Sodium Benzoate Enabled Dual-Functional Defect Engineering for Stable and Broadband Tin-Based Perovskite Photodetectors

Lead-free tin-based perovskites have garnered significant research interest due to their low toxicity and remarkable optoelectronic properties. However, the oxidation of Sn2+ ions remains a critical challenge that hinders their further advancement. In this work, a Na+-containing additive, sodium benzoate (NaBz), is incorporated into PEA0.1FA0.9SnI3 perovskite thin films via a one-step solution spin-coating process to enhance their photoresponse. The optimized lateral photodetectors exhibit a peak responsivity (R) of 0.456 A·W-1, nearly five times higher than that of the unmodified control device (0.092 A·W-1). Comprehensive investigations reveal that NaBz significantly improves the oxidation resistance, moisture tolerance, and operational stability of the perovskite films. The carboxylate (−COO–) group in NaBz can act as a Lewis base to coordinate with undercoordinated Sn2+ ions, effectively passivating defect sites, while the presence of Na+ may influence the local chemical environment of halide species and defect-related sites, potentially contributing to the regulation of halide-ion migration and ionic redistribution. These complementary effects provide a simple and effective approach to improving the stability and photoresponse of lead-free tin-based perovskite photodetectors.