Double-Sided Transparent Photoanode of ZnO Nanowire Arrays Sensitized by CdS and CdSe in Photoelectrochemical Cells for Solar Hydrogen Production

A double-sided CdS and CdSe-sensitized ZnO nanowire (ZnR)/indium tin oxide (ITO) photoelectrode is fabricated using solution-based processes to improve the solar-to-hydrogen conversion efficiencies of photoelectrochemical (PEC) cells. Vertically aligned ZnR arrays were grown directly on both sides of the transparent ITO glass substrates by chemical bath deposition method and then coated with CdS and CdSe quantum dots (QDs) as the photosensitizer. This fabricated photoanode with double-sided QD sensitization enables the formation of the tandem structure as an effective heterojunction extending toward the visible spectrum and toward an effective separation of charge carriers. For PEC hydrogen generation under one-sun irradiation, the double-sided transparent photoanode of ZnR arrays with conformal QD deposition exhibited a conversion efficiency of 4.9%. Compared with that in the photoanode with layered QD aggregation, improvement in conversion efficiency was approximately 70%.