FAPbBr3 perovskite solar cells with VOC values over 1.5 V by controlled crystal growth using tetramethylenesulfoxide

Abstract

Perovskite solar cells (PSCs) capable of an open-circuit voltage (V_OC) of over 1.5 V were fabricated based on a formamidinium lead-bromide (FAPbBr₃) perovskite absorber film prepared by a sequential deposition procedure using a dimethylsulfoxide (DMSO) and tetramethylenesulfoxide (TMSO) mixed solvent. A PbBr₂ film formed from a precursor PbBr₂ solution with the DMSO–TMSO mixed solvent was reacted with FABr to conversion into an FAPbBr₃ film. The mixed solvent-based PbBr₂ film exhibited an amorphous-like phase containing a PbBr₂–TMSO complex, which led to the formation of an FAPbBr₃ film possessing high crystallinity and a uniform thick absorber layer compared with the pristine PbBr₂ film prepared with pure DMSO solvent. With a bandgap of 2.1 eV, FAPbBr₃-based PSCs prepared via the solution process with the PbBr₂–TMSO complex exhibited a high V_OC value of up to 1.55 V and a power conversion efficiency of 7.8% on device fabrication using an Li-treated mesoporous TiO₂ as an electron transport layer with a 5 × 5 mm² cell active area.