IEE/CEEM Seminar: P. Daniel Dapkus and Semiconductor Nanostructures in Energy Devices
IEE/CEEM Seminar: Materials for Organic Photovoltaics: Non-Fullerene Acceptors and Low-Band Gap Dyes...
description
Transcript of IEE/CEEM Seminar: Materials for Organic Photovoltaics: Non-Fullerene Acceptors and Low-Band Gap Dyes...
Materials for Organic Photovoltaics:Non-Fullerene Acceptors and Low-Band Gap Dyes
for Ternary BHJ OPVs"
Alan Sellinger!Colorado School of Mines, Chemistry Department!
!
Center for Energy Efficient Materials Seminar!University of California, Santa Barbara!
October 9, 2013!
Eight19 Limited
NNN
NN N NNSi
O
O
Si
Si
NO
O
NS
N
N
O
O
Founded in 1874 (http://www.mines.edu/)
Golden, CO (20 mi south of Boulder/15 mi west of Denver)
5600 students (1500 graduate students)
Ranked #40 public university (US News & World Report 2013)
13,000 applications for 950 spots in freshman class
Ranked #6 for highest average salary for grads (payscale.com)
$60M in external research grants (2012)
• Established in 1974 (www.nrel.gov) A DOE laboratory
• Golden, CO (3 miles from CSM)
• 1,700 fulltime employees, 800 visiting researchers, interns, and contractors
• 327 acre campus in Golden (300+ acre wind campus in Boulder)
• World leader in renewable energy R&D – Solar, Wind, Biomass, Hydrogen Technology, Geothermal, Water
• National Center for Photovoltaics, National Wind Technology Center
• Average annual budget past 5 years $430M
Organic Solar has Potential to be a Low Cost Source of Clean Energy"
Low-‐Cost Materials
Low-‐Cost Installa1on Low-‐Cost Manufacturing
Copper Phthalocyanine
(CuPc) NN
N
NN
NN
N
Cu
Organic solar cells are rapidly improving"
2000 2002 2004 2006 2008 2010 20122
3
4
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H elia tek
K ona rka
H elia tek
O rg anic T andem O rganic
Efficien
cy (%)
U nivers ity L inz
G roningen
S iemens
NR E L /K ona rka /Univ . L inz
P lex tronic s
K ona rka
S ola rmer
Univ . D res den
H elia tekS umitomoUC L A
Source: NREL
UCLA
12
2013
Heliatek
Polyera
Estimated lifetimes of OPVs
Burn-in loss Burn-in time
Lifetime in linear regime*
P3HT:PCBM 16% 55 days 3.5 years
PCDTBT:PC70BM 27% 38 days 6.7 years
*Lifetime assumes 5.5 hrs/day of one-sun intensity1
1. Peters, C. H.; Sachs-Quintana, I. T.; Kastrop, J. P.; Beaupre, S.; Leclerc, M.; McGehee, M. D.: Adv Ener Mater 2011, 1, 491-494.
• Heliatek (BASF and Bosch) has achieved 30 year lifetimes with tandem OPVs2
2. www.heliatek.com
A Fair Comparison of Efficiency"
• Cells are rated at 1 sun (calibrated light source), normal incidence and 25°C.
• Not really solar cell operating conditions
• OPV holds it performance better than Si at low light, low angles and high temperature.
• At “real” operating conditions, averaged over the year an OPV system may get 30% more power than a Si system with the same rating.
• 10% rated OPV cell may behave more like a 13% rated Si cell
OPV Precursor - Organic LEDs for Displays
Organic LEDs for Lighting
New Applications for Organic Solar Cells
SS
C6H13
SS
C6H13
C6H13
C6H13
n/4
Materials for Organic LED & PV:Combination of 3 Nobel Prizes!"
S
O O
nPEDOT
C60 C70
• 2000 Nobel Prize in Chemistry - Alan Heeger, Alan G. MacDiarmid, Hideki Shirakawa for their discovery and development of conductive polymers
• 2010 Nobel Prize in Chemistry - Richard F. Heck, Ei-ichi Negishi, Akira Suzuki for palladium-catalyzed cross couplings in organic synthesis
• C-C bond formation
• 1996 Nobel Prize in Chemistry - Robert F. Curl Jr., Sir Harold Kroto, Richard E. Smalley for their discovery of fullerenes (C60)
N
O
O
NS
N
N
O
O
Types of Materials for Organic Solar Cells
• p-type (electron donating materials)!– Aromatic amines, thiophenes!– ≈90% of journal publications related to p-type materials!
