Nanocrystalline anatase TiO2 derived from a titanate-directed route for dye-sensitized solar cells

TiO2 nanoparticles used in numerous applications are generally prepared from the sol–gel method. Because of the competitive, rather than exclusive, formation of the three TiO2 polymorphs, anatase, brookite and rutile, in the sol–gel synthesis, phase-pure nanoparticles can hardly be obtained. The present work demonstrates a unique route, alternative to the conventional sol–gel method, to prepare high-purity anatase TiO2 colloids, which can be deposited as electrodes for dye-sensitized solar cells (DSSCs) to facilitate electron transport and avoid charge recombination. In this developed route, a titanate with its TiO6 octahedra arranged in a zigzag configuration, which is also a characteristic feature of anatase TiO2, is produced as an intermediate. Raman analysis shows that a phase-pure anatase TiO2 colloid is prepared from the developed route, while the TiO2 derived from the sol–gel at the same temperature is predominantly composed of anatase with the presence of a minute amount of rutile and brookite. Because of the high-purity in anatase phase, the TiO2 colloid derived from the titanate-directed route is shown to constitute a mesoporous film exhibiting high performance in a dye-sensitized solar cell.