Preparation of nanorod-like anatase TiO2 nanocrystals and their photovoltaic properties.

Anatase TiO2 nanocrystals with the high specific surface area were prepared by the hydrothermal treatment of anatase TiO2 sols at the temperature of 150 degrees C and above. When TiO2 sols with a lower content of TiO2 and at a relatively high pH value were hydrothermal treated, the dispersible and nanorod-like TiO2 nanocrystals were formed via the oriented attachment. The nanorod-like TiO2 nanocrystals with an aspect ratio of larger than 5 and a mean diameter of less than 7 nm were obtained in the absence of organic compounds. The as-prepared TiO2 nanocrystals were characterized with X-ray diffraction, transmission electron microscopy and BET surface area techniques. The TiO2 nanostructures were deposited on the FTO conductive glass as the anodic electrode for the dye-sensitized solar cells (DSSCs) and assembled into solar cells. The derived solar cells showed a conversion efficiency of 6.12% under 1 sun illumination of simulated sunlight and external quantum efficiency (EQE) of more than 60% at the wavelength of 550 nm. The DSSCs from the anatase nanorods has a higher open circuit voltage compared to the spherical nanocrystals.