Environmentally Benign and Efficient Ag2S-ZnO Nanowires as Photoanodes for Solar Cells: Comparison with CdS-ZnO Nanowires

In this work, we develop a low-temperature, facile solution reaction route for the fabrication of quantum-dot-sensitized solar cells (QDSSCs) containing Ag2S-ZnO nanowires (NWs), simultaneously ensuring low manufacturing costs and environmental safety. For comparison, a CdS-ZnO NW photoanode was also prepared using the layer-by-layer growth method. Ultraviolet photoelectron spectroscopy analysis revealed type-II band alignments for the band structures of both photoanodes which facilitate electron transfer/collection. Compared to CdS-ZnO QDSSCs, Ag2S-ZnO QDSSCs exhibit a considerably higher short-circuit current density (Jsc) and a strongly enhanced light-harvesting efficiency, but lower open-circuit voltages (Voc), resulting in almost the same power-conversion efficiency of 1.2%. Through this work, we demonstrate Ag2S as an efficient quantum-dot-sensitizing material that has the potential to replace Cd-based sensitizers for eco-friendly applications.