A novel TiO(2) double-layer (DL) film consisting of TiO(2) hollow spheres (HSs) as overlayer and single-crystalline TiO(2) nanorod arrays (RAs) as underlayer was designed as the photoanode of dye-sensitized solar cells (DSSCs). This new-typed TiO(2) HS/RA DL film could significantly improve the efficiency of DSSCs owing to its synergic effects, i.e. the relatively large specific surface area of TiO(2) HSs for effective dye adsorption, enhanced light harvesting capability originated from TiO(2) RA film, and rapid interfacial electron transport in one-dimensional TiO(2) nanorod arrays. The overall energy-conversion efficiency of 4.57% was achieved by the formation of TiO(2) DL film, which is 16% higher than that formed by TiO(2) HS film and far larger than that formed by TiO(2) RA film (η=0.99%). The light absorption and interfacial electron transport, which play important roles in the efficiency of DSSCs, were investigated by UV-vis absorption spectra and electrochemical impedance spectra.
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