A dye-sensitized photoelectrochemical cell has been constructed by using a TiO2 mesoporous film, a ruthenium bipyridyl derivative as photosensitizer, and a SiO2/poly(ethylene glycol)-200 (SiO2/PEG-200) nanocomposite thin film as electrolyte support. The TiO2 film has been made by hydrolysis of titanium isopropoxide in Triton X-100 reverse micelles. In the present work, emphasis has been given to the nature and the applicability of the SiO2/PEG-200 film, which has been characterized by conductivity and, mainly, time-resolved luminescence quenching techniques. It has been found that optimal cell function, is obtained with a SiO2/PEG-200 film where the PEG-200 content is about 10 wt %, a composition which is above and close to the percolation threshold for the PEG subphase.