Photoelectrochemical performance of multiple semiconductors (CdS/CdSe/ZnS) cosensitized TiO 2 photoelectrodes

The morphology of TiO2 nanotubes with nanowires directly formed on top (designed as TiO2 NTWs) would be a promising nanostructure in fabricating photoelectrochemical solar cells for its advantages in charge separation, electronic transport, and light harvesting. In this study, a TiO2 NTWs array film was prepared by a simple anodization method. The formation of CdS, CdSe, and ZnS quantum dots (QDs) sensitized TiO2 NTWs photoelectrode was carried out by successive ionic layer adsorption. The as-prepared materials were characterized by scanning electron microscopy, high-resolution transmission electron microscopy, and X-ray diffraction. Our results indicate that the nanocrystals have effectively covered both inner and outer surfaces of TiO2 NTWs array. The interfacial structure of QDs/TiO2 was also investigated for the first time in our experiment, and the growth interface when annealed to 300 C was verified. Under AM 1.5G illumination, we found the photoelectrodes have an optimum short-circuit photocurrent density of 4.30 mA/cm(2) and corresponding energy conversation efficiency of 2.408%, which is 28 times higher than that of a bare TiO2 NTWs array. The excellent photoelectrochemical properties of our photoanodes suggest that the TiO2 NTWs array films (2.6-2.8 mu m) cosensitized by CdS, CdSe, and ZnS nanoclusters have potential applications in solar cells.