Status of UV-induced degradation in state-of-the-art solar cells and its mitigation through encapsulants

Ultraviolet (UV) degradation has recently emerged as a key reliability concern for high-efficiency solar cells. Module manufacturers have responded by modifying the solar cell architecture and/or using UV-blocking or UV-downshifting- encapsulants. To assess the impact of UV degradation on advanced photovoltaic (PV) modules and the role of encapsulants in mitigating the degradation on the state-of-the-art commercial solar cells, this work studied heterojunction thin film (HJT) and tunnel oxide passivated contact (TOPCon) devices sourced from reputed manufacturers, which were encapsulated with off-the-shelf UV-transparent, UV-blocking, or UV-downshifting materials. Accelerated UV stress testing reveals stronger degradation in HJT devices than in TOPCon. The degradation mainly reduced short-circuit current density ( J _sc ) and fill factor (FF). The reduction in J _sc can be assumed to be primarily driven by intrinsic device degradation since the variation in the UV–Vis transmission for different encapsulants following UV exposure is limited and cannot adequately explain the observed decrease in the photocurrent. UV-blocking encapsulations reduced the UV degradation, but they couldn't eliminate it. In HJT cells, higher initial efficiency was found to be positively correlated with degradation, whereas TOPCon devices showed the opposite trend. Electroluminescence (EL) imaging analysed using the OpenCV library indicated spatially inhomogeneous degradation, with dark regions intensifying after UV exposure, pointing to the uneven degradation. Overall, the results highlight the susceptibilities of HJT and TOPCon technologies to UV degradation even with current encapsulants.