Mechanisms of UV-Induced Degradation in Wide-Bandgap Perovskite Solar Cells: Insights from Microscopic Analysis

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