Fabrication of Nanosheet/Nestlike Nanoarray Hierarchical TiO_2 Film for Dye-Sensitized Solar Cell

A hierarchical configuration of TiO_2 nanoarray film,comprising a nestlike TiO_2 nanoarray layer integrated with a nanosheet network overlayer,was constructed.The hierarchical TiO_2 film was obtained by the post-hydrothermal treatment with NaOH solution on hydrothermally synthesized TiO_2-derived nanostructured arrays grown on fluorine-doped tin oxide substrate(FTO).The TiO_2 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 TiO_2 film with a thickness of 1.5 μm is composed of a nanosheet overlayer(~0.2 μm height) and the nestlike nanoarray layer(~1.3 μm height).XRD patterns display that the TiO_2 films have pure anatase phase structure.UV-Vis spectra reveal enhanced light scattering and dye adsorption ability of the hierarchical TiO_2 film.For the dye-sensitized solar cell(DSSC) based on the nanosheet/nestlike nanoarray hierarchical TiO_2 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(η) of 2.48% are achieved.Within the dye-sensitized solar cell,the photoelectric conversion efficiency of the hierarchical TiO_2 film was nearly ten times higher than that of nanostructured array film