HC(NH2)2PbI3 as a thermally stable absorber for efficient ZnO-based perovskite solar cells

Abstract

Despite the potential of ZnO as the electron collection material for low-temperature processed perovskite solar cells (PSCs), previous investigations revealed that the CH₃NH₃PbI₃-based perovskite rapidly decomposes on ZnO at elevated temperature through a deprotonation process (base-induced reaction) that reduces thermal stability. To solve this thermal instability issue and to further enhance the photovoltaic performance, we employed a (FA)-based perovskite, i.e., FAPbI₃ as the light absorber in ZnO-based PSCs. The photovoltaic performance of the investigated FAPbI₃ solar cells was clearly dependent on both the pre-heating of the PbI₂ precursor and post-annealing of the FAPbI₃ film in the solar cell fabrication procedure. The highest power conversion efficiency of up to 16.1% was achieved under AM 1.5 simulated sunlight illumination, in which the pre-heating and post-annealing temperatures were 100 °C and 145 °C, respectively. Importantly, the thermostability of the perovskite film on ZnO was substantially improved with FAPbI₃ owing to basically the robust nature of FA compared with methylammonium (MA) in CH₃NH₃PbI₃. Moreover, FAPbI₃-based PSCs exhibited excellent photostability and small J–V hysteresis, which are all useful characteristics for further commercialization of low-temperature processed ZnO solar cells.