ZnO-nanowire-covered TiO ₂ thin-film electrodes for improving the photovoltaic properties of dye-sensitized solar cells

We report on ZnO nanowires (ZnO NWs), which were grown on the surface of a TiO ₂ thin-film electrode with zinc dihydrate acetate seeds by using thermal chemical vapor deposition. Detailed morphological properties revealed that the grown ZnO NWs fully covered the surface of the TiO ₂ thin-film electrode. The grown ZnO-NW-covered TiO ₂ thin films (ZnO NW/TiO ₂ thin-film) were used as working electrodes in dye-sensitized solar cells (DSSCs). We observed that a covering of ZnO NWs on the TiO ₂ thin-film electrodes improved the open-circuit voltage V _OC and the fill factor FF while significantly decreasing the short-circuit current density J _SC the and photovoltaic performance of the ZnO NW/TiO ₂ thin-film DSSCs compared to there for bare TiO ₂ thin-film DSSCs. The V _OC and the FF of the ZnO NW/TiO ₂ thin-film based DSSCs were enhanced by about 10 - 15% compared to the values for bare TiO ₂ thin-film DSSCs. One can attribute the enhanced V _OC and FF to the larger size of upstanding ZnO NWs on the TiO ₂ thin-film substrate, which slow surface recombination between the anode electrode and the electrolyte.