Multi‐Site Lead Passivation via Spatial Configuration Modulation of Additives for Efficient Perovskite Solar Cells

Abstract Perovskite solar cells (PSCs) hold great promise as the next‐generation low‐cost photovoltaic technology due to their solution processability; however, this very advantage introduces intrinsic defects and microstructural imperfections, often limiting their performance and stability. Here, 4,4′‐oxydibenzenesulfonyl chloride (OBSC), featuring a flexible backbone with two sulfonyl chloride (SO 2 Cl) groups, is introduced as a bifunctional molecular additive to simultaneously passivate defects and regulate crystallization in perovskite films. The unique spatial configuration enables multi‐site coordination, strongly binding to uncoordinated lead (Pb 2+ ) via Pb−O interactions and interacting with formamidinium (FA + ) through hydrogen bonding, effectively suppressing nonradiative recombination. Concurrently, OBSC stabilizes perovskite‐solvent intermediate phases, retarding crystallization kinetics to promote the formation of high‐quality films with enlarged grains and reduced trap densities. Consequently, the optimized PSCs demonstrate a champion power conversion efficiency (PCE) of 26.39% (certified 26.03%). Furthermore, the device retains 96% of the initial PCE after 1100 h of continuous one‐sun illumination. This work demonstrates the effectiveness of bifunctional additives in simultaneously addressing defects and crystallization issues, presenting a powerful strategy for achieving high‐performance, stable perovskite photovoltaics.