阿特斯&协鑫-晶硅电池LeTID衰减测试方法v6

Measurement of light and elevated temperature induced degradation (LeTID) of crystalline Si photovoltaic solar cells 2018.10.25 Participants NO. Company/Institute Participants 1 GCL System IntegrationTechnology Co., LTD Sheng Jian, Wang Wei, Wu Yanrong 2 Canadian Solar Inc. Jiang Fangdan, Zhang Daqi, Guo Suqin 3 Gsolar Power Co., Ltd Zhang Hexian 1. Background of LeTID 2. Alternative methods for LID/LeTID 3. Proposal for measurement of cell LeTID 4. Plan of next step Klaus Ramspeck et. al., “Light induced degradation of rear passivated mc-Si solar cells”, in the proceeding of 27th EUPVSEC 1. Background of LeTID ➢ mc-Si PERC solar cells exhibited a big light induced degradation at 75 ℃ ➢ The degradation does not take place at room temperature during illumination, but observed at a temperature of at least 50℃ • The defects caused LeTID is neither BO complex nor FeB complex. Remain unknown yet. 1. Background of LeTID Klaus Ramspeck et. al., “Light induced degradation of rear passivated mc-Si solar cells”, in the proceeding of 27th EUPVSEC 1. Background of LeTID 2. Alternative methods for LID/LeTID 3. Proposal for measurement of cell LeTID 4. Plan of next step 2. Alternative methods for cell LID/LeTID measurement Standard Sample Method Procedures Conditions IEC 61215-1 ED2 Modules 2-step 1st step: MQT 19.1 Initial stabilization, light soaking 2nd step: MQT 23.1 LeTID degradation, current injection 1st step: 1 sun, 5% 2. Alternative methods for cell LID/LeTID measurement • Module LeTID test in IEC 61215-1 ED2 • 1-step measurement ✓ Detection of mixed LID and LeTID ✓ How to define LeTID? ✓ Difference between LID and LeTID? • 2-step measurement ✓ Compatible with module LeTID measurement (IEC 61215-1 ED2) ✓ Get separate LID and LeTID data • 2-step measurement preferred. Considerations: 1-step or 2-step • LeTID (Light and Elevated Temperature Induced Degradation) is a misleading terminology proposed by Hanwha Q-cells. • Fundamental principle: The LID and LeTID degradation is caused by defects formation during excess minority carrier injection, either by light soaking or current injection. • Light soaking ✓ More relevant to module’s outdoor operation in practice ✓ Suitable for all kinds of crystalline solar cells ✓ Last for long time to feedback results but easy to control and measure • Current injection ✓ Compatible with module LeTID measurement (IEC 61215-1 ED2) ✓ Precise temperature control, large volume, rapid feedback, small footprint • Both light soaking and current injection can be used. Considerations: light soaking or current injection • LeTID test conditions: injection intensity, temperature, time • During the excess minority carrier injection at certain temperature, the degradation process and regeneration process happen simultaneously. • Either higher injection intensity or higher temperature will speed up both the degradation and regeneration processes. • In order to expose the maximum degradation risk, it is essential to choose proper conditions to exhibit degradation process and inhibit regeneration process. • Typically, the degradation process dominates at low injection intensity and low temperature. • However, certain degradation modes will not exhibit at low temperature, resulting in underestimation of degradation risk. This is why LeTID was brought up. Considerations: LeTID test conditions • CID test results on multi-PERC cells Dependence of degradation rate on test conditions: injection intensity, temperature Considerations: LeTID test conditions • CID test results on mono-PERC cells LeTID test results of mono-PERC cells are more sensitive to injection intensity than multi-PERC cells. CID test is better than light soaking in exposing degradation risk of mono-PERC cells. Considerations: LeTID test conditions 1. Background of LeTID 2. Alternative methods for LID/LeTID 3. Proposal for measurement of cell LeTID 4. Plan of next step 3. Proposal for measurement of cell LeTID At least 20 pcs of cells • Procedure a) I-V measurement b) 1st step light soaking for 20kWh/m2 at 45℃ c) I-V measurement d) calculate LID by difference in efficiency between a) & c) e) Light soaking for 10kWh/m2 at 80±5℃ f) I-V measurement g) Light exposure for another 5kWh/m2 in conditions of e) h) I-V measurement i) Repeat g) & h) till stabilized or reach 20kWh/m2 termination criteria j) Calculate LeTID (difference in efficiency between c) & i) Option 1 (Light Soaking): IV measurement Light exposure (10kWh/m2@80± 5℃ ) IV measurement Light exposure (5kWh/m2@80± 5℃ ) IV measurement Stable? or 20kWh/m2 N Y End Light exposure (20kWh/m2@45℃ ) IV measurement 1st step 2nd step • Procedure a) I-V measurement b) 1st step light soaking for 20kWh/m2 at 45℃ c) I-V measurement d) calculate LID by difference in efficiency between a) & c) e) 2nd step current injection Isc - Impp, 85℃ , 12 hours f) I-V measurement g) Current injection for another 12 hours in conditions of e) h) I-V measurement i) Repeat g) & h) till stabilized or reach 96 hours termination criteria j) Calculate LeTID (difference in efficiency between c) & i) Option 2 (Current Injection): I-V measurement Current injection Isc-Impp, 85℃ , 12 hours At least 20pcs of cells I-V measurement Current injection Isc-Impp, 85℃ , 12 hours I-V measurement Stabilized or 96 hours? Yes End Light soaking (20kWh/m2 @ 45℃ ) No 1st step 2nd step Termination criteria I-V measurement 3. Proposal for measurement of cell LeTID Report should include at least: • Test information (Date, name, tool, et al.) • Sample information (Number of cells, type, manufacturer, sampling criteria, et al.) • Test conditions (1st step LID condition, 2nd step LeTID condition, et al.) • Test results (LID rate, LeTID rate, whether stabilized during 2nd step, et al.) 3. Proposal for measurement of cell LeTID 1. Background of LeTID 2. Alternative methods for LID/LeTID 3. Proposal for measurement of cell LeTID 4. Plan of next step 4. Plan of next step Feedback from Busan IEC TC82 WG8 meeting: - Agree to pass NP - Agree on 2-step measurement - Suggest to collect data on equivalent between light soaking and current injection - Suggest to collect more data to determine LeTID test conditions Next step - To form Project Team - To write draft NP before end of 2018 Thanks! Q&A