Nanocrystalline anatase TiO 2 derived from a titanate-directed route for dye-sensitized solar cells

Abstract

TiO 2 nanoparticles used in numerous applications are generally prepared from the sol–gel method. Because of the competitive, rather than exclusive, formation of the three TiO 2 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 TiO 2 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 TiO 6 octahedra arranged in a zigzag configuration, which is also a characteristic feature of anatase TiO 2, is produced as an intermediate. Raman analysis shows that a phase-pure anatase TiO 2 colloid is prepared from the developed route, while the TiO 2 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 TiO 2 colloid derived from the titanate-directed route is shown to constitute a mesoporous film exhibiting high performance in a dye-sensitized solar cell.