The electronic and optical properties of Cu doped CdI2

Based on the density functional pseudopotential method, the electronic structures and the optical properties of CdI2 doped with Cu are investigated in detail. The calculation results indicate that the defect of Cu(Cd) exists steadily with a certain solubility. For the Cu doped CdI2, the new highly localized impurity bands induced by Cu 3d states lie just across the Fermi energy at the top of the valence band. The doping of Cu induces reduction of band gap of CdI2; red shifts are revealed in both the imaginary part of dielectric function and the absorption spectra corresponding to the change in band gaps. Moreover, the study of the reflection spectrum and the loss function shows that the doped Cu is responsible for the increased reflection peak intensity and the red shift of the plasma resonant frequency of CdI2.