Enhancement of p-CuO/n-ZnO Heterojunction Photovoltaic Characteristics by Preparation Route and Sn Doping

Heterojunctions based on p-CuO/n-ZnO, prepared by simple methods such as spin coating, normally exhibit low photoconversion efficiency and require modification. Doping the ZnO layer with ions such as Sn4+ could be a solution. In this work, heterojunctions were prepared by two simple methods. In method 1, to prepare the CuO@ZnO junction, the n-ZnO layer was spin-coated on tin-doped indium oxide/glass substrates (ITO/glass) followed by spin coating of the p-CuO layer. In method 2, to prepare the ZnO@CuO/Cu sheet junction, the p-CuO layer was prepared by thermal oxidation of the Cu metal sheet, followed by spin coating of ZnO. In both cases, the ZnO film was doped with Sn4+ ions at 1.5% concentration by mole. The effects of Sn-doping on the structural and morphological properties of the junction were comparatively studied by X-ray diffraction and atomic force microscopy. In both preparations, doping affected the optical, electrical and photovoltaic (PV) properties. The preparation method also affected junction characteristics, as preparation method 2 showed heterojunctions with higher PV characteristics. The results show inroads to improving PV characteristics for the heterojunction based on the proper preparation method and Sn doping.