4,4’-Sulfonyldibenzoic Acid as a Dual-Functional Additive for Defect Passivation and Crystallization Promotion of MAPbI ₃ Toward High-Performance Perovskite Photodetectors

Perovskite films prepared using the solution method suffer from excessive defects and poor crystallinity. Carboxylic acid groups (−COOH) are widely used as additives in perovskite to passivate defects and enhance crystallization. Herein, 4,4′-sulfonyldibenzoic acid (SA) was incorporated as an additive into the perovskite precursor solution. The −COOH groups in SA enable interactions with MAPbI3. The results demonstrate that the coordination interaction between the −C=O group of −COOH and Pb2+ retards the growth of MAPbI3 films, while the hydrogen bonding between the −OH group and I– contributes to the passivation of iodine-related defects. Additionally, the introduction of SA induces compressive strain in the perovskite lattice. The SA-modified MAPbI3 photodetector achieved a maximum external quantum efficiency of 89.88%, a dark current density of 1.46 × 10–10 A cm–2, and significantly enhanced device stability.