Nonempirical hybrid functionals for band gaps of inorganic metal-halide perovskites

Abstract

Nonempirical hybrid functionals are investigated for band-gap predictions of inorganic metal-halide perovskites belonging to the class $\mathrm{Cs}B{X}_{3}$, with $B$ = Ge, Sn, Pb and $X$ = Cl, Br, I. We consider both global and range-separated hybrid functionals and determine the parameters through two different schemes. The first scheme is based on the static screening response of the material and thus yields dielectric-dependent hybrid functionals. The second scheme defines the hybrid functionals through the enforcement of Koopmans' condition for localized defect states. We also carry out quasiparticle self-consistent $GW$ calculations with vertex corrections to establish state-of-the-art references. For the investigated class of materials, dielectric-dependent functionals and those fulfilling Koopmans' condition yield band gaps of comparable accuracy $(\ensuremath{\sim}0.2$ eV), but the former only require calculations for the primitive unit cell and are less subject to the specifics of the material.