Enhanced photocurrent in thin film TiO2 electrodes prepared by sol–gel method

Thin film n-type TiO2 electrodes of different thickness from 10 to 540 nm were prepared by the sol–gel method so as to investigate the effects of the film thickness on the photocurrent. Since a steep band gradient is expected to form in the thin film TiO2 electrode with thickness less than the space charge layer, such steep band bending would effectively separate the photo-generated electrons and holes, leading to an increase in the photocurrent of the thin TiO2 film electrodes. It was found that in the range of 10–540 nm in thickness, the TiO2 film electrode of 70 nm thick showed a maximum photocurrent, which was approximately six times as large as that of the electrodes of 180–540-nm thickness. This result clearly indicates that the reduction of film thickness is effective for obtaining of the efficient n-type TiO2 film electrode.