Tight-binding study of the structure of the electronic energy band of the quaternary solid solutions series CuIn

We report on the electronic properties of the solid solutions series CuIn1−xAlxTe2 using the tight-binding (TB) method and the virtual crystal approximation (VCA) for different values of amounts of Al, considering the ideal case and that with distortions. The parameters TB and VCA were determined, which allow the best fit of the theoretical results to the linear behavior reported in the literature of the band gap as a function of x. Using these parameters, we calculate the structure of the energy bands, obtaining that this material is a direct semiconductor at Γ for all the concentrations. In addition, discrimination of the orbitals in the bands was carried out, finding the existence of s orbitals of the cations Cu and (In,Al), and s and p orbitals of the anion Te in the lower part of the conduction band, which indicates the possibility of bonding between the cations and the anions, which would explain the chemical stability of the compound under strong illumination and high temperatures, making it a useful material for implementation in solar panels