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

The facile oxidation of Sn2+ to Sn4+ 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 Pb0 from the photolysis of perovskite reacts with Sn4+ to regenerate Pb2+ and Sn2+ spontaneously. Given the sluggish redox reaction kinetics, V3+/V2+ 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 V3+/V2+ 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. A V3+/V2+ redox couple was developed to accelerate the spontaneous redox reactions between Sn4+ and Pb0, enabling the perpetual regeneration of Sn2+ and Pb2+ for self-healing tin-lead mixed perovskites under light soaking. The target vanadium-containing tin-lead mixed perovskite (V-Sn-Pb) solar cells showed substantially improved durability over 1000 hours under operation.+image