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

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 (SO₂Cl) 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 (Pb²⁺) 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.