Extended Thermal Cycling Lifetime Testing on Crystalline Silicon Solar Modules with Artificially Introduced Defects

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1 Extended Thermal Cycling Lifetime Testing on Crystalline Silicon Solar Modules with Artificially Introduced Defects J. Schmauder, K. Kurz, A. Schneider International Solar Energy Research Center (ISC) Konstanz Rudolf-Diesel-Str. 15, Konstanz

2 Overview Motivation Experimental design Samples Results after > 800 TC cycles Conclusion J. Schmauder, 5CO.13.3, EUPVSEC 2016, Munich, June 22nd,

3 Motivation Accelarated aging tests are used to investigate the durability and safety of PV modules. Thermal cycling (TC) testing is done in PV module certification and defined in IEC (200 cycles, - 40 C.. 85 C) 200 cycles are considered not enough as they correspond to ~10 years of field installation in an average climate In this work we try to investigate the evolution of crack and low shunt defects in crystalline silicon solar modules during extended TC treatment J. Schmauder, 5CO.13.3, EUPVSEC 2016, Munich, June 22nd,

Experimental design TC test oriented at IEC 61215 TC from -40 C to

current flow of 8 A Current flow only on working hours due to safety

= ~ 7 months! (IEC 61215: 200 cycles) Characterization in avg.

4 Experimental design TC test oriented at IEC TC from -40 C to 85 C Cycle period of ~ 6 h For T > 25 C electr. current flow of 8 A Current flow only on working hours due to safety reasons (~ 1/3 of regular test time) Test stoppped after 813 cycles = ~ 7 months! (IEC 61215: 200 cycles) Characterization in avg. every 10 days (21 times): IV EL J. Schmauder, 5CO.13.3, EUPVSEC 2016, Munich, June 22nd,

5 Samples Samples J. Schmauder, 5CO.13.3, EUPVSEC 2016, Munich, June 22nd,

Sample design Typ. industrial module design: 3.

6 Sample design Typ. industrial module design: 3.2 mm textured front glass 450 µm EVA Standard full area aluminium solar cell (Cz and mc) 1.6 mm ribbons, 60/40 Sn/Pb Standard white backsheet Cell efficiencies: Cz: 15.7% % mc: 15.2% % Soldering through semi-automatic stringer Lab-scale laminator J. Schmauder, 5CO.13.3, EUPVSEC 2016, Munich, June 22nd,

7 Sample groups TC no TC (but 8 A current) Cz mc Cz mc Ref Ref Ref Defect1 Defect1 Defect1 Defect1 Defect2 Defect2 Defect2 Defect2 Defect3 Defect3 Defect3 Defect3 Defect4 Defect4 Defect4 Defect4 25 samples in total 1-2 samples for each defect -> no statistics, only examples! J. Schmauder, 5CO.13.3, EUPVSEC 2016, Munich, June 22nd,

8 Sample defects TC Field Simulation Crack Breakdown Ω Laser Bird 3-4 Ω Ω Low shunt defects J. Schmauder, 5CO.13.3, EUPVSEC 2016, Munich, June 22nd,

9 Results Results - Reference samples J. Schmauder, 5CO.13.3, EUPVSEC 2016, Munich, June 22nd,

91 No changes in I SC and V OC R Sh slightly increases FF and P mpp drop with ~ 0.

10 Reference sample - Cz Linear regression Slope (= relative change after 100 cycles) R 2 V OC % 0.09 I SC % 0.40 FF % 0.92 R Sh % 0.50 P mpp % 0.91 No changes in I SC and V OC R Sh slightly increases FF and P mpp drop with ~ 0.5 % / 100 cycles -> Series resistance increase J. Schmauder, 5CO.13.3, EUPVSEC 2016, Munich, June 22nd,

Reference sample - Cz Before testing 331

stays open in short period After testing J.

11 Reference sample - Cz Before testing 331 cycles 385 cycles 405 cycles Only single new finger interruption detectable Finger interruption occurs, closes, opens again and stays open in short period After testing J. Schmauder, 5CO.13.3, EUPVSEC 2016, Munich, June 22nd,

12 Reference samples - mc Linear regression no TC TC Slope R 2 Slope R 2 V OC % % 0.00 I SC % % 0.34 FF % % 0.92 R Sh % % 0.13 P mpp % % 0.82 J. Schmauder, 5CO.13.3, EUPVSEC 2016, Munich, June 22nd,

13 Reference samples - mc no TC Before testing After testing TC J. Schmauder, 5CO.13.3, EUPVSEC 2016, Munich, June 22nd,

14 Results Results - Cracks J. Schmauder, 5CO.13.3, EUPVSEC 2016, Munich, June 22nd,

15 Cracks Cz mc Slope R 2 Ref-TC P mpp % 0.91 Crack1-TC P mpp % 0.90 Crack2-TC P mpp % 0.82 Slope R 2 Ref-TC P mpp % 0.82 Crack2-TC P mpp % 0.88 J. Schmauder, 5CO.13.3, EUPVSEC 2016, Munich, June 22nd,

16 Cracks Crack2-TC -Cz (top) + Crack-TC-mc (bottom) Before testing 27 cycles 222 cycles After testing J. Schmauder, 5CO.13.3, EUPVSEC 2016, Munich, June 22nd,

17 Results Results - Low shunt resistance J. Schmauder, 5CO.13.3, EUPVSEC 2016, Munich, June 22nd,

18 Results Breakdown Cz mc J. Schmauder, 5CO.13.3, EUPVSEC 2016, Munich, June 22nd,

19 Results Breakdown Self-Healing of mc breakdown module Before testing 55 cycles 82 cycles After testing Shunted spot size increases Spot borders gets sharper J. Schmauder, 5CO.13.3, EUPVSEC 2016, Munich, June 22nd,

20 Results Laser Cz mc J. Schmauder, 5CO.13.3, EUPVSEC 2016, Munich, June 22nd,

21 Results Bird Cz mc J. Schmauder, 5CO.13.3, EUPVSEC 2016, Munich, June 22nd,

22 Conclusion During TC testing of single-cell modules for >800 cycles we observed a linear degradation of % P mpp / 100 cycles due to R S increase on all modules.... we observed that finger interruption defects can electrically open and close... the Cz modules with long cracks degraded stronger ( % P mpp / 100 cycles)... R Sh of strongly shunted solar cells varies extremly and so does P mpp.... one low shunt mc-module showed self-healing from 0.2 Ω -> 4.5 Ω (2.8 W -> 3.7 W) TC is only one aspect causing aging. There are further parameters like moisture, load, UV,... J. Schmauder, 5CO.13.3, EUPVSEC 2016, Munich, June 22nd,

23 ISC booth at A2/110 Thank you! The authors gratefully acknowledge the financial support by the German Federal Ministry for Economic Affairs and Energy for the sponsorship of the research project PVScan (FKZ C) which made this work possible. J. Schmauder, 5CO.13.3, EUPVSEC 2016, Munich, June 22nd,

24 Reference sample - Cz J. Schmauder, 5CO.13.3, EUPVSEC 2016, Munich, June 22nd,

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