Photoconduction Properties in Single-Crystalline Titanium Dioxide Nanorods with Ultrahigh Normalized Gain

We report on a systematic photoconductivity (PC) study on the individual titanium dioxide (TiO 2 ) nanorods (NRs) with single-crystalline quality. The photoconductive gains (device-oriented parameter) and their corresponding normalized gains (material-oriented parameter) of the TiO 2 NRs have been defined and compared. The quantitative results show that the indirect-bandgap TiO 2 NR exhibits a competeable photoconduction efficiency with the maximal (saturation) normalized gain (Γ n ) at 2 × 10 –4 m 2 V –1 in comparison to the direct-bandgap zinc oxide (ZnO) nanowires (Γ n ∼ 1.2 × 10 –4 m 2 V –1 ). In addition, the maximal normalized gain is also over 4 orders of magnitude higher than that reported for the polycrystalline nanotube counterpart. The photoconduction mechanism is also proposed for the highly efficient photoconduction properties in this titania nanostructure. The results demonstrate the potential of an ultrasensitive ultraviolet photodetector using TiO 2 NRs and the superior efficiency for charge transport in boundary-free titania one-dimensional nanostructures, which is crucial for dye-sensitized solar cell and photochemical device applications.