Single-Molecular Bridge for Simultaneously Passivates Dual-Interface Defects to Fabricate High-Efficiency and Stable Perovskite Solar Cells

Abstract

Abstract: Perovskite solar cells (PSCs) based on SnO2 electron transport layers (ETL) have been widely developed due to their excellent power conversion efficiency (PCE). In this study, we introduced L-2-Amino-5-ureidovaleric acid (LAUA) between the 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 passivates 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 device modified with LAUA achieved a high PCE of 26.21%. In terms of stability, the unencapsulated modified device also showed improved performance. Specifically, at room temperature with a relative humidity of 20–30%, the unencapsulated LAUA-optimized device retained 88% of its initial efficiency after 1800 hours.