Band Gap Engineering of Cs3Bi2I9 Perovskites with Trivalent Atoms Using a Dual Metal Cation

Ternary metal halides (A(3)X(2)I(9)) have attracted considerable interest because they have good:stability and reduced toxicity compared with Pb-based halide perovskites. The main issue with A(3)X(2)I(9) is their band gap, which is relatively large for use in a single junction solar cell (1.9-2.2 eV for the Cs3Bi2I9). This theoretical study found that the band gap of Cs3Bi2I9 can be successfully modulated by using dual metal cations, i.e., by forming. Cs3Bi2I9 (X: trivalent cation). Among the various trivalent atoms, investigated, In and Ga showed very promising band gap modulation behaviors. Additionally, the indirect band gap of Cs3Bi2I9 can be changed into a direct nand gap.