A single-molecular bridge for simultaneously passivating dual-interface defects to fabricate high-efficiency and...

Buried interface defects exist between the electron transport layer (ETL) and the perovskite (PVK) active layer, which severely limit the efficiency, hysteresis, and stability of SnO₂-based perovskite solar cells (PSCs). In this study, we introduced L-2-amino-5-ureidovaleric acid (LAUA) between SnO₂ and the perovskite film, which is a bidirectional modifier with carboxyl (-COOH), amino (-NH₂), and urea (-NH-CO-NH₂) groups at its two ends. The -COOH groups can effectively bind to the uncoordinated Sn⁴⁺ and dangling hydroxyl groups (-OH) on the SnO₂ surface, thereby optimizing the interface morphology and energy level alignment. On the other end, the -NH₂ groups can undergo specific interactions with Pb²⁺ in MAPbI₃, which delay the crystallization rate and passivate Pb-related defects at the buried interface. Additionally, the urea groups are capable of interacting with uncoordinated Pb²⁺ and I^-. These synergistic effects promote the efficient extraction of interfacial carriers, reduce interface-induced energy loss, suppress the residual of excess PbI₂ at grain boundaries, optimize film surface flatness, and ultimately achieve the balanced transport of charge carriers. Consequently, the LAUA-modified device exhibited a champion PCE of 26.21%, featuring enhanced long-term stability.