(2-(46-difl uorophenyl) pyridinato-NC2) (FIrpic) or iridium

(III) bis(2-(2prime-benzothienyl) pyridinato-NC3prime) (acetylacetonate) (btp2Ir(acac)) were used as ahost and a dopant material respectively

bull The materials were dissolved in 124-trichlorobenzene or chloroform solution and the organic

layers were fabricated by spin coating The active area of the device was fixed at 003 mm2

The device structure and the materials used in the experiments are shown in Figure 154a and

b for vacuum and solution processed devices respectively







22

Organic Solar cell (Plastic Solar Cell or

Polymer Solar Cell)bull An organic solar cell or plastic solar cell is a type of polymer solar cell that uses organic

electronics

bull It deals with conductive organic polymers or small organic molecules for light absorption

and charge transport to produce electricity from sunlight by the photovoltaic effect

bull The optical absorption coefficient of organic molecules is high so a large amount of light

can be absorbed with a small amount of materials

bull These cells are made by sandwiching a layer of organic electronic materials between two

metallic conductors

bull The difference of work function between the two

conductors sets up an electric field in the organic

layer

bull When the organic layer absorbs light electrons will

be excited to the Lowest Unoccupied Molecular

Orbital (LUMO) and leave holes in the Highest

Occupied Molecular Orbital (HOMO) forming

excitons Prepared By Abhishek Sharma


bull this can be overcome by making use of a

photoinduced charge transfer between an

electron donor like PPVand the fullerene

C60 as an acceptor

bull Bulk heterojunction devices usually

consist of a mixture of soluble PPV (or

P3AT) and fullerene derivatives

bull Alternatively mixed layers of evaporated

small molecules like CuPc and C60 can

be used

bull Materials

bull Bulk heterojunction devices usually consist of a mixture of soluble PPV (or P3AT) and

fullerene derivatives

bull Structure Alternatively mixed layers of evaporated small molecules like CuPc

(Polycarbonate) and C60 can be used

bull Other than organic material previously used materials has the high absorption coefficient

(105 cm-1) than organic semiconductors Organic semiconductors faces some problem of

the high binding energy





23

bull Due to the short exciton diffusion length of typically 10 nm only efficient OPVCs use the

so-called bulk-heterojunction concept of mixing donor and acceptor in one single layer

bull In spite of the huge progress recently achieved there are still challenges to achieve

sufficient lifetime of OPVCs under ambient conditions or the availability of low-band gap

materials to make better use of the solar spectrum



Organic Field effect transistor or plastic FETs

bull An organic field-effect transistor (OFET) is a field effect transistor using an organic

semiconductor in its channel

bull OFETs can be prepared either by vacuum evaporation of small molecules by solution-

casting of polymers or small molecules or by mechanical transfer of a peeled single-

crystalline organic layer onto a substrate These devices have been developed to realize

low-cost large-area electronic products and biodegradable electronics

bull The most commonly used device geometry is bottom gate with top drain- and sourceelectrodes because this geometry is similar to the thin-film silicon transistor (TFT) using

thermally grown SiSiO2 oxide as gate dielectric

bull Organic polymers such as poly(methyl-methacrylate) (PMMA) can also be used as

dielectric





bull Materials

bull One common feature of OFET materials is the inclusion of an aromatic or otherwise

conjugated π-electron system facilitating the delocalization of orbital wavefunctions

bull Electron withdrawing groups or donating groups can be attached that facilitate hole or

electron transport OFETs employing many aromatic and conjugated materials as the

active semiconducting layer have been reported including small molecules such as

rubrene tetracene pentacene di indenoperylene perylenediimides

tetracyanoquinodimethane (TCNQ) and polymers such as polythiophenes (especially poly

3-hexylthiophene (P3HT)) polyfluorene polydiacetylene poly 25-thienylene vinylene poly

p-phenylene vinylene (PPV)

bull Rubrene-based OFETs show the highest carrier mobility 20ndash40 cm2(V983223s)

bull pentacene-based OFETs reported 10 times lower mobilities than rubrene

bull Polycrystalline tetrathiafulvalene and its analogues result in mobilities in the range 01ndash

