First-principles studies on the electronic and optical properties of CuAlSe2 and CuAl5Se8

The electronic structure, dielectric function, absorption coefficient, and reflectivity of two polycrystalline semiconductors CuAlSe2 and CuAl5Se8 are studied using the density functional theory within the generalized gradient approximation. There are different peaks in the spectra of the imaginary part of the dielectric function. The transitions between the valence bands and conduction bands are discussed at length. In addition, we also notice that the reduced absorption coefficient and reflectivity near band-edge in Cu-poor CuAlSe2 are closely related to a reduction of the density of states near the valence band maximum.

► We study the electronic and optical properties of CuAlSe2 and CuAl5Se8 in theory. ► These materials are the direct band-gap compounds. ► We discuss the optical transitions between the VBs and CBs in ε2(ω) spectrum in detail. ► Cu deficiency results in a drop of the absorption and reflectivity for CuAl5Se8.