Pseudo-halide anions engineering of FAPbI3 surface and SnO2/ FAPbI3 heterostructure

Recently, introducing pseudo-halide anions to form mixed-anion perovskites has been found to significantly improve the quality of perovskite films, providing an effective strategy for realizing stable and efficient perovskite solar cells. Herein, using density functional theory (DFT) calculations, we explore the possibilities to improve the stability of FAPbI3 surface and the charge transfer properties of SnO2/FAPbI3 heterostructure by doping pseudo-halide anions. We first study the thermodynamic stability of the perovskite surfaces and find that pseudo-halide-doped FAPbI3 surfaces are more stable than pristine FAPbI3 surface. All the SnO2/perovskite interfaces form type-II band alignment that can facilitate interfacial electron-hole separation under illumination. Moreover, the bandgap and work function of FAPbI3 surface can be tuned via using pseudo-halide anions, lowering the conduction band offsets of SnO2/perovskite heterostructures. Photo-generated electrons can be easily transferred from perovskites to SnO2, which will be favorable for solar cell applications. In addition, pseudo-halide-doped surfaces can also enhance light absorption properties, compared to pristine FAPbI3 surface. Our DFT calculations indicate that pseudo-halide-doped perovskites can serve as promising photovoltaic materials for optimizing the stability and optoelectronic properties of photoactive layers.