Effect of annealing and γ-irradiation on the properties of CuInSe2 thin films

Abstract We study the structural and optical properties of CuInSe 2 thin films with the effect of annealing and γ-irradiation. CuInSe 2 thin films have been successfully deposited by spray pyrolysis technique. The as-deposited films exhibited single phase, polycrystalline and chalcopyrite structure with (112) the preferred orientation, which were confirmed by X-ray diffraction (XRD) analysis. However, selected area diffraction (SAD) analysis revealed that the films showed single crystal nature in some of the regions. An increase in the lattice constants was observed for annealed and irradiated thin films. The theoretical XRD pattern was simulated with the experimental pattern of as-deposited CuInSe 2 thin films. The optical band gaps of the films were found to increase from 0.9 to 1.0 and 1.06 eV on annealing the films in vacuum at 653 K for 1 h and γ-irradiation, respectively. In the case of irradiated samples, the second transition at 1.27 eV was observed, which was assigned to optical transition from split off valence band to the conduction band minimum (from Γ 7v 5 to Γ 6c 1 ). The Burstein–Moss shift was observed in annealed and γ-irradiated CuInSe 2 films. The Mott parameters were evaluated for CuInSe 2 thin films.