Controlled synthesis and photoelectrochemical properties of highly ordered TiO2 nanorods

Abstract

Highly ordered TiO2 nanorods (NRs) were grown directly on fluorine doped tin oxide (FTO) substrate by a single step hydrothermal synthesis at 150 °C. The morphology of TiO2 was significantly altered by changing the solvents of ethanol/deionized (DI) water as the precursor solutions. With ethanol/DI water (80 : 20 v/v) as solvent, the highly ordered tetragonal TiO2 NRs were achieved on FTO substrates with the average lengths of ∼2–4 μm and diameters ∼50–70 nm respectively. While, the round headed and distorted hexagonal TiO2 NRs were formed with ethanol/DI water ratios of 50 : 50 v/v and 0 : 100 v/v as the precursor solutions respectively. The grown TiO2 NRs possessed the anatase phase with typical tetragonal crystal structures. XPS studies evidenced that the grown TiO2 NRs exhibited the O : Ti stoichiometric ratio of 2 : 1 with lower impurities of the carbon species. The grown TiO2 NRs thin film substrates were applied as photoanodes for efficient dye-sensitized solar cells (DSSCs). A solar-to-electricity conversion efficiency of ∼3.2% was achieved by DSSC, fabricated with highly ordered tetragonal TiO2 NRs photoanode, whereas DSSC with the distorted hexagonal TiO2 NRs photoanode showed inferior overall conversion efficiency (∼1.08%). The improved photovoltaic performance was credited to the highly ordered morphology of the TiO2 NRs, which executed the high charge collection and the transfer of electrons at the interfaces of the TiO2 NRs photoanode and the electrolyte layer.