Densely aligned rutile TiO2 nanorod arrays with high surface area for efficient dye-sensitized solar cells

One-dimensional (1-D) TiO2 nanorod arrays (NRAs) with large inner surface area are desired in dyesensitized solar cells (DSSCs). So far, good performance of DSSCs based on 1-D rutile TiO2 NRAs remains a challenge mainly owing to their low dye-loading ability resulting from the insufficient specific surface area of 1-D TiO2 nanostructures. In this paper, densely aligned TiO2 NRAs with tunable thickness were grown directly on transparent conductive fluorine-doped tin oxide (FTO) substrates by hydrothermal method, followed by a facile chemical etching route to further increase the specific surface area of the TiO2 NRAs. The etching treatment leads to the split of TiO2 nanorods into secondary nanorods with a reduced diameter, which markedly enlarges the inner surface area of the TiO2 NRAs. The formation of 1-D rutile TiO2 nanotube arrays (NTAs) is observed as well in the etched TiO2 films. Finally, a DSSC efficiency of 5.94% was achieved by utilizing an etched TiO2 NRA as the photoanode, which is so far the best DSSC efficiency that has been reported for the 1-D rutile TiO2 NRA films.