Photosensitization of TiO 2 nanoparticulate thin film electrodes by CdS nanoparticles

. Surface photovoltage spectra (SPS) measurements of TiO 2 show that a large surface state density is present on the TiO 2 nanoparticles and these surface states can be efficiently decreased by sensitization using CdS nanoparticles as well as by suitable heat treatment. The photoelectrochemical behavior of the bare TiO 2 thin film indicates that the mechanism of photoelectron transport is controlled by the trapping/detrapping properties of surface states within the thin films. The slow photocurrent response upon the illumination can be explained by the trap saturation effect. For a TiO 2 nanoparticulate thin film sensitized using CdS nanoparticles, the slow photocurrent response disappears and the steady-state photocurrent increases drastically, which suggests that photosensitization can decrease the effect of surface states on photocurrent response.