Electronic surface state of TiO2 electrode doped with transition metals, studied with cluster model and DV-Xα method

The surface electronic structure of rutile TiO2 used for a photo-catalyst and an electrode of the dye-sensitized solar cell, was calculated by the DV-Xα method. The electrical properties of mesoporous TiO2 electrode are dependent on the surface levels introduced by a high surface area. In this study, the electronic state of bulk TiO2 structure was calculated using the (Ti15O56)52− model and the surface state of (1 1 0) plane was calculated using the (Ti11O34)24−–O∗ (O∗=surface oxygen) model, respectively. In addition to the surface state of pure TiO2, the surface dopant levels introduced by the doping of transition metals in Ti4+ ion site were also calculated using the MTi11O34–O∗ (M=transition metal) model. With calculated results, the variation of surface levels including dopant levels was discussed in association with electrode properties.