Theoretical study on halide and mixed halide Perovskite solar cells: Effects of halide atoms on the stability and electronic properties

Increasing the stability of perovskite solar cells is one of the most important tasks in the photovoltaic industry. Thus, the structural, energetic, and electronic properties of pure CH 3 NH 3 PbI 3 and fully doped compounds (CH 3 NH 3 PbBr 3 and CH 3 NH 3 PbCl 3 ) in cubic and tetragonal phases were investigated using density functional theory calculations. We also considered the effects of mixed halide perovskites CH 3 NH 3 PbI 2 X (where X = Br and Cl) and compared their properties with CH 3 NH 3 PbI 3 . The DFT results indicate that the phase transformation from tetragonal to cubic phase decreases the band gap. The calculated results show that the X‐site ion plays a vital role in the geometrical stability and electronic levels. An increase in the band gap and a reduction in the lattice constants are more apparent in CH 3 NH 3 PbI 2 X compounds (I > Br > Cl).