opv stability – from materials to modules -...
TRANSCRIPT
OPV Stability –From Materials to Modules
H.-J. Egelhaaf
OPV: AdvantagesOPV: Advantages
Design features:• Flexible, thin, light-weight• Printable in various widths
• Low light sensitivity (indoor/outdoor)
• Off- angle performance
• Multiple colors: red, green blue
• Roll-to-roll printed
• Transparent version• Customized voltage
Arch Aluminum & Glass Curtain WallTamarac, Florida
Target: Building Integrated Applications
KonarkaNew Bedford, MA
Green HousePlants’ View
Bus ShelterSan Francisco, CA
Lifetime(3 - 5 years)
Efficiency(>3%)
Costs(<1 €/Wp)
Requirements for any PV technology
A successful product must fulfil all 3 requirements Efficiency, Lifetime and Cost
Required for Building Integrated Applications: > 6% (module!)
Effi
cien
cy (
%)
20001995
NREL
NREL
NREL
NREL
United Solar
United Solar12
8
4
0
16
20
University ofLausanne
2005
UCSBCambridge
NREL
U. Linz SiemensKonarka
Konarka
Sharp
Siemens
Konarka
Thin Film Technologies
Cu(In,Ga)Se2
CdS/CdTe
a- Si/a-SiGe
Emerging PV
Dye cells
OPV (polymer)
2010
1
28
4
0
16
20
OPV single junctionOPV single junction
Year
Konarka
PlextronicsUCSB
EPFL(SSDSSC)
SolarmerSolarmer
Heliatek
0
200
400
600
800
1,000
1,200
1,400
0
10
20
30
40
50
60
5 AM 6 AM 7 AM 8 AM 9 AM 10 AM 11 AM 12 PM 1 PM 2 PM 3 PM 4 PM 5 PM 6 PM 7 PM 8 PM 9 PM
Sol
ar I
rra
dian
ce (W
/m2 )
No
rma
lized
Ene
rgy
(wat
t hou
rs)
Konarka OPV
a-Si
c-Si
CIGS
Solar Irradiance
Competitive Testing - Energy Collection on 08/01/10
Panels are Normalized to 5 Wattsmeasured in standard lab conditions
Higher Efficiency at Low Light
Higher efficiency at
higher temperatures
20-35% more
energy collected
in one day (with
respect to std lab
conditions) than
competitive PV
technologies.
Higher Measured Efficiency in Usage Conditions
Requirements for any PV technology
A successful product must fulfil all 3 requirements Efficiency, Lifetime and Cost
Lifetime(3 - 5 years)
Efficiency(>3%)
Costs(<1 €/Wp)
Building Integrated Applications: < 1 €/Wp (module)
Requirements for any PV technology
A successful product must fulfil all 3 requirements Efficiency, Cost and Lifetime
Lifetime(3 - 5 years)
Efficiency(>3%)
Costs(<1 €/Wp)
Flex Applications (niche markets?): > 5 yearsBuilding Integrated Applications: > 15 years in 2011
> 20 years in 2012
OverviewOverview of Degradation of Degradation MechanismsMechanisms
Towards 20 Years Lifetime
The complexity of the problem requiresbreaking down the task into three levels:
- Materials (Degradation of Organic and Inorganic Components)
- Solar Cells(Decay of Performance)
- Solar Modules(Cells + Buss Bars + Packaging + ElectricalConnections)
MaterialsMaterials
Understanding the degradation mechanismswill help make OPV intrinsically more stable• Longer life times
• Save on costs for packaging
Degradation of the polymer depends on:- the chemical structure of the polymer- the environmental conditions- the composition of the photoactive blend
PhotoPhoto --oxidation of P3HT: wavelengthoxidation of P3HT: wavelength
300 400 500 600 700 800
1E-7
1E-6
0.0
0.2
0.4
0.6
0.8
1.0
Effe
ctiv
enes
sIrradiation wavelength / nm
1-10-E
400 500 600 7000.0
0.2
0.4
0.6
0.8
1.0
Abs
orpt
ion
Wavelength λ[nm]
300 400 500 600 700 800
1E-7
1E-6
1E-5
0.0
0.2
0.4
