Tunable Electronic and Optical Properties of ZnO/Germanene Heterostructure for Solar Cells and Near Infrared Photodetector: A First-Principles Calculations

Abstract

In this study, we investigated the electronic and optical properties of ZnO/germanene heterostructures using density functional theory (DFT) combined with the many-body G₀W₀ and Bethe–Salpeter equation (BSE) approaches. The quasiparticle band gaps of bulk and monolayer ZnO were calculated to be 3.20 eV and 3.79 eV, respectively, consistent with experimental values. For the ZnO/germanene heterostructure, the band gap decreased from 0.60 eV to 0.09 eV as the interlayer distance increased from 2.0 Å to 3.5 Å. The optical absorption spectra revealed strong absorption in the visible region, especially at an interlayer distance of 2.0 Å, where the optical gap was 0.6 eV. These results indicate that the ZnO/germanene heterostructure is a promising candidate for optoelectronic and solar cell applications due to its tunable band gap and efficient visible light absorption.