Defect Passivation and Crystallization Regulation in Wide-Bandgap Perovskites via p-Cyanobenzenesulphonamide...

Wide-bandgap (WBG) perovskites are essential for tandem photovoltaic applications, yet their performance is limited by defect-induced nonradiative recombination and suboptimal crystallization behavior. Here, we introduce p-cyanobenzenesulphonamide (p-CBSA) as a multifunctional molecular additive to regulate crystallization and passivate defect states in methylammonium-free Cs_0.15FA_0.85Pb(I_0.77Br_0.23)₃ perovskite films. Density functional theory calculations and spectroscopic analyses indicate that p-CBSA interacts strongly with undercoordinated Pb²⁺ sites through its sulfonyl and cyano functional groups, facilitating effective defect passivation. Incorporation of p-CBSA promotes improved crystallinity, enlarged grain domains, and reduced trap-states, leading to prolonged carrier lifetimes and suppressed nonradiative recombination. As a result, inverted WBG perovskite solar cells achieve a champion power conversion efficiency of 22.14%, significantly exceeding that of control devices. This work demonstrates an effective molecular additive strategy for improving film quality and photovoltaic performance in WBG perovskites relevant to tandem solar cell applications.