High-performance photovoltaic perovskite layers fabricated through intramolecular exchange

Abstract

The band gap of formamidinium lead iodide (FAPbI₃) perovskites allows broader absorption of the solar spectrum relative to conventional methylammonium lead iodide (MAPbI₃). Because the optoelectronic properties of perovskite films are closely related to film quality, deposition of dense and uniform films is crucial for fabricating high-performance perovskite solar cells (PSCs). We report an approach for depositing high-quality FAPbI₃ films, involving FAPbI₃ crystallization by the direct intramolecular exchange of dimethylsulfoxide (DMSO) molecules intercalated in PbI₂ with formamidinium iodide. This process produces FAPbI₃ films with (111)-preferred crystallographic orientation, large-grained dense microstructures, and flat surfaces without residual PbI₂. Using films prepared by this technique, we fabricated FAPbI₃-based PSCs with maximum power conversion efficiency greater than 20%.