Mechanisms of UV-Induced\nDegradation in Wide-Bandgap\nPerovskite Solar Cells: Insights from Microscopic Analysis

Wide-bandgap (WBG) perovskite solar cells (PSCs) show\ngreat potential\nas the top subcells in tandem devices, yet their vulnerability to\nultraviolet (UV) radiation remains a significant barrier to commercialization.\nThis study investigates the mechanisms of UV-induced degradation in\nWBG devices and films through comprehensive failure analysis. By\nintegrating macroscopic electrical performance evaluations with detailed\nmicroscopic characterization, we focus on key aspects such as conductivity,\nleakage current pathways, defect evolution, and nanomechanical properties.\nOur results reveal that the primary causes of performance degradation\nare reductions in short-circuit current and fill factor, accompanied\nby increased hysteresis. This degradation appears to stem from a malfunctioning\njunction or increased interfacial recombination, due to high-energy\nUV photons damaging the junction interface or inducing shallow interfacial\ndefects. Our observations indicate that UV irradiation causes up to\na 90% reduction in conductivity and a 5-fold increase in leakage current,\nparticularly at grain boundaries due to interfacial defects. Negative\nions accumulate first at the grain boundaries, accompanied by a 75%\ndecrease in the Young's modulus. These findings highlight the\ncritical\nneed to stabilize the light-facing interface or strengthen the near-surface\nregion of perovskite materials to mitigate the harmful effects of\nUV exposure.