• n-type materials (electron accepting materials)!– Primarily fullerene derivatives!– Cyano aromatics, perylene diimides, benzothiadiazole!– Area relatively unexplored due to not-so-straightforward
chemistry!
Drawbacks for fullerenes"
Reduced solar spectrum absorption
300 400 500 600 700 8000
0.5
1
1.5
2
2.5 x 105
Wavelength (nm)
Abs
orpt
ion
Coe
ffici
ent (
M-1 c
m-1
)
New AcceptorPC60BMPC70BM
Lower VOC
-3.1 eV
-5.1 eV
P3HT
PCBM
-4.3 eV
-3.7 eV
-6.1 eV
-5.6 eV
-3.1 eV
-5.1 eV
P3HT -3.9 eV
-6.1 eV
New Acceptor
-3.4 eV
-5.9 eV
Difficult synthesis and purification = Higher cost PC60BM: $50/g
Fullerene acceptor – up to 10% of total PV system cost
Roes et al., Prog. Photovoltaics. 2009 (17) 372-393
Effect of Production Steps on Cost"
• Significant increases (2X) for higher purification!• PC71BM approximately 3.4X more expensive than PC61BM!
Anctil et al., Environ. Sci. Technol. 45, (2011) 2353-9
O
OO
O
PC60BM PC70BM
Fullerenes are large portion of module cost"
• Assumptions!– Module efficiency: 10%!– Thickness of active layer: 200 nm!– Volume fraction of acceptor material in active layer: 50%!– Fraction of PCBM wasted due to processing: 5%!– PCBM manufacturing cost (scaled-up estimate): $35-70/g!
• PC61BM cost per area - $5.40-$11.00 m-2!
• PC61BM cost per watt - $0.06-$0.12 W-1!
• Cost associated with separation, purification and functionalization of fullerenes is significant"
High-efficiency BHJ solar cells"
• Record OPV cells ALL use fullerene derivatives (PC70BM, ICBA)"• Recent development based on donor materials discovery"
p-DTS(FBTTh2)2:PC70 BM
7.8% PCE
He et al., Nature Phot. 2012, (6) 591-595 (Inverted Cell) Yong Cao Group South China University of Technology
PTB7:PC70BM 9.2% PCE
ICBA 10.6% PCE
(tandem cell)
You et al., Nature Comm. 2013, 4, 1446, doi:10.1038/ncomms2411 Yang Group, UCLA
Kyaw et al., Adv. Mater., 2013, 25, 2397–2402 All small molecule solution processed Bazan/Heeger Group, UCSB
New Acceptors based on Vinazene • Original applications as high nitrogen containing materials for
reduced flammability. Without vinyl groups has been used in the agriculture sector (fertilizers)
• Their highly electron deficient properties make them candidates as acceptor materials in organic electronic applications
Vinazene 2-vinyl-4,5-dicyanoimidazole 4,5-dicyanoimidazole
HN N
NC CN
HN N
NC CN
R
HN N
NC CN
R
Commercially available
Alkylation of 2-Vinyl-4,5-dicyanoimidazole "
NHN
NC CNVinazene
Acetone, K2CO3
Acetone, K2CO3
INN
NC CN1-Butylvinazene (90%)
NN
NC CN1-Hexylvinazene (90%)
NN
NC CN1-Ethylhexylvinazene (56%)
DMF, K2CO3, 70oC
Reflux
Reflux
I
Br
Tunable Synthesis: Heck Chemistry
Shin R.Y.C., Sonar, P., Siew, P.S., Chen, Z.C., Sellinger, A., J. Org. Chem., 2009, 74 (9), 3293–3298.
Optical properties of selected vinazene derivatives
300 350 400 450 500 550 600 6500.0
0.2
0.4
0.6
0.8
1.0
Nor
mal
ised
Inte
nsity
(a.u
.)
Wavelength (nm)
1 4 5 10 13
350 400 450 500 550 600 650 700 7500.0
0.2
0.4
0.6
0.8
1.0
Nor
mal
ised
Inte
nsity
(a.u
.)
