Preferred Parallel Alignment of Sulfonamide Enables High-performance Inverted Perovskite Solar Cells

Molecule additives emerge as a highly effective strategy for enhancing the performance and stability of perovskite solar cells (PSCs), owing to their potential in suppressing intrinsic defects in perovskite. However, the influence of atomic configuration and electronic properties of additives on their passivation performance receives little attention. Here, two benzenesulfonamide derivatives, 4-carboxybenzenesulfonamide (CO-BSA) and 4-cyanobenzenesulfonamide (CN-BSA) are investigated, examining the effects of molecules with different electron‑acceptor functional groups on the defect passivation of perovskite layer and the photovoltaic properties of perovskite solar cells (PSCs. It is found that CN‑BSA and CO‑BSA preferentially adopt parallel-aligned binding orientations within the perovskite, enabling strong coordination to two neighboring undercoordinated Pb²⁺ defect sites. Meanwhile, CO‑BSA exhibits a more favorable electronic configuration than CN‑BSA, which endows the functional groups with a higher electron density that enables stronger dual-site binding with uncoordinated Pb²⁺ defects. Moreover, incorporating CO-BSA promotes the formation of perovskite films with large grain sizes, high quality, and low defect densities. Consequently, the device modified with CO-BSA achieves an efficiency of 26.53% (certified 26.31%). The encapsulated CO-BSA-based cell retains 96.1% of its initial efficiency after 1100 h of steady-state power output (SPO) measurement in air.