Study of Carrier Lifetime Measurement
Methods for PID Tested Module
Information Device
Science Laboratory
Kazuki Noguchi1, Mohammad Aminul Islam1, Takuya Oshima1, Yasuaki Ishikawa1,
Hidenari Nakahama2, Yukiharu Uraoka1
1Nara Institute of Science and Technology, 2Nisshinbo Mechatronics Inc., Japan
Potential Induced Degradation (PID)
The phenomenon occurs often in the large-scale
solar power generation system.
PID mechanism of the p-type crystalline Si solar cell
600-1,000V
・Disappearance of depletion layer by band bending
effect caused by diffusion of alkaline ions to Si surface.
・Leak path formed at the defect intrusion of alkaline ions.
Glass
EVA
EVA
Back sheet
p-type crystalline
Si solar cell
TAS
Comparison of TAS and m-PCD Summary
Temperature: 85ºC
Humidity: 85%
Carrier lifetime measurementSample and accelerated (PID) test
Acknowledgement
E-mail: [email protected]
This work is partially supported by NEDO, Japan.
The measurement of TAS was conducted at the Nano-Processing
Facility, supported by IBEC Innovation Platform, AIST.
Ad1 /10-4td1 /10-6 Ad2 /10-4
td2 /10-6 Ad3 /10-4td3 /10-6
43.90 0.24 26.50 10.65 7.31 44.59
Fitting equation:
△A = Ad1exp(-t/t1)+Ad2exp(-t/t2) )+Ad3exp(-t/t3)
Microwave PhotoConductivity Decay (m-PCD)
Transient Absorption Spectrometry (TAS)
Deterioration factor
Emission point Dark point
tm-PCD
0 100 200 3000
2
4
6
8
Decay t
ime [m
s]
PID tested time [hour]
Emission point
Dark point
0 100 200 3000
5
10
15
Decay t
ime [m
s]
PID tested time [hour]
t2
Emission point
Dark point
0 100 200 3000
10
20
30
40
50
Decay t
ime [m
s]
PID tested time [hour]
t3
Emission point
Dark point
0 100 200 3000
0.1
0.2
0.3
Decay t
ime [m
s]
PID tested time [hour]
Emission point
Dark point
t1
Measurement points
-1000VSample PID test
EL images0h 100h 200h 300h
Measurement point
Nondestructive inspection.
Able to observe the degradation of the cell.
Able to meas. at arbitrary point in the cell.
Purpose・ Alkaline ions (Na, K) move
to the cell surface from glass.
Effect of alkaline ions
V. Naumann, et al., Sol. Energy Mater. Sol. Cell 120, 383 (2014)
Fresh p-type single Si solar cell
Lifetime measurement method used for Si wafer and solar cells.
Simple measurement system using an optical fiber.
m-PCDTAS
Complicated optical system Simple optical system
m-PCD can also analyze the carrier lifetime of PID modules like TAS.
Evaluation methods
No quantitative evaluation
PID modules show a short effective-carrier-lifetime
since a band-bending effect happens at the Si surface.
EL and thermography imaging techniques employed for practical use as evaluation methods for PID modules.
Evaluate the carrier lifetime of the PID tested
module to clarify the mechanism of PID.
Carrier transition mechanism
practical use as evaluation
methods for PID modules.
Carrier lifetime was reduced at all points by PID test.
Residential Mega solar
t1 is fast decay directly associated with carrier trapping to the mid gap defect
state in the vicinity of the conduction band,
t2 is slow decay that is attributed to carrier trapping to the deep-level state from
the conduction band and
t3 is slowest decay attributed to carrier relaxation in the valence band edge.
Emission point t1 /ms t2 /ms t3 /ms tm-PCD /ms
0 h 0.24 12.10 49.0 7.92
100 h 0.13 1.37 17.0 2.94
200 h 0.20 7.49 24.5 3.27
300 h 0.21 4.34 20.5 3.10
t1 didn’t change at any points and t1was about 0.2 ms.
At the emission points, t2 and t3were large, and at the dark points, they decreased remarkably.
Lifetimes from m-PCD were also changed by PID tested time as that from TAS(~10 ms:similar range of t2).
Lifetime from m-PCD changed in the same way as t2 and t3.
Carrier lifetime for PID tested module were measured using TAS
and m-PCD.
For TAS measurement, t2 and t3 were significantly reduced by PID.
Lifetime from m-PCD changed in the same way as t2 and t3.
Four different samples:
0h, 100h, 200h, 300h
Localization
Relaxation
E
k
t1
t2
t3
Carrier-phonon
interaction
Shallow trap
Mid-gap trap
Deep acceptor trap
Valance band edge
Pu
mp
en
erg
y (
eV
)
EF
P-03
SAYURI-PV 2016
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