Electron Transport and Recombination in Photoanode of Electrospun TiO 2 Nanotubes for Dye-Sensitized Solar Cells

The technique of coaxial electrospinning has been adopted to prepare the TiO 2 nanotubes with average inner diameter of ∼275 nm and wall thickness of ∼115 nm. The electrospun TiO 2 nanotubes possess the anatase type of crystalline structure, well-defined tubular morphology, and large aspect ratio. The dye-sensitized solar cell (DSSC) based on the TiO 2 nanotubes alone has an efficiency of 3.33% with open-circuit voltage ( V oc ) of 800 mV, short-circuit current ( J sc ) of 6.01 mA cm –2, and fill factor (FF) of 68.5%. Intriguingly, the addition of 20 wt % TiO 2 nanoparticles in the TiO 2 nanotubes improves the DSSC efficiency significantly. The charge transport and recombination in the fabricated DSSCs are characterized by the dark current, photovoltage as a function of light intensity, and transient photovoltage and photocurrent measurements. The results indicate that electrospun TiO 2 nanotubes have large diffusion coefficient and slow recombination compared to the mesoporous film of TiO 2 nanoparticles. The enhanced electron transport properties of the TiO 2 nanotubes combined with the facile and scalable preparation technique of electrospinning suggest that the electrospun TiO 2 nanotubes could be promising as photoanode material for low-cost and high-efficiency DSSCs.