0.6
0.8
1.0
1.2
Effe
ctiv
enes
s
Irradiation Wavelength [nm]
1-10-E
400 500 600 7000,0
0,5
1,0
1,5b
Abs
orba
nce
Wavelength λ [nm]
The PCQY does not follow the absorption spectrumradical mechanism very probable
Regio-random P3HT Regio-regular P3HT
ReactionSpectra
ActionSpectra
H. Hintz, H.-J. Egelhaaf, L. Lüer, J. Hauch, H. Peisert, Th. Chassé, Chem. Mater. 23 (2011) 145
PhotoPhoto --oxidation of P3HT: wavelengthoxidation of P3HT: wavelength
0 5 10 150.0
0.2
0.4
0.6
0.8
1.0 UV 365
Abs
nor
mal
ized
Time*103 [min]
a
0 20 40 60 800.0
0.2
0.4
0.6
0.8
1.0
VIS 525
Abs
nor
mal
ized
Time*103 [min]
b
0.0 0.2 0.4 0.6 0.8 1.00.0
0.2
0.4
0.6
0.8
1.0
1.2
UV/VIS loss at 520nm [norm]
Abs
orba
nce
[nor
m]
VIS 525 b 0.0 0.2 0.4 0.6 0.8 1.0
0.0
0.2
0.4
0.6
0.8
1.0
1.2
Abs
orba
nce
[nor
m]
UV/VIS loss at 520 nm [norm]
UV 365 a
S
n
Different reaction pathways for different wavelengths
S
n
λirr = 365 nm λirr = 525 nm
H. Hintz, C. Sessler, H. Peisert, T. Chassé, H.-J. Egelhaaf, in preparation
FTIR signals
PhotoPhoto --oxidation of P3HT: Humidityoxidation of P3HT: Humidity
0 100 2000,0
0,2
0,4
0,6
a
Abs
orba
nce
time / min
1
2
3
Time trace of absorption maximum during degradation under1: oxygen2: humidified oxygen (100% rel. Humidity)3: humidified nitrogen (100% rel. Humidity)
0 20 40 60 80 1002
3
4
5
6
100
150
200
reac
tion
rate
/ 10
-3m
in-1 b
Relative humidity % at 22°C
reaction rate %
H. Hintz, H.-J. Egelhaaf, L. Lüer, J. Hauch, H. Peisert, Th. Chassé, Chem. Mater. 23 (2011) 145
Effect of Fullerene Structure
EF1 (-3.53 eV)
F2 (-3.60 eV)
F3 (-3.66 eV)
F4 (-3.70 eV)
F5 (-3.75 eV)
F6 (-3.80 eV)F7 (-3.81 eV)
F8 (-3.83 eV)
� PCBM
P3HT Fullerene
HOMO
LUMO
LUMO
e-
e-
hν
Fullerene LUMO energy
Effect of Fullerene on P3HT Photobleaching
�All fullerenes stabilize P3HT
�Stabilizing factor: 2-7 (5 for PCBM)
0 5 10 15 20 25 30 35 40 45 500
11
22
33
44
55
66
77
88
99 Fullerene (LUMO):
F1 (-3.53 eV)
F2 (-3.60 eV)
F3 (-3.66 eV)
F4 (-3.70 eV)
F5 (-3.75 eV)
F6 (-3.80 eV)
F7 (-3.81 eV)
F8 (-3.83 eV)
pristine P3HT
no
rmal
ize
d O
D a
t P
3H
T m
axi
mu
m [
%]
time of degradation [h]
A. Distler, H.-J. Egelhaaf, D. Waller, K.-S. Cheon, S. Rodman, D. Guldi, in preparation
Photobleaching vs. Fullerene LUMO
-3.50 -3.55 -3.60 -3.65 -3.70 -3.75 -3.80 -3.85
40
45
50
55
60
65
70
75
80
85
90
95
100
time of degradation:
0 h
0.5 h
1 h
2 h
3 h
5 h
10 h
30 h
50 h
no
rma
lize
d O
D a
t P
3H
T m
axi
mu
m [
%]
LUMO [eV]
maximum stabilization effect (F5)
Effect of Polymer Structure / Fullerene
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.70.00
0.25
0.50
0.75
1.000.00
0.25
0.50
0.75
1.000.0
0.5
1.0
1.5
2.0
D/D0 D/D0 + DIO F/F0 F/F0 + DIO
c) Si-PCPDTBT
00
xPCBM
(w/w)
D/D0 F/F0
b) P3HT
a) C-PCPDTBT
D/D0 D/D0 + DIO F/F0 F/F0 + DIO
P. Kutka, A. Distler, T. Sauermann, H.-J. Egelhaaf, D. Di Nuzzo, S.C.J. Meskers, R.A.J. Janssen, in preparation
Fluorescence Intensity and Degradation Rateas a Function of PCBM content
S
n
PCBM enhances degradation
PCBM reduces degradation
PCBM slightlyreduces degradation
Degradation rate
Fluorescence intensity
Fluorescence intensity
Degradation rate
Solar Cells Solar Cells
Overall Loss of Efficiency consists of reversible and irreversible component
Degradation by Light and OxygenDegradation by Light and Oxygenair
N2
