Titanium Dioxide Thin Films with Controlled Stoichiometry for Photoelectrochemical Systems

The electrical resistivity of thin film metal oxide photoanodes in the photoelectrochemical cells, PEC, for hydrogen generation, the importance of which should not be neglected in the design and construction of water-splitting devices, is found to be affected by the departure from stoichiometric composition and film thickness. Here, we propose to use TiO2/ITO photoanodes for photoelectrochemical cells. The TiO2−x thin films with x indicating a departure from the stoichiometric composition have been prepared by dc magnetron sputtering with the deposition rate controlled by the optical emission spectroscopy, OES. Photoanode properties were determined by scanning electron microscopy, SEM, atomic force mocroscopy, AFM, Raman spectroscopy, transmittance and reflectance measurements over uv/vis/nir wavelength ranges, impedance spectroscopy, Mott–Schottky plots, and photocurrent versus voltage dependence in the dark and under white light illumination. The contributions of the charge carrier concentration and mobility to the enhanced photocurrent of the PEC have been determined and correlated to the varying film stoichiometry and thickness, respectively.