Effect of ZnO Seed Layer and TiO2 Coating Treatments on Aligned TiO2/ZnO Nanostructures for Dye-Sensitized Solar Cells

A chemical bath deposition (CBD) method was applied to grow zinc oxide nanorod arrays on transparent conductive oxides acting as templates for the synthesis of TiO2/ZnO nanostructures (TiO2/ZNR) followed by HCl etching, and then these nanostructures were assembled as anodes in dye-sensitized solar cells. The ZnO nanorods, predominantly grew with good crystallinity along c-axis, exhibit wurtzite structure with smooth surface. Etching of the TiO2/ZNR by HCl changes the most preferential crystal plane of ZnO from (002) to (100) and significantly increases the atomic ratio of Ti/Zn. Optical absorption measurements indicate a band gap energy of 3.1 eV for ZNR and TiO2/ZNR. Increasing the spin coating time (SCT) of TiO2 on ZNR increases the PL intensity. The seed layer number (SLN) of ZnO exerts moderate influence on the photo-to-electricity conversion and an optimum SLN was observed for this study.