First-principles investigation of electronic structure, optical, mechanical properties, and strain effects of double perovskite Cs2LiSbX6(X = Cl, Br, I)

Abstract

We conducted an in-depth investigation on the lattice structure, optoelectronic properties, and elastic constants of halide double perovskite Cs₂LiSbX₆ (X = Cl, Br, I) based on first principles calculations. The computed elastic and mechanical properties demonstrate that all three materials exhibit mechanical stability, alongside excellent ductility and anisotropic behavior. In addition, these three materials Cs₂LiSbCl₆, Cs₂LiSbBr₆, and Cs₂LiSbI₆ exhibit indirect band gaps of 3.65 eV, 3.05 eV and 2.29 V, respectively, and are classified as wide bandgap materials. The optical characteristics of Cs₂LiSbX₆ were evaluated through the computation of several key parameters: the real component of the dielectric function (ε₁(ω)), the imaginary component of the dielectric function (ε₂(ω)), the refractive index (n(ω)), and the absorption coefficient (α(ω)). In addition, the strain engineering, spanning from −6 % to 6 %, reveals that compressive strain(tensile strain) narrows(widens) the bandgap, leading to a blueshift(redshift) in the absorption edge. These findings provide theoretical support for adjusting the bandgaps of Cs₂LiSbX₆ perovskites.