14 cm2(V983223s)

bull The mobility exceeds 10 cm2(V983223s) in solution-grown or vapor-transport-grown single

crystalline hexamethylene-tetrathiafulvalene (HMTTF)Prepared By Abhishek Sharma


bull Design

bull Three essential components of field-effect transistors are the source the drain and the gate

Field-effect transistors usually operate as a capacitor

bull They are composed of two plates One plate works as a conducting channel between two

ohmic contacts which are called the source and the drain contacts

bull The other plate works to control the charge induced into the channel and it is called the gate

bull The direction of the movement of the carriers in the channel is from the source to the drain

bull Hence the relationship between these three components is that the gate controls the carrier movement from the source to the drain

bull When this capacitor concept is applied to the device design various devices can be built up

based on the difference in the controller - ie the gate





2

Unit-1

bull Monomer A monomer (from Greek mono one and meros part) is a molecule that maybind chemically to other molecules to form a polymer

bull Polymer A polymer is a large molecule (macromolecule) composed of repeating

structural units These sub-units are typically connected by covalent chemical bonds

Although the term polymer is sometimes taken to refer to plastics

bull Oligomer An oligomer is a molecule that consists of a few monomer units (oligos is

Greek for a few) in contrast to a polymer that at least in principle consists of an

unlimited number of monomers

bull Natural polymeric materials such as shellac amber and natural rubber have been used

for centuries A variety of other natural polymers exist such as cellulose which is the main

constituent of wood and paper The list of synthetic polymers includes synthetic rubber

Bakelite neoprene nylon PVC polystyrene polyethylene polypropylene

polyacrylonitrile PVB silicone and many more

bull The preparation of plastics consists mainly of carbon atomsPrepared By Abhishek Sharma


11 Organic Semiconductor

bull 111 Introduction

bull Inorganic semiconductors like Si or Ge are as dominant material in electronics from the

before prevailing metals

bull Now at the beginning of the 21st century a new electronics revolution that has become

possible due to the development and understanding of a new class of materials commonly

known as Organic Semiconductors

bull There were several draw-backs preventing practical use of these early devices

bull Neither high enough current densities and light output nor sufficient stability could be

achieved

bull The main obstacles were the high operating voltage as a consequence of the crystal

thickness in the micrometre to millimetre range

bull The difficulties in scaling up crystal growth as well as preparing stable and sufficiently well-

injecting contacts to them





3


























near future





4






evaporation






molecules

















materials





5








GaAs













6




solution





chains a pronounced




broadening







7







Fig 4)












8



states















9










temperatures




cm2Vs


bull μ α T-n











10



































11


















properties














12















bull Principle









bull Materials







13










degenerate










Molecular Switches






switching













14
























Motor molecules









man-made motors








15














Conducting Polymers



Polypyrole





16

bull Synthesis
















covalent bonds






three sigma-bonds






17



bull Applications
















18








19











constructed










bull Alq3






conductive polymer













20












respectively



400ndash550 nm





organic layers






21














22



electronics






metallic conductors



layer










C60 as an acceptor






be used

bull Materials












23


















dielectric





bull Materials













14 cm2(V983223s)




bull Design














3


























near future





4






evaporation






molecules

















materials





5








GaAs













6




solution





chains a pronounced




broadening







7







Fig 4)












8



states















9










temperatures




cm2Vs


bull μ α T-n











10



































11


















properties














12















bull Principle









bull Materials







13










degenerate










Molecular Switches






switching













14
























Motor molecules









man-made motors








15














Conducting Polymers



Polypyrole





16

bull Synthesis
















covalent bonds






three sigma-bonds






17



bull Applications
















18








19











constructed










bull Alq3






conductive polymer













20












respectively



400ndash550 nm





organic layers






21














22



electronics






metallic conductors



layer










C60 as an acceptor






be used

bull Materials












23


















dielectric





bull Materials













14 cm2(V983223s)




bull Design














4






evaporation






molecules

















materials





5








GaAs













6




solution





chains a pronounced




broadening







7







Fig 4)












8



states















9










temperatures




cm2Vs


bull μ α T-n











10



































11


















properties














12















bull Principle









bull Materials







13










degenerate










Molecular Switches






switching













14
























Motor molecules









man-made motors








15














Conducting Polymers



Polypyrole





16

bull Synthesis
















covalent bonds






three sigma-bonds






17



bull Applications
















18








19











constructed










bull Alq3






conductive polymer













20












respectively



400ndash550 nm





organic layers






21














22



electronics






metallic conductors



layer










C60 as an acceptor






be used

bull Materials












23


















dielectric





bull Materials













14 cm2(V983223s)




bull Design














5








GaAs













6




solution





chains a pronounced




broadening







7







Fig 4)












