First-principles calculations of Cd-doped ZnO thin films deposited by pulse laser deposition

Zn_1?xCd_xO thin films are deposited on quartz substrate by pulse laser deposition. Their band structure and optical properties are experimentally and theoretically investigated. By varying Cd concentration, the band gap of Zn_1?xCd_xO films can be adjusted in a wide range from 3.219 eV for ZnO to 2.197 eV for Zn_0.5Cd_0.5O, which produces different emissions from ultraviolet to Kelly light in their photoluminescence spectra. Simultaneity, the electronic structure and band gap of Zn_1?xCd_xO are investigated by the density functional theory (DFT) with a combined generalized gradient approximation (GGA) plus Hubbard U approach, which precisely predicts the band-gaps of ZnO and Zn_1?xCd_xO alloys. Both the experimental results and theoretical simulation reveal that with increasing Cd concentration in Zn_1?xCd_xO alloys, their absorption coefficients in visible light range are evidently enhanced. The adjustable photoluminescence emission and enhanced visible light absorption endow Zn_1?xCd_xO alloys potential applications in optoelectronic and photocatalytic fields.