Green Dual-Interface Passivation with Succinic Anhydride Derivation for High-Performance Perovskite Solar Cells

Interfacial trap states at the electron-transport layer (ETL)/perovskite and perovskite/hole-transport layer (HTL) junctions remain major bottlenecks to efficiency and stability in perovskite solar cells (PSCs). Here, we present a one-step, green dual-interface passivation strategy using succinic-anhydride derivatives: succinic acid, generated by aqueous hydrolysis, at the SnO2/perovskite interface, and monoethyl succinate, formed via ethanol-driven esterification, at the perovskite/CuInS2 (CIS) interface. Optimized concentrations (3 mg mL–1 bottom, 2 mg mL–1 top) deliver a champion power conversion efficiency (PCE) of 18.76%, with Voc = 1.1 V, Jsc = 24.18 mA cm–2, and FF = 72.0%. The diode ideality factor decreases from 2.25 to 1.26, while dark leakage currents are suppressed by ∼57%. Devices retain >90% of their initial steady-state power output after 264 h of ambient storage. Our analysis indicates that succinic acid neutralizes defect states at the buried SnO2/perovskite interface, whereas monoethyl succinate targets surface Pb2+ and iodide vacancies at the perovskite/HTL junction. This dual passivation reduces trap density, suppresses nonradiative recombination, and improves carrier extraction, resulting in higher efficiency and enhanced device stability.