Metal halide perovskites have become more popular for applications in solar cells and optoelectronic devices. In this study, the structural, electronic, mechanical, and optical properties of lead and lead-free metal halide cubic perovskites CsPbBr₃ and CsGeBr₃ and their Ni-doped structures have been studied using the first-principle density functional theory. Ni-doped CsGeBr₃ shows enhanced absorbance both in the visible and the ultraviolet region. The absorption edge of Ni-doped CsBBr₃ (B = Pb, Ge) shifts toward the lower energy region compared to their undoped structures. Undoped and Ni-doped lead and lead-free halides are found to have a direct bandgap, mechanical stability, and ductility. A combined analysis of the electronic, mechanical, and optical properties of these compounds suggests that lead-free perovskite CsGe_0.875Ni_0.125Br₃ is a more suitable candidate for solar cells and optoelectronic applications.

The bandgap of Cs₂AgBiBr₆ is tuned to a direct bandgap by the disordering of Ag⁺/Bi³⁺ cations, creating antisite defects. The creation of antisite defects in the sublattice of double perovskites opens a new avenue for the design of photovoltaic and optoelectronic materials.