Ultrahigh efficient single-crystalline TiO2 nanorod photoconductors

Photoconductive gain and normalized gain, which determine the device and material properties on photoconduction, respectively, have been defined for single-crystalline titanium dioxide (TiO2) nanorods (NRs) with various diameter sizes. The gain values of the NR photodetectors can reach 10(5) easily at a low bias of 0.1 V. By excluding the contributions of experimental parameters, the optimal normalized gain of the indirect-bandgap TiO2 NRs at 5.4 x 10(-5) m(2)V(-1) is comparable with that estimated from the direct-bandgap ZnO nanowires. The average normalized gain value at 3.3 +/- 2.2 x 10(-5) m(2)V(-1) obtained from eight individual TiO2 NRs with diameters ranging from 120 to 1250 nm is also over three orders of magnitude higher than the polycrystalline nanotube counterpart. The results demonstrate the superior photoconductivity efficiency in boundary-free titania one-dimensional nanostructure, which is crucial for ultraviolet photodetector, dye-sensitized solar cell, and photochemical device applications. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3694926]