Improved Electron Diffusion Coefficient in Electrospun TiO₂ Nanowires

Abstract

TiO2 nanowires with a diameter of ∼150 nm, length of ∼3−4 μm, and aspect ratio of 10:1, were prepared by ultrasonically dispersing electrospun continuous nanofibers in monocarboxylic acids. The resulting pastes were used for making nanowire films on conducting glass substrates with thicknesses in the range of 500 nm to 100 μm, good adhesion, and high nanowire packing. These films were used to fabricate dye-sensitized solar cells using the D131 dye and the iodide/triiodide electrolyte. Transient photocurrent measurements showed a high electron diffusion coefficient in those nanowire films. The measured diffusion coefficient in those TiO2 nanowires was orders of magnitude higher than that observed in nanoparticles under similar experimental conditions. The charge-transport mechanism in the nanowire sample is discussed in support with the measured open-circuit voltage decay curves.