PHOTOELECTROCHEMICAL STUDIES OF COLLOIDAL TIO2-FILMS - THE CHARGE SEPARATION PROCESS STUDIED BY MEANS OF ACTION SPECTRA IN THE UV REGION

The charge separation process in sintered colloidal TiO2 film electrodes has been studied by means of action spectra in the UV region. The redox couple SCN-/(SCN)2- has been used in the experiments. Electrodes with different film thicknesses were studied. The results show that the current generation is most efficient close to the back contact. Monochromatic quantum efficiencies as high as 77% were registered in the UV region. The results also indicate that there exists an optimum in the overall quantum efficiency at a colloidal film thickness of approximately 4 mum, for the present system. Illumination through the back side contact gives a theoretical quantum efficiency of 100% up to a depth of 0.5 mum from the back contact. The origin of the unexpectedly high current generation in the present colloidal films is discussed.