CdS quantum dots-sensitized TiO₂ nanorod array on transparent conductive glass photoelectrodes

An oriented single-crystalline TiO₂ nanorod or wire array on transparent conductive substrates would be the most desirable nanostructure in preparing photoelectrochemical solar cells because of its efficient charge separation and transport properties as well as superior light harvesting efficiency. In this study, a TiO₂ nanorod array film grown directly on transparent conductive glass (FTO) was prepared by a simple hydrothermal method. The formation of CdS quantum dots (QDs) on the vertically aligned TiO₂ nanorods photoelectrode was carried out by chemical bath deposition. The as-prepared materials were characterized by scanning electron microscopy, transmission electron microscopy (TEM), high-resolution TEM, and X-ray diffraction. The results indicate that CdS QDs with a diameter smaller than 10 nm are uniformly covered on the surface of the single-crystalline TiO₂ nanorods. Under AM 1.5 G illumination, the photoelectrode was found with a photocurrent intensity of 5.778 mA/cm² at a potential of 0 V versus Ag/AgCl and an open-circuit photovoltage of 1.292 V versus Ag/AgCl. The photocurrent is 28.6 times higher than that of a bare TiO₂ nanorod array, and the photoelectrochemical properties are comparable to those of a CdS QDs-sensitized TiO₂ nanotube array, suggesting that the CdS QDs-sensitized TiO₂ nanorod array on FTO photoelectrodes has a potential application in solar cells.