Upload
others
View
2
Download
0
Embed Size (px)
Citation preview
Director: Mike McGeheeExecutive Director: Alan SellingerDeputy Director: Peter Peumans
$5 million/year for five years from Saudi Arabia (KAUST)
Center for Advanced Molecular Photovoltaics
CA M
P
Center for Advanced Molecular Photovoltaics
Background on KAUST
• King Abdullah University of Science & Technology (KAUST) http://www.kaust.edu.sa/
– Endowment of $20 B
– Women and men educated together.
– Research thrusts in:
• Resources, Energy and Environment• Biosciences and Bioengineering• Materials Science and Engineering• Applied Mathematics and Computational Science
KAUST in May 2008
KAUST one month later
KAUST future (opening Sep. 2009)
Covering less than 1 % of the land with solar cells could meet our electricity needs
6 Boxes at 3.3 TW Each
Large Scale Printing of Semiconductors!
Attractive properties:
•Abundant: ~100,000 tons/year
•Mature industry/markets
•Low materials cost: ~1$/g 17¢/m2
•Low‐cost manufacturing
•Non‐toxic
CuPcCopper Phthalocyanine
Molecular Semiconductors
8
N
N
N
N
Cu
CAMP Goals
• 15 % Efficiency
• 10-20 year lifetime
• $30/ m2
Molecular PV Silicon PV
Training of top quality students for solar industry!
• 12 % Efficiency
• >20 year lifetime
• $350/ m2
Power Conversion Efficiency (PCE)
FF*Isc*
Incident Power
VOCη =
Isc
Voc
FF
Mutolo, K., et al JACS (2007)
Forrest, MRS Bulletin 2005
Physics of Organic Solar Cells
Device Fabrication and Characterization
Mike McGehee
Peter Peumans
Michael Graetzel (EPFL)
13
Polymer-fullerene bulk heterojunction cells
PEDOT
Ca/Al~2
00 n
m th
ick
X-ray Diffraction pBTTT:PC[71]BM Blends
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
SS
~21.
5Å
+
1:41:11:0
(100)p
(200)p
(300)p
(400)p
(003)p
(010)p
(100)i
(200)i
(300)i
(400)i
(500)i (402)i
SS
SS
SS
SS
Consequences of Intercalation
Dense Side-Chains Less Dense Side-Chains
Optimal blend ratio ~ 1:3Optimal blend ratio ~ 1:1
e.g. P3HT e.g. pBTTT
Better for avoiding back electron transfer
Better for splitting excitons
acceptordonor
EF
3
4 521
anode cathode
21
3
cathodeanodeEF
acceptordonor
Calculated Band Diagrams
donor and acceptorare highly doped
donor is highly doped,acceptor ~ intrinsic
p doped n doped
Effect of Electrical Doping
Liu, Zhao, Rim and Peumans, Adv. Mater., 1065-1070 (2008).
Dye sensitized solar cells
Dye: Z907 HTM: Spiro-OMeTAD(Spiro)
H.J. Snaith, Adv. Mater. 19, 3187 (2007)
World Record: ~5% Efficiency
Increasing absorption in dye sensitized cells with energy relay dyes
TiO2
Sensitizer Dye
CathodeSpiro-OMeTAD
Fluorescing Dye
FRET
Brian Hardin, Eric Hoke, McGehee, Gratzel
Interface characterization and modification: Stacey Bent
Advanced Optics
Peter Peumans, Mark Brongersma and Shanhui Fan
20
Transparent Electrodes
ITO
glass•Performance•Cost (~$10/m2)•Brittle•Compatibility with plastic substrates
What’s wrong with ITO?
