Achieving Defect Passivation and Oriented Crystallization Regulation at the SnO 2 /Perovskite Interface via Molecular Bridging

Abstract Buried interface defects between the SnO 2 electron transport layer (ETL) and the perovskite layer severely limit the efficiency, hysteresis, and stability of SnO 2 ‐based perovskite solar cells (PSCs). In this study, 3‐Isothioureidopropionic acid (ATPN) is introduced as a molecular bridge at the buried perovskite interface, effectively passivating interface defects and regulating the oriented growth of perovskite crystals. The carboxyl (‐COOH) groups of ATPN passivate dangling Sn bonds on SnO 2 , reducing surface oxygen vacancies and facilitating charge extraction and transport. Meanwhile, the imino (‐C═NH) and amino (‐NH 2 ) groups of ATPN effectively passivate undercoordinated Pb 2+ and I − ions in the perovskite, reducing interfacial defects and optimizing energy level alignment. In situ crystallization studies reveal that ATPN‐mediated modulation extends the recrystallization process of the perovskite, promoting the formation of larger grains during fabrication. Additionally, this strategy induces a highly preferred out‐of‐plane (100) crystal orientation by eliminating energy barriers, thus enhancing carrier extraction and transport. A champion ATPN‐treated PSC achieved a power conversion efficiency (PCE) of 24.06%, compared to 22.15% for the control device. After 1920 h of aging in a nitrogen atmosphere, the ATPN‐modified device retained 90.14% of its initial PCE, while the unmodified device retained only 68.32%.