8



states















9










temperatures




cm2Vs


bull μ α T-n











10



































11


















properties














12















bull Principle









bull Materials







13










degenerate










Molecular Switches






switching













14
























Motor molecules









man-made motors








15














Conducting Polymers



Polypyrole





16

bull Synthesis
















covalent bonds






three sigma-bonds






17



bull Applications
















18








19











constructed










bull Alq3






conductive polymer













20












respectively



400ndash550 nm





organic layers






21














22



electronics






metallic conductors



layer










C60 as an acceptor






be used

bull Materials












23


















dielectric





bull Materials













14 cm2(V983223s)




bull Design














6




solution





chains a pronounced




broadening







7







Fig 4)












8



states















9










temperatures




cm2Vs


bull μ α T-n











10



































11


















properties














12















bull Principle









bull Materials







13










degenerate










Molecular Switches






switching













14
























Motor molecules









man-made motors








15














Conducting Polymers



Polypyrole





16

bull Synthesis
















covalent bonds






three sigma-bonds






17



bull Applications
















18








19











constructed










bull Alq3






conductive polymer













20












respectively



400ndash550 nm





organic layers






21














22



electronics






metallic conductors



layer










C60 as an acceptor






be used

bull Materials












23


















dielectric





bull Materials













14 cm2(V983223s)




bull Design














7







Fig 4)












8



states















9










temperatures




cm2Vs


bull μ α T-n











10



































11


















properties














12















bull Principle









bull Materials







13










degenerate










Molecular Switches






switching













14
























Motor molecules









man-made motors








15














Conducting Polymers



Polypyrole





16

bull Synthesis
















covalent bonds






three sigma-bonds






17



bull Applications
















18








19











constructed










bull Alq3






conductive polymer













20












respectively



400ndash550 nm





organic layers






21














22



electronics






metallic conductors



layer










C60 as an acceptor






be used

bull Materials












23


















dielectric





bull Materials













14 cm2(V983223s)




bull Design














8



states















9










temperatures




cm2Vs


bull μ α T-n











10



































11


















properties














12















bull Principle









bull Materials







13










degenerate










Molecular Switches






switching













14
























Motor molecules









man-made motors








15














Conducting Polymers



Polypyrole





16

bull Synthesis
















covalent bonds






three sigma-bonds






17



bull Applications
















18








19











constructed










bull Alq3






conductive polymer













20












respectively



400ndash550 nm





organic layers






21














22



electronics






metallic conductors



layer










C60 as an acceptor






be used

bull Materials












23


















dielectric





bull Materials













14 cm2(V983223s)




bull Design














9










temperatures




cm2Vs


bull μ α T-n











10



































11


















properties














12















bull Principle









bull Materials







13










degenerate










Molecular Switches






switching













14
























Motor molecules









man-made motors








15














Conducting Polymers



Polypyrole





16

bull Synthesis
















covalent bonds






three sigma-bonds






17



bull Applications
















18








19











constructed










bull Alq3






conductive polymer













20












respectively



400ndash550 nm





organic layers






21














22



electronics






metallic conductors



layer










C60 as an acceptor






be used

bull Materials












23


















dielectric





bull Materials













14 cm2(V983223s)




bull Design














10



































11


















properties














12















bull Principle









bull Materials







13










degenerate










Molecular Switches






switching













14
























Motor molecules









man-made motors








15














Conducting Polymers



Polypyrole





16

bull Synthesis
















covalent bonds






three sigma-bonds






17



bull Applications
















18








19











constructed










bull Alq3






conductive polymer













20












respectively



400ndash550 nm





organic layers






21














22



electronics






metallic conductors



layer










C60 as an acceptor






be used

bull Materials












23


















dielectric





bull Materials













14 cm2(V983223s)




