Accelerated Redox Reactions Enable Stable Tin‐Lead Mixed Perovskite Solar Cells

Abstract The facile oxidation of Sn 2+ to Sn 4+ poses an inherent challenge that limits the efficiency and stability of tin‐lead mixed (Sn−Pb) perovskite solar cells (PSCs) and all‐perovskite tandem devices. In this work, we discover the sustainable redox reactions enabling self‐healing Sn−Pb perovskites, where their intractable oxidation degradation can be recovered to their original state under light soaking. Quantitative and operando spectroscopies are used to investigate the redox chemistry, revealing that metallic Pb 0 from the photolysis of perovskite reacts with Sn 4+ to regenerate Pb 2+ and Sn 2+ spontaneously. Given the sluggish redox reaction kinetics, V 3+ /V 2+ ionic pair is designed as an effective redox shuttle to accelerate the recovery of Sn−Pb perovskites from oxidation. The target Sn−Pb PSCs enabled by V 3+ /V 2+ ionic pair deliver an improved power conversion efficiency (PCE) of 21.22 % and excellent device lifespan, retaining nearly 90 % of its initial PCE after maximum power point tracking under light for 1,000 hours.