TiO2 nanorod arrays grown from a mixed acid medium for efficient dye-sensitized solar cells

A series of oriented rutile TiO2 nanorod-array films are in-situ grown on fluorine-doped tin oxide (FTO) coated glass substrates from a mixed acid solution containing titanium tetraisopropoxide (TTIP), hydrochloric acid (HCl), acetic acid (HOAc), and water (H2O) by means of hydrothermal reaction at 150 °C. The effect of HOAc in the titania growth solution on the structure and micro-morphology of TiO2 nanorod array films, as well as the photoelectric conversion properties in dye-sensitized solar cells (DSSCs) has been fully investigated. It is found that HOAc can facilitate the formation of uniform, dense, and vertically oriented TiO2 nanorods and hence improves the dye adsorption, electron diffusion coefficient, and the photovoltaic performance of DSSCs, typically in short-circuit photocurrent and power conversion efficiency. A power conversion efficiency of 4.03% has been achieved on a DSSC based on a 2.3 µm-long nanorod array film obtained from a mixed acid solution with the TTIP:HCl:HOAc:H2O ratio of 0.8:4:8:8 by volume.