Modification of a TiO₂ photoanode by using Cr-doped TiO ₂ with an influence on the photovoltaic efficiency of a dye-sensitized solar cell

This work reports on the preparation of Cr-doped TiO₂ (Cr-TiO₂) and its utilization in the photoanode of a dye-sensitized solar cell (DSSC). Pure TiO₂ and 10% Cr-TiO₂ sols were individually obtained via hydrolysis followed by a hydrothermal process at 250 °C for 12 h. The TiO₂ sol was first coated on a fluorine-doped tin oxide (FTO) substrate using a polymer binder and sintered at 500 °C for 30 min. The Cr-TiO₂ sol was then deposited on the TiO₂ layer through the same procedure, thus forming two different layers on the substrate. We found that the photovoltaic efficiency was improved by ca. 18.3% when the double layer was adopted as the photoanode of a DSSC instead of only the TiO₂ layer. We assume that this improvement was caused by the repression of electron recombination occurring in the double layer. Further characterizations were carried out to clarify the function of the double layer.