Wavelength (nm)
1 4 5 10 13
UV spectra of the molecules in toluene
PL spectra of the molecules in toluene
Significant absorption in visible spectrum
(1)
NS
N
(4)
NS
N
S
S
(5)(10) (13)
Shin R.Y.C., Sonar, P., Siew, P.S., Chen, Z.C., Sellinger, A., J. Org. Chem., 2009, 74 (9), 3293–3298.
Vinazenes used for OPVs
HV-BT
EV-BT Better solubility
N
N
CN
CN
N
N
NC
NC
NS
N
Solubilizing groups for solution processing
Electron accepting sites
Conjugated chemical links
• Can be thermally sublimed as well
Preparation of OPV Devices"
New Electron Acceptor
Donor polymer
• Solution processed active layer
POPT with HV-BT
• Kietzke, T., Shin R.Y.C., Egbe, D.A.M., Chen, Z.K., and Sellinger, A., Macromolecules, 2007, 40, 4424-4428. • Shin R.Y.C., Kietzke, T., Sudhakar, S., Dodabalapur A., Chen, Z.K., and Sellinger, A., Chem. Mater., 2007, 19(8),
1892-1894. • Woo, C.W., Holcombe, T.W., Tam, T.L., Sellinger, A., Frechet, J.M.J., Chem. Mater. 2010, 22 (5), 1673–1679
Voc = 0.62 V, FF = 0.40, PCE = 1.41%
POPT
Can we make better acceptors?
N
N
CN
CN
N
N
NC
NC
NS
N
Solubilizing groups for solution processing
Electron accepting sites
Conjugated chemical links
• Corresponding electron donor has charge mobility (cm2/V sec) in 10-4 range. Is charge transport mis-match a problem?
Improving Organic Acceptor Materials"
Improved Acceptor Materials?"
NS
N
N
O
O
N
O
O
Acceptor Materials: Computational Studies"
Ground-state geometries
LUMO
HOMO
NS
N
NN
O
O
O
O
Computational studies done by Bredas group at Georgia Tech
Molecular Simulation – Ground State Geometry"
• Twisting of NI-BT molecule due to steric interactions may prevent crystallization in films?!
HPI-BT NI-BT
2.06
2.06 27.3°
Initial Synthetic Scheme for PI-BT/NI-BT"PI-BT
PI-BT
NI-BT
NI-BT
Improved Synthetic Scheme for PI-BT"
N
O
O
Br BF3K+PdCl2, PPh3, Cs2CO3
THF-H2O, 85° CN
O
O(94%)
NS
N
NN
O
O
O
ONS
N
BrBr
Pd[P(tBu)3]2, Cy2NMe
Toluene, 100° C
(81%)
N
O
O +
New Acceptor Properties"
• Larger ELUMO,Acc – EHOMO,Don than for P3HT:PC60BM!
200 300 400 500 600 700 800 9000
0.2
0.4
0.6
0.8
1
Wavelength (nm)
Nor
mal
ized
Abs
orpt
ion
(arb
. uni
ts.) PI-BT
NI-BT
Thin Film
-3.69 eV
-6.05 eV
-3.1 eV
-5.1 eV
-3.84 eV
-5.99 eV
-3.1 eV
-5.1 eV
P3HT
PI-BT NI-BT
P3HT
ΔELUMO ~ 0.6 eV ΔEHOMO ~ 0.9 eV
ΔELUMO ~ 0.7 eV ΔEHOMO ~ 0.9 eV
• Peak acceptor absorption is in visible spectrum!
• Tunable LUMO – expected higher Voc than fullerenes!
HPI-BT
Electron Mobility in HPI-BT"
• FET mobility measurements for PI-BT yield µe ~ 1–1.4 × 10-3 cm2/V-s!– PCBM µe,FET ~ 5–10 × 10-3 cm2/V-s!
• Could not measure a FET mobility for NI-BT!
