Enhanced Stability of All-Inorganic Tin–Lead Perovskite Solar Cells via Additive Engineering

All-inorganic tin–lead halide perovskites (CsPb x Sn 1– x I 3 ) are promising absorber materials for next-generation photovoltaics due to their near-ideal bandgaps (∼1.3–1.4 eV) and favorable optoelectronic characteristics. Their practical application, however, is limited by intrinsic instabilities, including Sn 2+ oxidation, halide migration, and phase transitions. Here, we introduce an additive engineering approach using dimethylammonium iodide (DMAI) to address these challenges. DMAI simultaneously passivates deep-level defects, inhibits Sn 2+ oxidation, reduces iodide migration, and improves moisture resistance, thereby enhancing environmental stability. CsPb x Sn 1– x I 3 films treated with DMAI maintain stable perovskite phases in air and exhibit improved optoelectronic properties. Devices fabricated with these films achieve power conversion efficiencies up to 14.2%, compared to 8.9% for untreated controls, and retain more than 94% of their initial performance after 3000 h of inert storage. This work highlights additive-driven stabilization as a pathway toward durable, high-efficiency all-inorganic perovskite solar cells.