Synthesis of ZnO@TiO2 core–shell long nanowire arrays and their application on dye-sensitized solar cells

Long ZnO nanowire arrays (NAs) grown on fluorine-doped tin oxide (FTO) glasses have been synthesized via a facile hydrothermal method without refreshing the reaction solution and applied as the precursor. By adjusting growth conditions, ZnO NAs with tunable lengths can be achieved. A nanocomposite made of ZnO nanowire core and TiO2 shell was further realized by a novel “fast-dip-coating” method conducted in a Ti(OC4H9)4-dissolved ethanol solution. The formed ZnO@TiO2 core–shell NAs on FTO substrates were applied as electrodes for dye sensitized solar cells (DSSCs). It is found that both the TiO2 coating and NAs length play important roles in the enhancement of photoelectric conversion efficiency (PCE) of DSSCs. When the length of ZnO@TiO2 NAs reaches up to 14 μm, the electrode can exhibit a maximum PCE as high as 3.80%, which is 2.6 times higher than that of pure ZnO NAs.