Nanostructured Mesoporous Thick Films of Titania for Dye-Sensitized Solar Cells

Abstract

For energy harvesting, such as in dye-sensitized solar cells, thick films of nanostructured mesoporous titania are inevitably required. Although various mesoporous thin films, i.e., film thickness below 300 nm, such as those of TiO2 and SiO2, have been widely investigated via a supramolecular templating approach in the past decade, little progress has been made with thick films, i.e., film thickness of at least several micrometers. In order to develop the desperately wanted thick films of mesoporous nanostructure for titania, we have successfully modified the supramolecular templating approach, where the highly crystallized mesoporous titania thick films of varying thicknesses and different morphologies are realized, resulting in the formation of highly ordered body-centered orthorhombic and disordered wormlike mesostructures. The performance of these mesoporous films in dye-sensitized solar cells has been investigated, achieving a maximum efficiency of ~7% at the film thickness of ~6 μm. The highly ordered mesoporous titania film outperforms the disordered counterpart of the same thickness in both short circuit current and efficiency. The improved cell performance of the ordered mesoporous film is shown to arise from the enhanced electron transport in the regularly packed titania network due to the enhanced crystalline grain connectivity.