Glass substrate
Al
LiF (1nm)
Al
LiF (1nm)
Cytop (Spin-on dielectric)
Al (Gate)
FET Configuration -20 0 20 40 60 80 100
10-10
10-9
10-8
10-7
I SD (A
)
-20 0 20 40 60 80 100
0.5
1
1.5
2
2.5
3
3.5x 10-8
Gate Voltage (V)
I SD (A
)
Courtesy of Scott Himmelberger from Prof. Alberto Salleo’s group in Stanford MSE
Initial Devices"
P3HT:HPI-BT
P3HT:NI-BT
Solvent Chlorobenzene Chloroform
Thickness (nm) ~ 90 ~ 120
Cathode LiF(1nm)/Al Ca(7nm)/Al
Anneal Pre/Post
Post Pre
Ann. Temp/Time
110°C/3min 110°C/10min
Jsc (mA/cm2) 4.7 1.2
Voc (V) 0.96 0.51
FF 0.56 0.35
PCE (%) 2.54 0.22
-1 -0.5 0 0.5 1 1.5-8
-6
-4
-2
0
2
4
6
8
Voltage (V)
Cur
rent
Den
sity
(mA
cm-2
)
PI-BTNI-BT
• High voltage as expected with higher-lying LUMO (0.96 V)!!• Why is the efficiency for NI-BT 10X lower?!
Bloking et al., Chem. Mater., 2011, V.23(24), p. 5484-90, DOI: 10.1021/cm203111k
High Efficiencies with Other Donor Polymers"
• Alternative polythiophene (PDHTT) with lower HOMO level boosts VOC up to 1.1 V and still has 3.4% efficiency and 64% FF!
• Non-planar NI-BT molecule – 0.2% PCE!• One of the highest Non-fullerene OPV to date"
BASF P3HT
PDHTT Rieke P3HT
Jsc (mA/cm2)
6.3 4.8 5.8
Voc (V) 0.95 1.11 0.97
FF 0.62 0.64 0.54
PCE (%) 3.72 3.41 3.03
-1 -0.5 0 0.5 1 1.5-10
-8
-6
-4
-2
0
2
4
6
8
10
Voltage (V)
Cur
rent
Den
sity
(mA/
cm2 )
PDHTTRieke P3HTBASF P3HT
Bloking et al., Chem. Mater., 2011, V.23(24), p. 5484-90, DOI: 10.1021/cm203111k Bloking et al., Adv. Energy Mater., submitted, 2013 Ko, S. W. Bao, Z. et al J Am Chem Soc. 2011, 133, 16722-16725. DOI: 10.1021/ja207429s
S
C6H13
n S
C6H13
SS
C6H13
n
Z. Bao, Stanford!
EQE Spectra of P3HT:HPI-BT Device"
• Significant photocurrent generation from acceptor absorption!
300 400 500 600 700 800 9000
0.1
0.2
0.3
0.4
0.5
Wavelength (nm)
EQE
(%) o
r Abs
orpt
ion
(arb
. uni
ts) P3HT:PI-BT EQEP3HT AbsorptionPI-BT Absorption
GIXS - Acceptor Only XRD"
HPI-BT spun from chlorobenzene NI-BT spun from chloroform
HPI-BT NI-BT
2.06
2.06 27.3°
NS
N
N
O
O
N
O
O
GIXS – Acceptor Crystallization"
• HPI-BT appears to be much more crystalline than NI-BT!
P3HT:HPI-BT (CB) P3HT:NI-BT (CF)
P3HT Only - CB P3HT Only - CF
Why are fullerene based OPVs better than HPI-BT?"
• Mixing between fullerenes and polymers is significant!
Miller et al., Adv. Mat. 2012 DOI: 10.1002/adma.201202293
Bartelt et al., Adv. Ener. Mat. 2012 DOI: 10.1002/aenm.201200637
Three-phase vs. two-phase morphology"
39
Two-Phase System Three-Phase System
Donor Acceptor
• How can mixing between donor and acceptor increase quantum efficiency?!
Three-phase morphology and charge separation"
• Disorder in mixed phase increases band gap!• Energetic driving force to transfer charge from mixed
phase to more ordered donor and acceptor phases!
40
Mixed HPI-BT
Mixed P3HT
HPI-BT
P3HT
Poor mixing of HPI-BT in P3HT?"
• Miscibility limit of HPI-BT in P3HT is less than 5 wt%!
15% HPI-BT 5% HPI-BT
0% HPI-BT 100% HPI-BT
Poor mixing of HPI-BT in PDHTT?"
