Synergistic Passivation Effect via a Bidentate Anchoring Molecule between the Perovskite Layer and Electron Transport Layer for Perovskite Solar Cells

Abstract

In this study, we introduce a dual-side interface engineering approach utilizing 2,3-diaminobenzoic acid (DABA) as a bilateral passivation layer to enhance the photoelectric property of perovskite solar cells (PSCs). DABA features a carboxyl group (−COOH) on one side of the benzene ring and two amino groups (−NH2) on the other. The −COOH anchors Sn4+ of a SnO2 electron transport layer (ETL) and effectively passivates defects of the ETL by coordinating with undercoordinated Sn4+ ions. The passivation enhances the electrical conductivity and electron mobility of the ETL. In addition, the conduction band of the ETL upshifts for optimized energy-level alignment after the passivation. For the surface passivation of the upper layer, through its interaction with undercoordinated Pb2+ at the buried interface, the −NH2 group enables effective defect passivation and the suppression of nonradiative recombination within the perovskite (PVK) film. This synergistic effect further modulates the buried interface structure, significantly promoting the growth of a high-quality PVK film with enlarged grains and improving its charge-extraction capability. Consequently, the power conversion efficiency (PCE) of PSCs after DABA modification was effectively improved. The stability of the device has also been improved after 340 h of aging in ambient air (20 °C, 25% RH).