Unraveling water-induced degradation mechanisms in lead-free perovskites toward durable solar cells

Despite their outstanding optoelectronic properties, lead-based perovskites suffer from poor environmental stability and intrinsic lead toxicity, which severely hinder their practical applications. Therefore, developing highly stable lead-free perovskite materials and elucidating their stability mechanisms is of great scientific and technological importance. In this work, the intrinsic water-stability mechanisms of perovskite materials are systematically investigated through a combination of experimental characterization and theoretical calculations. Molecular dynamics simulations in conjunction with dynamic contact angle measurements enabled an in-depth elucidation of the fundamental origins of perovskite structural instability under humid conditions. Furthermore, the photovoltaic performance of lead-free perovskite devices, particularly the short-circuit current density, remains insufficient. To address this limitation, an Sb-doping strategy is introduced to effectively improve the crystallinity and charge transport properties of lead-free double perovskite films, thereby significantly enhancing device performance. Long-term stability tests reveal that the devices retain over 96% of their initial power conversion efficiency after continuous operation for 1600 h. This remarkable durability underscores the excellent environmental stability of lead-free double perovskite systems and highlights their strong potential for practical photovoltaic applications.