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.