Photoelectrochemical Performance of Multiple Semiconductors (CdS/CdSe/ZnS) Cosensitized TiO₂ Photoelectrodes

Abstract

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/cm² 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 μm) cosensitized by CdS, CdSe, and ZnS nanoclusters have potential applications in solar cells