Accelerated Degradation by Light Illumination
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Accelerated Degradation by Light Illumination or Current Injection During Heat Tests on Flexible Thin Film Modules (from the PVQAT TG8 Japan Team's activity) Keiichiro Sakurai 1,2 , Akihiro Takano 2 , Hironori Yanase 2 , Toshiaki Sakai 2 , Hironori Nishihara 2 , Tetsuro Nakamura 2 , Shinji Fujikake 2 , Masayoshi Takani 2 a National Institute of Advanced Industrial Science and Technology (AIST), b Photovoltaic Power Generation Technology Research Association (PVTEC)
Transcript of Accelerated Degradation by Light Illumination
Accelerated Degradation by Light Illumination or Current Injection During Heat Tests
on Flexible Thin Film Modules(from the PVQAT TG8 Japan Team's activity)
Keiichiro Sakurai1,2, Akihiro Takano2, Hironori Yanase2, Toshiaki Sakai2, Hironori Nishihara2,Tetsuro Nakamura2, Shinji Fujikake2, Masayoshi Takani2
a National Institute of Advanced Industrial Science and Technology (AIST),b Photovoltaic Power Generation Technology Research Association (PVTEC)
http://www.nrel.gov/ce/ipvmqa_task_force/
PVQAT TG8 – working on thin film modules
Unique degradation mode observed in a prototypeThin film Silicon flexible module(1)
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Year
0.00.10.20.30.40.50.60.70.80.91.01.11.21.3
Effic
ienc
y (a
rb. u
nits
)
Power GenerationRadiationEfficiency
Pow
er G
ener
atio
n (k
Wh/
kWp・
day)
Am
ount
of S
olar
Rad
iatio
n (k
Wh/
day)
Relocation
99 00 01 02 03 04 05 06 07 08 09 10 11 12
(A.Takano et al, EU PVSEC 2013, 3BO.5.4)
Transparent Electrode (+)
Laser-Scribed Linesfor Unit-Cell Separation
Backside Electrode Plastic-Film Subs trate
a-Si Layer
Metal Electrode (-)
Series-Connect ion Holes Current-Collection Holes
Transparent Electrode (+)
Laser-Scribed Linesfor Unit-Cell Separation
Backside Electrode Plastic-Film Subs trate
a-Si Layer
Metal Electrode (-)
Series-Connect ion Holes Current-Collection Holes
Unique degradation mode observed in a prototypeThin film Silicon flexible module(2)
(A.Takano et al, EU PVSEC 2013, 3BO.5.4)
(Leak points)
EL image
0102030405060708090
100
0 1000 2000 3000Test Time (h)
Out
put P
ower
（ arb
. uni
ts） Damp Heat Test
Damp Heat & Current InjectionTest
Degradation reproduced by Injectingcurrent during damp heat testing(CDH test)
→ made it possible to fix the problembefore mass production!
nip
LOAD
Light
nip
0v+Vpm 0v+Vpm
Current Injection Test Photo Irradiation
Current Flow(Ipm)
Current Flow(Ipm)
nip
LOAD
Light
nip
0v+Vpm 0v+Vpm
Current Injection Test Photo Irradiation
Current Flow(Ipm)
Current Flow(Ipm)
Current injection instead of light irradiation?
Large chamber (small number of panels)Normal current flow
Many panels at one timeReversed current flow
…
(A.Takano et al, EU PVSEC 2013, 3BO.5.4)
Current Injection + DH (CDH) Light Irradiation+ DH (LDH)
White LED
s
glass
mod
ules
Cause of degradation?
EVARoof Shingle
Cell
ETFE
Acetic Acid
Acetic Acid
EVARoof Shingle
Cell
ETFE
Acetic Acid
Acetic Acid
(Roof shingle) 0
50
100
150
200
250
0 1000 2000 3000 4000 5000 6000Damp Heat & Current Injection Test Time （h）
Con
cent
ratio
n of
CH3
CO
OH （
μg/g） Rear Electrode Side
Cell Side
0
50
100
150
200
250
0 1000 2000 3000 4000 5000 6000Damp Heat & Current Injection Test Time （h）
Con
cent
ratio
n of
CH3
CO
OH （
μg/g） Rear Electrode Side
Cell Side
Change EVA to acid‐free encapsulant→ longer lifetime
0102030405060708090
100
0 2000 4000 6000 8000 10000 12000
Damp Heat & Current Injection Test Time (h)
Out
put P
ower
（ arb
. uni
ts）
(A.Takano et al, EU PVSEC 2013, 3BO.5.4)
0102030405060708090
100
0 1000 2000 3000Test Time (h)
Out
put P
ower
（ arb
. uni
ts） Damp Heat Test
Damp Heat & Current InjectionTest
Question…
Is there any difference in results between current injection andlight irradiation?
