Synthesis of TiO₂ nanotube/ZnO nanorod hybrid nanocomposite photoanodes for dye-sensitized solar cells

TiO₂ nanotube/ZnO nanorod hybrid nanocomposite (ZTN) photoanodes were synthesized, characterized and assembled as dye-sensitized solar cells (DSSCs) at optimum conditions for improving photovoltaic efficiency. The self-organized and high ordered TiO₂ nanotube arrays were growth on titanium foil by anodic oxidation as a substrate for ZnO decoration by hydrothermal method. Zinc nitrate hexahydrate and hexamethylenetetramine precursor concentrations were varied to designate the optimum ZnO decoration density for enhanced photoconversion efficiency. XRD, FESEM and XPS results showed that the crystal structure, morphology, elemental composition and density of ZnO nanorods on the surface of TiO₂ nanotubes are very sensitive to ZnO precursor concentrations. It is found that, the highest overall efficiency of DSSC based on ZTN photoanode was measured 1.8% for precursor concentration of 60 mM which was more than double compared to DSSC based on bare-TiO₂ nanotubes (0.8%). The improvement of DSSC efficiency originates from suppressing the recombination rate and decreasing the charge transfer resistance due to synergetic effect between TiO₂ nanotubes and ZnO nanorods.