Structural, electrochemical and optical properties of Ni doped ZnO: Experimental and theoretical investigation

Pure and Ni-doped ZnO nanorod array films were prepared by the hydrothermal method. The effects of Ni doping on the phase composition, microstructure, and optical and electro-chemical properties of ZnO were investigated. The main crystalline phase of the powders before and after Ni doping is wurtzite ZnO. The luminescent peaks are significantly reduced after Ni doping. The light transmission and is the strongest when the doping concentration is 2 %. The light absorption spectrum confirms that the band gap decreased first and then decreased with the increase of Ni2+ doping concentration. According to the M-S (Mott - Schottky) plots, the Ni-doped ZnO is an n-type semiconductor. The current density initially increases with the increased Ni doping amount, and then decreases. First-principles calculation results of nickel-doped zinc oxide show that the energy level of impurities is formed after nickel ions replace zinc ions, which causes the conduction band is shifted down and the band gap is reduced. The impurity energy level causes a slight upward shift in the valence band, which increases the band gap. The calculated results are consistent with the experimental results.