UVID of TOPCon solar cells: Effect of the front passivation Al2O3 layer thickness and recovery by different processes

UV-induced degradation (UVID) has become a significant issue in tunneling oxide passivation contact (TOPCon) solar cells during field operation due to their increased sensitivity to UV radiation. The UV irradiation resistance of TOPCon solar cells passivated by Al₂O₃ layers of different thicknesses was studied. As the thickness of the Al₂O₃ film increases from 2.8 nm to 4.1 nm, the loss of maximum power (P_max) of TOPCon modules from UVID decreases from 3.24 % to 0.85 %. This indicates that increasing the thickness of the Al₂O₃ film can effectively improve the UV irradiation resistance of TOPCon solar cells. The effects of post-exposure treatments on recovery of the UV-degraded cells have also been investigated. The degraded solar cells and modules caused by UV exposure can be restored through natural sunlight and temperature-assisted electric injection treatment, which can be attributed to increased field passivation by increasing the charge density in Al₂O₃ medium. A potential mechanism for UVID and its recovery through the process of charge trapping and detrapping is proposed, which could offer an insight into the possible solutions for UVID of TOPCon modules in actual operation.