bull Design














11


















properties














12















bull Principle









bull Materials







13










degenerate










Molecular Switches






switching













14
























Motor molecules









man-made motors








15














Conducting Polymers



Polypyrole





16

bull Synthesis
















covalent bonds






three sigma-bonds






17



bull Applications
















18








19











constructed










bull Alq3






conductive polymer













20












respectively



400ndash550 nm





organic layers






21














22



electronics






metallic conductors



layer










C60 as an acceptor






be used

bull Materials












23


















dielectric





bull Materials













14 cm2(V983223s)




bull Design














12















bull Principle









bull Materials







13










degenerate










Molecular Switches






switching













14
























Motor molecules









man-made motors








15














Conducting Polymers



Polypyrole





16

bull Synthesis
















covalent bonds






three sigma-bonds






17



bull Applications
















18








19











constructed










bull Alq3






conductive polymer













20












respectively



400ndash550 nm





organic layers






21














22



electronics






metallic conductors



layer










C60 as an acceptor






be used

bull Materials












23


















dielectric





bull Materials













14 cm2(V983223s)




bull Design














13










degenerate










Molecular Switches






switching













14
























Motor molecules









man-made motors








15














Conducting Polymers



Polypyrole





16

bull Synthesis
















covalent bonds






three sigma-bonds






17



bull Applications
















18








19











constructed










bull Alq3






conductive polymer













20












respectively



400ndash550 nm





organic layers






21














22



electronics






metallic conductors



layer










C60 as an acceptor






be used

bull Materials












23


















dielectric





bull Materials













14 cm2(V983223s)




bull Design














14
























Motor molecules









man-made motors








15














Conducting Polymers



Polypyrole





16

bull Synthesis
















covalent bonds






three sigma-bonds






17



bull Applications
















18








19











constructed










bull Alq3






conductive polymer













20












respectively



400ndash550 nm





organic layers






21














22



electronics






metallic conductors



layer










C60 as an acceptor






be used

bull Materials












23


















dielectric





bull Materials













14 cm2(V983223s)




bull Design














15














Conducting Polymers



Polypyrole





16

bull Synthesis
















covalent bonds






three sigma-bonds






17



bull Applications
















18








19











constructed










bull Alq3






conductive polymer













20












respectively



400ndash550 nm





organic layers






21














22



electronics






metallic conductors



layer










C60 as an acceptor






be used

bull Materials












23


















dielectric





bull Materials













14 cm2(V983223s)




bull Design














16

bull Synthesis
















covalent bonds






three sigma-bonds






17



bull Applications
















18








19











constructed










bull Alq3






conductive polymer













20












respectively



400ndash550 nm





organic layers






21














22



electronics






metallic conductors



layer










C60 as an acceptor






be used

bull Materials












23


















dielectric





bull Materials













14 cm2(V983223s)




bull Design














17



bull Applications
















18








19











constructed










bull Alq3






conductive polymer













20












respectively



400ndash550 nm





organic layers






21














22



electronics






metallic conductors



layer










C60 as an acceptor






be used

bull Materials












23


















dielectric





bull Materials













14 cm2(V983223s)




bull Design














18








19











constructed










bull Alq3






conductive polymer













20












respectively



400ndash550 nm





organic layers






21














22



electronics






metallic conductors



layer










C60 as an acceptor






be used

bull Materials












23


















dielectric





bull Materials













14 cm2(V983223s)




bull Design














19











constructed










bull Alq3






conductive polymer













20












respectively



400ndash550 nm





organic layers






21














22



electronics






metallic conductors



layer










C60 as an acceptor






be used

bull Materials












23


















dielectric





bull Materials













14 cm2(V983223s)




bull Design














20












respectively



400ndash550 nm





organic layers






21














22



electronics






metallic conductors



layer










C60 as an acceptor






be used

bull Materials












23


















dielectric





bull Materials













14 cm2(V983223s)




bull Design














21














22



electronics






metallic conductors



layer










C60 as an acceptor






be used

bull Materials












23


















dielectric





bull Materials













14 cm2(V983223s)




bull Design














22



electronics






metallic conductors



layer










C60 as an acceptor






be used

bull Materials












23


















dielectric





bull Materials













14 cm2(V983223s)




bull Design














23


















dielectric





bull Materials













14 cm2(V983223s)




bull Design














bull Materials













14 cm2(V983223s)




bull Design












MNT-301 UNIT-1-GGCT.pdf

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Transcript of MNT-301 UNIT-1-GGCT.pdf