Oriented Hierarchical Porous TiO2 Nanowires on Ti Substrate: Evolution of Nanostructures for Dye-Sensitized Solar Cells

• Highly-oriented 1-D porous TiO2 nanowires on Ti foil by a facile hydrothermal method.
• Identification of hierarchical nanostructural evolution during dehydration step.
• Anatase crystallite sizes of ∼29 nm and ∼13 nm along [100] and [001], respectively.
• Enhanced dye loading by a factor of three in porous nanowires compared to nanowires.
• Optimized nanostructures by surface area, carrier lifetime, and charge transport.

Vertically-oriented and hierarchical one-dimensional TiO2 nanostructures are synthesized on Ti substrate by a facile hydrothermal method. The resulting porous nanowires, composed of highly-oriented anatase TiO2 nanocrystals, are adopted as photoelectrodes in dye-sensitized solar cells (DSSCs). The growth of the anatase crystallites resulted in ∼29 nm and ∼13 nm grains along the [100] and [001] directions, respectively. Due to the presence of truncated wedge-shape nanostructures, the cells exhibit an enhanced dye loading by more than a factor of three compared to the as-prepared nanowire DSSC. The optimum nanostructures for the light-harvesting efficiency are suggested with systematically analyzing their surface area, carrier lifetime, and charge-transport characteristics.