First-Principles Calculation of Electronic Structure and Optical Properties of CuInGaSe_2/CuInAlSe_2

It presents the structural and electronic characterization of CuInGaSe2(CIGS) and CuInAlSe2(CIAS).The fully-relaxed calculations have been made using the density functional theory,and structure constant matches the experimental values.The density of states,adsorption constant,reflectivity,dielectric constant and refractive index are also calculated.The results show that the chalcopyrite CIGS and CIAS are direct band gap semiconductors with band gaps 1.34 eV,1.50 eV respectively.Comparatively,CIAS have higher adsorption and dielectric values with lower reflectivity at high photon energies,which is promising for high efficiency solar cells.