Ordered TiO₂ Nanotube Arrays on Transparent Conductive Oxide for Dye-Sensitized Solar Cells

Synthesizing highly ordered 1-D TiO 2 nanostructures directly on transparent conductive oxides (TCO), which is of key interest for fabricating front-side illuminating dye-sensitized solar cells (DSCs), has been one of the most challenging nanofabrication tasks. Here, we present a process for synthesizing vertically aligned TiO 2 nanotube arrays on TCO through a liquid-phase conversion process using ZnO nanowire arrays as a template. The resulting TiO 2 nanotube arrays can be easily integrated with the fabrication process of DSCs and lead to significantly improved photovoltaic performance compared to ZnO nanowire-based DSCs. It is also observed that the lifetime of photogenerated electrons in TiO 2 nanotubes is more than an order of magnitude larger than that in sintered TiO 2 nanoparticles. This result opens up numerous opportunities to further improve DSCs, for example, by employing solid-state electrolytes and redox mediators with faster kinetics, which otherwise would be challenging or impossible to implement by the use of nanoparticle-based DSCs.