High-Fill-Factor Perovskite Solar Cells via Pseudohalide Salt Modification of the Substrate to Mitigate Nonradiative Recombination at the Interface.

The utilization of the sol-gel method for fabricating planar SnO as the electron transport layer (ETL) induces numerous defects on the SnO layer surface and perovskite film bottom, causing considerable deterioration of the device performance. Conventional inorganic salt-doped SnO precursor solutions used for passivation may cause incomplete substrate coverage due to the presence of inorganic salt crystals, further degrading the device performance. Here, a substrate modification approach involving the pretreatment of a fluorine-doped SnO (FTO) substrate with NHPF is proposed. The interaction between PF ions and the FTO substrate enhances SnO film quality; excess PF ions decrease the number of defects on the film surface. NH ions react with an -OH stabilizing agent in the SnO solution and are eliminated during annealing. The combined effects suppress nonradiative recombination and ion migration at the ETL-perovskite interface. The corresponding high-quality perovskite solar cells (PSCs) exhibit a fill factor of ∼0.825; PSC efficiency increases from 19.59% to 22.32%.