The Impact of Bi-doped on MAPb(IxBr1-x)3 Mixed Halide Perovskite Films

Abstract Perovskite solar cells have attracted considerable attention from researchers owing to their cost-effective manufacturing processes, facilitating their suitability for commercialization. Halide perovskite such as methylammonium lead iodide (MAPbI3), methylammonium lead bromide (MAPbBr3) and other mixed halide perovskite are intensively studied as light absorber for solar cells. In order to adjust the properties of the perovskite, doping with heterovalent metal ions such as bismuth iodide, BiI3, has demonstrated notable impact on both crystal structure and optical properties. Traditionally, Bi3+ doping has been conducted primarily in single halide perovskite. However, our study explored the possibility of Bi3+ doping at a concentrations of 5% in mixed halide perovskite, specifically the mixed iodide-bromide perovskite, MAPb(IxBr1-x)3 at x = 0.2, 0.4, 0.6 and 0.8. The XRD results revealed a decrease in lattice constant upon Bi3+ doping which likely attributed to the smaller ionic radius of Bi3+ compared to Pb2+. The light absorption spectra of Bi3+ doping perovskites exhibited a significant red shift compared to the undoped samples. The presences of the key elements are confirmed by photoemission spectroscopy results. Moreover, our investigation found no notable effect on the valence band maximum upon doping. The observed red-shift presents a potential advantage for precisely adjusting the absorption edge in tandem solar cells, particularly when specific energy gaps are required.