• Miscibility limit of HPI-BT in PDHTT is less than 5 wt%!
10% HPI-BT 5% HPI-BT
0% HPI-BT 100% HPI-BT
Poor mixing of HPI-BT in RRa-P3HT?"
• Low mixing even in amorphous polymers!
15% HPI-BT 10% HPI-BT
0% HPI-BT 5% HPI-BT
Computational Modeling to Help with Synthesis"
Computational modeling courtesy of Drs. Ross Larsen and Travis Kemper, NREL!
NS
N
S SNC
O
O
CN
O
O
Gap (eV)! B3LYP/6-31g*! 2.374!
HOMO (eV)! B3LYP/6-31g*! -5.882!
LUMO (eV)!B3LYP/6-31g*! -3.508!
cyanoester
Gap (eV)! B3LYP/6-31g*! 2.212!
HOMO (eV)! B3LYP/6-31g*! -5.640!
LUMO (eV)! B3LYP/6-31g*! -3.428!
NS
N
S SS
N NS
O
S
O
S
Computational Modeling to Help with Synthesis"
Computational modeling courtesy of Drs. Ross Larsen and Travis Kemper, NREL!
rhodanine
Non-fullerene acceptors"
• Lower efficiencies than fullerenes due to lower JSC and lower FF!
4.0% PCE
Zhang et al., Adv. Mater. 2013, ASAP DOI: 10.1002/adma.201300897
4.1% PCE
Mori et al., Adv. Energy Mater. 2013, ASAP DOI: 10.1002/aenm.201301006
Earmme, et al. J. Am. Chem. Soc. 2013 ASAP, dx.doi.org/10.1021/ja4085429
with P3HT 2.9% PCE
Zhou et al. Chem. Commun., 2013, 49, 5802.
all polymer PSEHTT: PNDIS 3.3% PCE
Ternary BHJ Cells"
Can we Improve Light Absorption in BHJ OPV?"• What happens if we add a very high extinction
coefficient dye to P3HT/PCBM solar cell?!
Honda, S. et al, ACS App. Mater. & Inter. 2009, 1(4), 804–810. Honda et al, Adv. Energy Mater. 2011, 1, 588–598.
Thin line-Before
annealing
Dashed line - No dye
Nature Photonics Paper (2013) "
49
Extra photocurrent
squaraine dye
Naphthalocyanines better than Phthalocyanines"
NNN
NN N NNSi
O
O
Si
Si
• Red shifted absorption • 2X higher extinction coefficient
Naphthalocyanines Syntheses"
NC CN
NH3, NaOCH3, dry MeOH
N
N NN N
N N
N
Si OHHOSiCl4, dry quinoline
NH
NHHN
NH4OH, pyridine
Br BrNBSAIBN
CCl4
NaI
DMF
Fumaronitrile91% 55%
N
N NN N
N N
N
Si OHHO
ClSi(hex)3, pyridine
NNN
NN N NNSi
O
O
Si
Si
70%
75%
40%
Prepared by Dr. Bogyu Lim
Absorption spectra – thin film"
200 400 600 8000
0.2
0.4
0.6
0.8
1
Wavelength (nm)
Nor
mal
ized
Abs
orba
nce
(a.u
.)
P3HT PC61BM SiNcb)
Increased Current in P3HT:PCBM"
• Increase in JSC with addition of SiNc!– Stable VOC but decrease in FF, especially higher than 8 wt%!
• BASF P3HT:Nano-C PC60BM!– Devices with Rieke P3HT have the same trend with slightly lower
efficiencies!