Irreversible Component
-0.50 -0.25 0.00 0.25 0.50 0.75 1.00
-5.0
0.0
5.0
10.0
15.0
20.0
undegraded 2% degraded 5% degraded
Cur
rent
den
sity /
mA*c
m-2
Voltage / V
b
Absorption and Jsc Loss after Illumination in Synthetic Air and Annealing in Nitrogen
Minor Changes in Absorption lead to 50% Jsc Loss
300 400 500 600 700 8000.0
0.5
1.0
1.5
O.D
.
Wavelength (nm)
0% 2% 5% 10% 20%
Irreversible Degradation Leads to StrongPhotoluminescence Quenching
600 700 800 9000.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
Pho
tolu
min
esce
nce
(106 c
ount
s)
Wavelength (nm)
0% 2% 5% 10% 20%
Absorption loss [%] 2 5 10 20
PL loss [%] 23 54 57 76
Loss in excitons which recombine in the P3HT domains!What about all the other excitons?
PCBM
P3HT
-
+
-0.2
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
(d)(b)
−∆T
/T (
10-2)
0% 10% 20%
(a) (c)
0% 10% 20%
0 150 300 450 600 750 900
Time Delay (ps)0 2 4 6 8 10 12 14
-0.2-0.10.00.10.20.30.40.50.60.7
DP
ExA
−∆T
/T (
10-2)
Time Delay (ps)
Effect of Degradation on Excited States
- Strong effect of degradationproducts on excitons (ExA) on a very short timescale
- Polaron (DP) lifetime slightlydecreases with degradation dueto recombination via degradationproducts
Transients at Different Degrees of Bleaching
F. Deschler, A. De Sio, E. von Hauff, P. Kutka, T. Sauermann, H.-J. Egelhaaf, J. Hauch, E. Da Como, Adv. Funct. Mater., accepted
HOMO
LUMO
P3HT
En
erg
y
PCBM
(a) (b) (d)(c)
τHEx-Ext τExd-Polt τHEx-Polf τPolf-r
Reversible Oxygen Effect on jV-curves
Solar Cell with inverted structure and Ag grid electrode
Reversible oxygen doping leads to reduction of jscA. Seemann, T. Sauermann, C. Lungenschmied, O. Armbruster, S. Bauer, H.-J. Egelhaaf, J. Hauch, Solar Energy 85 (2011) 1238
Temporal behaviour of cell performance
Performance loss is mainly due to loss in jsc (partly reversible) and to loss in FF (irreversible)
Cell parameters: efficiency, jsc, Voc, FF
A. Seemann, T. Sauermann, C. Lungenschmied, O. Armbruster, S. Bauer, H.-J. Egelhaaf, J. Hauch, Solar Energy 85 (2011) 1238
Oxygen Effect on CELIV measurements
CELIV traces Charge carrier concentration
Oxygen doping leads to increase in charge carrier concentration- Slow in the dark- accelerated under illumination
A. Seemann, T. Sauermann, C. Lungenschmied, O. Armbruster, S. Bauer, H.-J. Egelhaaf, J. Hauch, Solar Energy 85 (2011) 1238
Charge Carrier Formation Monitored by ESR
Light + Oxygen Formation of Metastable Charge Carriers
ESR signal in the darkand under illumination
Time trace of ESR signal upon light ‚on under air and light off under vacum
A. Aguirre, S.C.J. Meskers, R.A.J. Janssen, H.-J. Egelhaaf, Org. Electronics (2011)
Mechanism of Oxygen Doping
-5.1
-3.7
-2.9
-6.1
E / eV
P3HT O2 PCBM
hν
1
2
4
3
Effect on Device: Simulation with PC1D
Doping leads to the formation of a space charge region in front of the anodeShielding of the electric field in the bulkReduced charge carrier extraction
Solving the fully coupled set of Differential Equationsfor an Effective Medium Bulk Semiconductor
Intrinsic Degradation
• Active layers
• Interfaces
• Electrodes
Extrinsic Degradation
• Buss Bars, Leads
• Packaging films
• Adhesives
Lifetime is a
System
Property
Modules
Lowell, MA
Southern Florida Southern Arizona
Location Lowell, MA.