Carbon Nanotube Electrodes
Cur
rent
(mA
/cm
2 ) 0
2
-2
-4
-6
-80 0.2 0.4 0.6-0.2
CNT
ITO
Vout
Nanotube Film PEDOT:PSS Transparent Electrode
Back Electrode
P3HT:PCBMLight Absorber
SunlightSunlight
Solar cell I-V
Efficiency jsc Voc Fill Factor CNT cell 2.5% 7.8 mA/cm2 605 mV 0.52 ITO cell 3.0% 8.0 mA/cm2 610 mV 0.61
Voltage (V)
DARK
M.W.Rowell, et al, APL 2006
plastic (PET) superstrate
Ag Nanowires
Yi Cui, Peter Peumans, Nanoletters, 8, 2008, p. 689. 23
10μm
Radius= 8.36 mm12.5 ohm/sq
Radius= 13.74 mm12.5 ohm/sq
Radius= 4 mm12.6 ohm/sq
Flat12.7 ohm/sq
~20% of transmitted light is scattered
Ag Nanowires
ZnO Nanowires
milky diffusing films
Film cast from nw solution
Alberto Salleo
Molecular Design and Synthesis
27
Quantum-Chemical Calculations
Donor-Acceptor Copolymers
Vertical Transition Energies
Jean-Luc Bredas (Georgia Tech)
Quantum-Chemical Calculations
28
Jean-Luc Bredas (Georgia Tech)
Synthesis
Zhenan Bao
Mark Thompson (USC)
Jean Fréchet (UC Berkeley)
Alan Sellinger
29N
NN
NNNB Cl
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
Sellinger Group
N
N
CN
CN
N
N
NC
NC
NS
N
N
N
CN
CN
N
N
NC
NC
NS
N
V-BT H
V-BT EH
Better solubility•Can be thermally sublimed as well
PQT:VBT EH
80ºC device: Voc = 0.97 V, FF = 0.41, PCE = 1.09%
VBT EH
80 ºC device: Voc = 1.36 V, FF = 0.49, PCE = 0.75%Ooi, Z; Tam, TL; Shin, RYC; Chen ZK; Kietzke, T; Baumgarten, M; Mullen, K; deMello, JC; Sellinger, A, Journal of Materials Chemistry, 2008, 18, 4619–4622.
Work from Mark Thompson’s group at USC
Work from Mark Thompson’s group at USC
N
N
N
N
Cu
CuPc
C60
Work from Mark Thompson’s group at USC
Work from Zhenan Bao’s group at Stanford
Bao, Z et al, manuscript in preparation
Work from Zhenan Bao’s group at Stanford
Okamoto, T.; Jiang, Y.; Qu, F.; Mayer, A. C.; Parmer, J. E.; McGehee, M. D.; Bao, Z. Macromolecules, 2008; 41(19); 6977-6980.
Work from Jean Fréchet’s group at UC Berkeley
Thompson, BC et al, Macromolecules 2007, 40, 7425-7428
Reliability
Reiner Dauskardt
39
Degradation and Reliability of Photovoltaic Devices
Severe operating environments.Exposure to moisture, chemically active environmental species, thermal cycling and UV radiation. Lifetimes are dictated by the loss of adhesion and defect evolution.
Characterize and model mechanisms of defect initiation and evolution accelerated by environment, thermo-mechanical cycling and UV exposure.
Adhesion/Cohesion Sample Preparation
Fabricated 4-point bend adhesion and DCB cohesion test structures using standard epoxy bonding techniques.Similar transparent glass substrates on each side.
Gunes, et. Al. Chem. Rev. 2007.
Glass Substrate
ITO (150 nm )PEDOT:PSS (50-100 nm)
Al (100 nm)Ca (7 nm)
P3HT/PCBM (200 nm)
Epoxy Bond (2 μm)
Glass Substrate
Thin films sandwiched between elastic substrates
FPB adhesion
DCB cohesion
Adhesion/Cohesion Sample Preparation
Gunes, et. Al. Chem. Rev. 2007.
Glass Substrate
ITO (150 nm )PEDOT:PSS (50-100 nm)
Al (100 nm)Ca (7 nm)
P3HT/PCBM (200 nm)
0
2
4
6
8
10
12
Frac
ture
Ene
rgy,
G (J
/m2 )
Solar Cell 1
Solar Cell 2
Solar Cell 3
4-point bend DCB
• XPS reveals similar debond path for DCB and 4-pt bend samples• C ~ 92%, S ~ 6%, O ~ 2%• Suggests cohesive failure in PCBM:P3HT layer and not at the interfaces!
cohesive
failure
• Exciting new research activities in CAMP at Stanford University + partner universities– Very interdisciplinary!
• Working closely with KAUST from Saudi Arabia
• More information: Alan Sellinger ([email protected])
Conclusions