Electron Transport and Recombination in Photoanode of Electrospun TiO2 Nanotubes for Dye-Sensitized Solar Cells

The technique of coaxial electrospinning has been adopted to prepare the TiO2 nanotubes with average inner diameter of similar to 275 nm and wall thickness of similar to 115 nm. The electrospun TiO2 nanotubes possess the anatase type of crystalline structure, welldefined tubular morphology, and large aspect ratio. The dye-sensitized solar cell (DSSC) based on the TiO2 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 % TiO2 nanoparticles in the TiO2 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 TiO2 nanotubes have large diffusion coefficient and slow recombination compared to the mesoporous film of TiO2 nanoparticles. The enhanced electron transport properties of the TiO2 nanotubes combined with the facile and scalable preparation technique of electrospinning suggest that the electrospun TiO2 nanotubes could be promising as photoanode material for low-cost and high-efficiency DSSCs.