-1 -0.5 0 0.5 1-20
-10
0
10
20
Voltage (V)
Cur
rent
Den
sity
(mA
cm
-2)
0 wt%4 wt%8 wt%12 wt%20 wt%
Table&1.&P3HT:PC60BM&device&performance&with&increasing&tAbutyl&SiNc&dye&concentration.&
Dye$Conc.$(wt%)$
JSC$(mA$cm32)$ VOC$(V)$ FF$(%)$ PCE$(%)$
0$ 9.4$(10.1)$ 0.60$(0.62)$ 67$(71)$ 3.80$(4.12)$
2$ 10.1$(10.5)$ 0.62$(0.63)$ 65$(68)$ 4.11$(4.43)$
4$ 10.1$(10.7)$ 0.63$(0.64)$ 65$(68)$ 4.18$(4.42)$
6$ 10.7$(11.1)$ 0.62$(0.64)$ 64$(69)$ 4.27$(4.56)$
8$ 11.4$(12.1)$ 0.62$(0.64)$ 63$(68)$ 4.46$(4.92)$
10$ 11.6$(12.5)$ 0.61$(0.63)$ 62$(68)$ 4.46$(4.80)$
12$ 12.4$(13.7)$ 0.62$(0.62)$ 57$(61)$ 4.36$(4.91)$
15$ 11.2$(14.0)$ 0.61$(0.62)$ 59$(64)$ 3.97$(4.69)$
20$ 11.1$(14.2)$ 0.60$(0.62)$ 58$(64)$ 3.92$(4.93)$
aPerformance$values$are$averages$with$champion$cell$values$in$parentheses.$
t-butyl-SiNc unannealed t-butyl-SiNc annealed
400 600 8000
0.1
0.2
0.3
0.4
0.5
0.6
0.7
Wavelength (nm)
Exte
rnal
Qua
ntum
Effi
cien
cy (E
QE)
0%2%4%6%8%10%12%15%20%
a)
300 400 500 600 700 800 9000
0.1
0.2
0.3
0.4
0.5
0.6
0.7
Wavelength (nm)
Exte
rnal
Qua
ntum
Effi
cien
cy (E
QE)
0%2%4%6%8%10%12%15%20%
b)
300 400 500 600 700 800 9000
0.2
0.4
0.6
0.8
Wavelength (nm)
Exte
rnal
Qua
ntum
Effi
cien
cy
0 wt%3 wt%6 wt%9 wt%12 wt%15 wt%20 wt%
b)
Energy Level Comparison (Schematic)"
• SiNc energy levels must be just in the sweet spot!• P3HT & PCBM allows for charge transport to proceed normally!• Extra 830nm peak possibilities!
– Coupling to PCBM!– Dimer/aggregate formation!
P3H
T
SiN
c
PC
60B
M
No dye
20% dye with peripheral t-butyl groups
20% dye without peripheral t-butyl groups
unannealed annealed
Conclusions"
• Very interdisciplinary research projects!!– Chemistry, device physics, computation, surfaces, etc!
• Working together with CSM (physics, materials, Chem Eng), NREL, CU Boulder. UCSB!
• Using relatively simple chemistry to attack technology bottlenecks!
Acknowledgements
• Co-PIs – Michael McGehee, Mark Lusk, Sean Shaheen, Michael Chabinyc, Dana Olson, Ross Larsen
• Synthesis – Dr. Xu Han (now at DuPont R&D Shanghai), Dr. Andrew Higgs (now at Washington & Lee University), Dr. Bogyu Lim (now at LG Korea), Dr. Unsal Koldemir, Dr. Tianlei Zhou, Ms. Yuting Shi
• Device Fabrication/Characterization/Computation – Jason Bloking, Jack Kastrop, Andrew Pontec, Travis Kemper, Dave Ostrowski, Huashan Li
• Funding Sources:
Acknowledgements"
Colorado School of Mines Stanford
Si147H96(Z2OCH3)4 Si147H96(Z2H2OCH3)4
1.7 nm
Si147H96(Z2OCH3)4 Si147H96(Z2H2OCH3)4
Si147H96(C4H7)4
1.7 nm
N
H3CO
H3CO
N
H3CO
H3CO
Other Projects in the Sellinger lab:
Silicon Quantum Dots with Prof. Mark Lusk at CSM
• Hole Transport Materials and Organic/Energy Relay Dyes for Dye Sensitized Solar Cells (DSSC)!
S
N
H3CO
H3CO
S CN
O
OH
NN N
H3CO
H3CO OCH3
OCH3
Other activities in the Sellinger group (http://chemistry.mines.edu/faculty/asellinger/asellinger.html)
• Scintillating Materials for Application in the Detection of Alpha/Neutron Particles and Gamma Radiation!
• Tailored Silanes, Phosphonic and Carboxylic Acids for Tuning the Workfunction of Transparent Electrodes and Buffer Layers!
Thank you!!