Controlled synthesis and photoelectrochemical properties of highly ordered TiO2nanorods

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.