Optical Properties of Single Layer Cu₂WSe₄ from the <i>Ab Initio</i> Bethe–Salpeter Equation Method

The binding energy of excitons is essential in assessing the suitability of materials for photovoltaic applications. This research employs first-principles calculations based on the <i>GW</i> approximation and the Bethe-Salpeter equation to explore the excitonic characteristics of a Cu₂WSe₄ monolayer. Our findings support the structural stability of this two-dimensional material and demonstrate a pronounced excitonic response. The computed binding energies for both bright and dark excitons are considerably larger than those that are generally necessary for standard photovoltaic applications. However, examination of exciton amplitude reveals a highly delocalized configuration of electron-hole pairs throughout the crystal, which may alleviate some issues related to elevated binding energies. These results highlight the excitonic properties of Cu₂WSe₄ and offer valuable insights into its potential for optoelectronic applications.