facing solar south at 42° ≈1600 kWh / m2
2 measurement modes:
a) Outdoor JV in 4th quadrant with
modulated load and wireless data
read out
b) Periodic characterization under
standard solar simulator
Outdoor Testing - Konarka
Encapsulation of the ModuleEncapsulation of the Module……
Substrate
Encapsulation
Electrode
Buss Bar
Active Layers
0%
20%
40%
60%
80%
100%
120%
140%
No
rma
lize
d E
ffic
ien
cy
Gen1, Lowell Rooftop
Gen 2, Lowell rooftop
Gen2, South Florida
Two years outdoor without drop in performance.
……affordsaffords OutdoorOutdoor LT > 2yrsLT > 2yrs
Stress Factors
• Light
• Humidity
• Temperature
• Oxygen
• Hot/Cold cycles
• Wet/Dry cycles
• Wind
• Rain
• Hail
• Pollutants
Intrinsic Degradation
• Active layers
• Interfaces
• Electrodes
Extrinsic Degradation
• Buss Bars, Leads
• Packaging films
• Adhesives
Lifetime is a
System
Property
Accelerated Lifetime Testing
Equipment Test EquipmentSolar Simulator AM1.5G, 100 mW/cm2
Dry Ovens Pass 1000 hrs at 65°C
Steady –State OvenTemperature / Humidity
Pass 1000 hrs @ 65°C / 85 % r.h.(extended 85°C/85 % r.h.)Thermal Cycling
ChamberTemperature / Humidity
3 hrs cycle, -40°C to + 80°C
Light Soaking ChambersTemperature / Humidity / RainUltraviolet Light Chamber
Pass 1000 hrs 65°C/1sun According to IEC + IEEE + ASTM standards
Flex bending > 1000 bends over 50 mm roll
Standard ALT Testing
Building a correlation with outdoor lifetime data.
0.0
0.2
0.4
0.6
0.8
1.0
1.2
0 500 1000 1500 2000 2500
Time [hours]
Nor
m. E
ff. [a
.u.]
65°C/1sun
Lifetime of Production Modules
0.0
0.2
0.4
0.6
0.8
1.0
1.2
0 500 1000 1500 2000 2500 3000 3500 4000 4500Time Hours
No
rm.
Eff
. [a
.u.]
Barrier 3
Barrier 1
Barrier 2
WVTR Barrier 1 >> WVTR Barrier 2 >> WVTR Barrier 3
Lifetime of the modules depends on the adhesive/barrier quality.
65°C/85%rh
Lifetime of Production Modules
Flex Product pre-qualification for letter of compliance
IEC 61646 10.13 damp heat 85°C/85%RH 1000hours “PAS SED”
Flex Productpre-qualification for letter of compliance
IEC 61646 10.11 thermal cycling (50 cycles) + IEC 61646 10.12 humidity freeze (10 cycles) “PASSED”
Acknowledgments
The German Ministry for Education and Research is Acknowledged for Funding
(BMBF project „OPV Stability“)