Fabrication of Nanosheet/Nestlike Nanoarray Hierarchical TiO<sub>2</sub> Film for Dye-Sensitized Solar Cell

A hierarchical configuration of TiO2 nanoarray film, comprising a nestlike TiO2 nanoarray layer integrated with a nanosheet network overlayer, was constructed. The hierarchical TiO2 film was obtained by the post-hydrothermal treatment with NaOH solution on hydrothermally synthesized TiO2-derived nanostructured arrays grown on fluorine-doped tin oxide substrate (FTO). The TiO2 films were characterized by field-emission scanning electron microscope (FE-SEM), X-ray diffraction (XRD), ultraviolet-visible (UV-Vis) diffuse reflectance spectroscopy, and absorbance spectroscopy. FE-SEM shows that the hierarchical TiO2 film with a thickness of 1.5 mu m is composed of a nanosheet overlayer (similar to 0.2 mu m height) and the nestlike nanoarray layer (similar to 1.3 mu m height). XRD patterns display that the TiO2 films have pure anatase phase structure. UV-Vis spectra reveal enhanced light scattering and dye adsorption ability of the hierarchical TiO2 film. For the dye-sensitized solar cell (DSSC) based on the nanosheet/nestlike nanoarray hierarchical TiO2 film, a short-circuit current (J(sc)) of 7.79 mA.cm(-2), open-circuit voltage (V-oc) of 0.80 V, fill factor (FF) of 0.40, and photoelectric conversion efficiency (eta) of 2.48% are achieved. Within the dye-sensitized solar cell, the photoelectric conversion efficiency of the hierarchical TiO2 film was nearly ten times higher than that of nanostructured array film.