ZnO nanorod-TiO₂-nanoparticulate electrode for dye-sensitized solar cells

Highly dense ZnO nanorods were synthesized on TiO₂- nanoparticulate coated fluorine-doped tin oxide (FTO) substrates by the chemical vapor deposition method for dye-sensitized solar cells (DSSCs). The uniformly grown ZnO nanorod layer has a thickness of ∼4 μm on the TiO ₂-nanoparticulate layer with a wurtzite structures as confirmed by the X-ray diffraction pattern. The DSSC fabricated with a ZnO nanorod/TiO ₂-nanoparticulate electrode had an overall light-to-electricity conversion efficiency η of 3.7% with a short-circuit current density J _SC of 8.12mA/cm², open-circuit voltage VOC of 0.76 V, and fill factor FF of 0.59, whereas ZnO nanowire/TiO₂-nanoparticulate- electrodebased DSSCs exhibited a low η of 1.1% with J_SC of 2.14mA/cm² and slightly high V_OC of 0.79 V. It is expected that the enhanced photovoltaic performance of the ZnO nanorod/TiO ₂-nanoparticulate electrode can be attributed to high dye loading and high light harvesting through large surface areas of ZnO nanorods incorporated with TiO₂-nanoparticulate as compared with the ZnO nanowire/TiO ₂- nanoparticulate electrode.