Regenerative Redox Cycling Enables Stable Tin Perovskite Photovoltaics

Tin halide perovskites (THPs) suffer from low stability due to the easy oxidation of Sn (II). Although traditional reduction strategies effectively inhibit the oxidation of Sn (II), the gradual depletion of reducing agents during continuous device operation significantly weakens their antioxidative capacity, thereby limiting the long-term stability of the device. Herein, a regenerative redox cycling strategy utilizing 4-mercaptobenzoic acid (4-MBA) is proposed. Under operational conditions, UV irradiation enables 4-MBA regeneration, which concurrently drives continuous Sn (IV)-to-Sn (II) reduction and facilitates dual-site defect passivation, significantly enhancing device efficiency and stability. Ultimately, an excellent efficiency of 15.15% is achieved and maintained 100% of the initial efficiency for 1100 h in a simulated day–night cycle maximum power point tracking (MPPT) test. This work provides a sustainable reduction strategy that effectively addresses the long-term stability issue of tin perovskite photovoltaic cells.