Impact of oxygen vacancies on the structural, electronic, and optical properties of Cu2O and nitrogen-doped Cu2O for optoelectronic applications: a first-principles study

Abstract

This study utilizes Density Functional Theory (DFT) within the Quantum ESPRESSO framework to explore the effects of oxygen vacancies and nitrogen doping on the electronic structure and optical properties of cuprous oxide (Cu₂O). Pristine Cu₂O, an intrinsic p-type semiconductor, typically exhibits a direct band gap. Introducing an oxygen vacancy in the absence of a dopant broadens the band structure, leading to both direct and indirect band gap characteristics. In contrast, nitrogen doping transforms the band gap into a direct one, significantly reducing it from 1.97 eV to 1.09 eV, which deviates from previous findings due to potential variations in the initial state of the Cu₂O host crystal. Furthermore, spin-polarization effects indicate spin-dependent behaviour within the material. The study also examines the absorption properties of pristine, defective, and nitrogen-doped Cu₂O systems using the complex dielectric function. The results show distinct absorption peaks and transitions, with nitrogen-doped Cu₂O exhibiting strong absorption in the visible light range, underscoring its potential for solar cell applications.