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. (c) 2006 Elsevier B.V. All rights reserved.