Thiocarboxylate‐Mediated Defect Suppression and I ₂ Scavenging: Achieving 22.16% Efficient and Stable CsPbI ₃ Perovskite Solar Cells

All-inorganic CsPbI₃ perovskite solar cells (PSCs) offer enhanced thermal stability compared to hybrid counterparts but suffer from interfacial defects, iodide vacancy-mediated recombination, detrimental I₂ formation, and lead leakage, limiting performance and stability. To address these challenges simultaneously, we introduce ammonium pyrrolidinedithiocarbamate (AP) as a multifunctional interfacial modifier. AP features thiocarboxylate groups that strongly chelate undercoordinated Pb²⁺, passivating defects and mitigating lead leakage, while its nitrogen-containing moieties form hydrogen bonds with I^-, suppressing iodide vacancy formation. Crucially, AP's redox-active nature chemically scavenges existing I₂ and inhibits its generation under thermal and ambient stress. These synergistic interactions promote improved film crystallinity, reduced trap density, optimized interfacial energy level alignment, and enhanced charge extraction dynamics. Consequently, AP-modified CsPbI₃ PSCs achieve significantly enhanced power conversion efficiency of 22.16% and open-circuit voltage of 1.29 V. Furthermore, the devices exhibit exceptional operational stability, retaining 97% initial efficiency after 1000 h continuous illumination under maximum power point tracking. This work demonstrates AP as a highly effective interfacial regulator and presents new insights into multifunctional molecular engineering for stable and high-efficiency all-inorganic PSCs.