Supramolecular-Templated Thick Mesoporous Titania Films for Dye-Sensitized Solar Cells: Effect of Morphology on Performance

Highly crystallized mesoporous titania films of varying thicknesses and different morphologies, namely ordered body-centered orthorhombic and disordered wormlike mesostructure, have been successfully synthesized via a supramolecular-templated route and subsequent layer-by-layer deposition. The performance of these mesoporous films in dye-sensitized solar cells was investigated, achieving a maximum efficiency of 6-7% at the film thickness of 5-6 mum. The ordered mesoporous titania films outperformed the disordered counterpart of the same thickness in both short circuit current and efficiency. This behavior is elaborated with the dye-loading, optical, and charge-transport behavior as affected by the variation in mesoporous film morphology. The improved cell performance of the ordered mesoporous film is ascribed to the enhanced electron transport in the regularly packed titania network because of the enhanced crystalline grain connectivity. Nevertheless, the dependence of cell performance on the film morphology is weakened when the film thickness was above approximately 3.5 mum, because of the serious film cracks.