Study of optical properties of CuI from first principles*

Copper(I) Iodide (CuI) is a wide band gap semiconductor that is a good candidate to be used as a transparent conductive material. In this study, we used first-principles simulations to explore the optical properties of CuI. The Perdew-Burke-Ernzerhof (PBE) functional was used to determine the influence of spin-orbit coupling on the electronic band structure and optical properties of CuI. From density functional theory (DFT) simulations of the band structure and optical spectra, we conclude that the effect of spin-orbit coupling is small, but not insignificant. To account for the excitonic effects in CuI, we solved the Bethe-Salpeter Equation (BSE) calculation for the optical polarization function. The resulting optical spectrum agrees very well with experiment across a photon energy range up to 4 eV. However, at energies greater than 4 eV, differences on the order of 0.5 eV arise. We believe this can be explained by spin-orbit coupling, screening effects, and quasiparticle effects. The future of this study is to optically pump the system and explore the real time dynamics to understand the fundamental aspects of relaxation.