Enhancing the Efficiency of Perovskite Solar Cells by Bidirectional Modification of the Perovskite and Electron Transport Layer

In perovskite solar cells (PSCs), the numerous defects present on the surface of the SnO2 electron transport layer (ETL) and the bottom of the perovskite film limit their power conversion efficiency (PCE) and stability. In view of this, a bidirectional modification strategy is designed using formamidine acetate (FAAc) to passivate the defects on the SnO2 ETL surface and bottom of the perovskite simultaneously. FA+ cations act on the harmful hydroxyl groups on the SnO2 ETL surface, whereas Ac- anions act on the iodine vacancy defect at the bottom of the perovskite. Because the interface defect is well passivated by FAAc, the interfacial charge recombination is restrained. This results in a significant increase in the filling factor of the PSC to ∼0.83 and the consequent increase in PCE to 23.05%, which considerably improves the stability. Bidirectional modification technology is an effective strategy for improving the PCE and stability of PSCs.