Dual-Action Self-Assembled Monolayer Synchronizes SnO 2 /Perovskite Interface and Crystallization for Superior Perovskite Photovoltaics

Despite the remarkable advancement of metal halide perovskite solar cells (PSCs) achieving power conversion efficiencies (PCEs) reaching 27.3%, suppressing nonradiative recombination at critical interfaces remains pivotal to unlocking their full performance potential and ensuring operational longevity. A promising solution lies in interfacial engineering, as exemplified by self-assembled molecular interlayers designed for defect passivation. Here, we propose hydroxylamine-O-sulfonic acid (HOSA) as a multifunctional molecular bridge at the tin oxide (SnO 2 )/perovskite buried interface. Experimental and computational analyses reveal that HOSA’s sulfonic acid (−SO 3 H) and amine (−NH 2 ) groups anchor to SnO 2 via ester linkages and coordinate with undercoordinated Pb 2+ defects in the perovskite, respectively. This dual-interaction mechanism simultaneously passivates interfacial traps, enhances charge extraction kinetics, and promotes perovskite crystallization with reduced lattice strain. Consequently, the HOSA-modified devices achieve a champion PCE of 24.22%, surpassing the reference cells (22.34%) while delivering enhanced durability: unencapsulated devices retain 78% of initial efficiency under continuous 1 sun illumination (500 h) and 71% after thermal aging (65 °C, N 2, 1000 h). This work underscores the efficacy of rationally engineered molecular interlayers in harmonizing interfacial energetics and defect dynamics for high-performance perovskite photovoltaics.