Effects of Metal Doping on the Structural, Electrical, and Optical Properties of Spin-Coated Nanocrystalline ZnO

In this work, we systematically investigate the effects of metal doping on the structural, electrical, and optical properties of spin-coated nanocrystalline ZnO thin films prepared by a simple acetate-based solution process. The incorporation of different metal dopants significantly modified the crystallographic, electrical, and photoluminescence properties of ZnO. Doping with alkali metals enhanced the photoluminescence efficiency and enabled amplified spontaneous emission, whereas Mg was the only dopant that produced a pronounced blue shift in the photoluminescence spectra. Lithium-doped ZnO exhibited a strong concentration-dependent electrical behavior, producing highly conductive n-type ZnO at a 1% doping level and p-type conductivity at an 8% concentration. Strong n-type conductivity was also achieved using low concentrations of Li and Na and higher concentrations of Al. In contrast, Fe-, Ni-, Cu-, and Pb-doped ZnO exhibited a substantial reduction in electrical conductivity accompanied by strong photoluminescence quenching, indicating enhanced defect-related carrier compensation. These results demonstrate that metal doping provides an effective approach for tailoring the structural, optical, and electrical properties of ZnO and offers a versatile route toward engineering ZnO-based layers for optoelectronic devices, transparent conductive contacts, photodetectors, solar cells, and ultraviolet laser applications.