Improvement in electrical properties of sol–gel-derived In-doped ZnO thin film by electron beam treatment

Abstract: In-doped ZnO thin films were prepared by a sol–gel spin coating method. Since several issues with In doping have been reported, such as degradation of crystallinity and deterioration of electrical resistivity at high In-doping levels, co-doping with Ga and electron beam treatment was demonstrated in this study. When In dopant was added to the ZnO thin film at 0.5 mol%, it increased the carrier concentration, thereby reducing the resistivity of the film. In contrast, further doping by Ga in the presence of In did not significantly change the electrical properties. When electron beam treatment was conducted on ZnO films, the optical band gap was increased and the carrier concentration and mobility were increased. In particular, a 0.5 mol% In-doped ZnO that received electron beam treatment at 2 keV exhibited an electrical resistivity as low as 4.8 × 10⁻² Ω cm, while 57.1 Ω cm was obtained from the pristine ZnO thin film. When the ZnO films were applied to crystalline Si solar cells, conversion efficiency significantly increased from 10.37 % for the cell with pristine ZnO thin film to 11.45 % with the In-doped and electron beam-treated ZnO thin film.