First-Principles G0W0+BSE Calculations: Electronic and Optical Properties of Zns Monolayer

Abstract

We investigated the electronic structure and optical properties of 2D graphene-like wurtzite ZnS using first-principles calculations and many-body perturbation theory (MBPT). The structural properties were determined through first-principles calculations based on density functional theory (DFT). Structural optimization yields lattice constants of 3.81 Å for bulk and 3.76 Å for the monolayer, with Zn–S bond lengths of 2.33 Å and 2.21 Å, respectively and these values are in good agreement with experimental results. The quasiparticle band structure, excitonic, and optical properties were computed using many-body perturbation theory (MBPT) within one-shot GW (G₀W₀) approximation and the Bethe-Salpeter equation (BSE) approach, specifically G₀W₀-BSE. The electronic properties results show that ZnS sheet exhibits a direct band gap at the Γ-point, which remains unchanged as a direct semiconductor when electron-electron interactions are considered. The G₀W₀ calculations verify that monolayer ZnS is a direct bandgap material with a bandgap value of 4.106 eV, which is consistent with experimental findings. The results of optical properties with inclusion of electron-hole interactions revealed that monolayer ZnS has exciton energy of 3.66 eV with binding energy of ~0.95 eV. The strong excitonic effects in the ZnS monolayer sheet make it promising for optoelectronic device applications