Photosensitization of ZnO nanowire-based electrodes using one-step hydrothermally synthesized CdSe/CdS (core/shell) sensitizer

One-step assembled CdSe/CdS (core/shell) quantum dots (QDs) were deposited onto ZnO nanowires (NWs) and characterized for their structure, morphology and optical analyses. As deposited ZnO NWs array were wurtzite in structure. During a single hydrothermal cycle a layer of ~4nm CdSe/CdS QDs was formed onto ZnO NWs and overgrowth evidenced with an additional 2-5 layers due to which, (a) absorbance density, and (b) Raman Shift of 1LO mode (from 286cm^-1 to 296cm^-1) increased and (c) the photoluminescence intensity of the near band-edge emission peak at ~379nm decreased. Due to more accumulation of CdSe/CdS, photoelectrochemical cells of ZnO-based photoelectrodes designed for 1-4 cycles of CdSe/CdS onto indium-tin-oxide substrate demonstrated increasing power conversion efficiency trend from 0.18% to 1.29% whereas, for 5th cycle power conversion efficiency, due to an increased series resistance, decreased to 1.12% on account of an accumulation of several QDs.