Would this CDH test reproduce degradations betteron other types of modules as well?・other flexible thin film Si products?・flexible CIGS?・rigid thin films?
(A.Takano et al, EU PVSEC 2013, 3BO.5.4)
Experiments
Flexible TF modules・Thin film Si・CIGS purchased in the market(not really designed for long‐term use)
DryHeat (75～85℃ 20%) (module temperature)With visible light irradiation
Damp/DryHeat withCurrent injection
DryHeat (85℃ 20%)or DampHeat(dark)
(75～85℃ 20%r.h.white (=blue+yellow)LED, power close to1kW/m2)
Outdoor
Compare the degradation(I‐V, EL)
light + DryHeat : I‐V: CIGS flexible product 2
• quick initial degradationfollowed by slow (or no) degradation
• decreased Voc & FF• retained Isc
Note: sample number is small,individual difference may bepresent
0.6
0.65
0.7
0.75
0.8
0.85
0.9
0.95
1
1.05
norm
alize
d maxim
um pow
er
Time
CIGS2 DryHeat
with light
dark
1kΩ
open
light+DryHeat : EL: CIGS2
CIGS2Light+Heat(1kΩ)
CIGS2Heat (dark)
initial
CIGS2Light+Heat(open)
1000hrs500hrs
(Data lost)
3000hrs
EL images darkened within first 500hrs of Light+DryHeat
current + DampHeat : I‐V: CIGS flexible product 2
0
0.1
0.2
0.3
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0.5
0.6
0.7
0.8
0.9
1
0 200 400 600 800 1000 1200 1400 1600
CIGS2 small DampHeat Dark/Dark+Current
S4(Current+Damp,128mA) S5(Current+Damp,128mA)
S6(Current+Damp,128mA) S7(Current+Damp,255mA)
S8(Current+Damp,255mA) S9(Current+Damp,255mA)
S10(Current+Damp,383mA) S11(Current+Damp,383mA)
S12(Current+Damp,383mA) S15(DarkDamp)
S16(DarkDamp) S17(DarkDamp)
Degrades too fast underDampHeat conditions‐‐ couldn't observe anydependency with current
S13(Light+DampHeat, open)
S14(Light+DampHeat, shunt)
S16(Dark+DampHeat)
S17(Dark+DampHeat)
Initial 500h 1000h
light+DampHeat : EL: CIGS2
Darker EL with light + DampHeat too ‐‐‐ darker EL seems clear(However, difference in I‐V not distinguishable up to 1000hrs‐‐ further tests underway)
CIGS2: Destructive analysisETFE
Barrier layer
Cells
BacksheetEdge seal EVA
rip off EVA close to the cell• Ion Chromatography• FT‐IR (ATR)
Samples:• Reference (as‐purchased)• Dark+DryHeat 3900hrs• Light+DryHeat 3100hrs
CIGS2: Ion Chromatography(Reference / Dark+DryHeat / Light+DryHeat)
Acetic acid content in EVA（μg/g）
Reference (as‐purchased) 10Dark+DryHeat 140Light+DryHeat 34
Increased acetic acid content by DryHeatLarge difference between Light and Dark samples
CIGS2: FT‐IR comparison(Dark vs Light, both DryHeat)
‐OH
‐COOH
water?
More ‐OH and ‐COOH observed in EVA of Dark+DryHeat sample
SummaryWhat can be said now:Adding current injection (or light illumination) to conventional DH test・was a must for at least one prototype flexible TF‐Siactually did a crucial job to improve a product’s durability
・may work better for at least one flexible CIGS product• darker EL by light illumination during DryHeat/DampHeat tests• degradation in Voc&FF by light illumination (possible)• change in acetic acid content in EVA by light illumination (possible)
If it is proved that the current injection does work better for multiple samples,then it would be worth considering modification of the IEC standard.
More “not‐so‐robust” samples & tests are needed.If you can contribute, join us!
Thank you!
Further experimentsSmall flexible modules
continue to gather more data (add more samples)
・Compare with outdoor results・Add rigid modules as well?
Large flexible modules・Light + Heat:
underway at AIST・Outdoor, Current injection+DH:
To be tested at FSEC
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