Conveniently fabricated heterojunction ZnO/TiO ₂ electrodes using TiO ₂ nanotube arrays for dye-sensitized solar cells

TiO ₂ nanotube arrays with an inner average pore diameter of 83 nm and a length of 14 μm are grown on Ti foils by electrochemical anodization in ammonium fluoride-water-glycerol solution. ZnO is introduced into the TiO ₂ nanotube arrays by a convenient electrodeposition technique. ZnO/TiO ₂ nanocomposites supported on Ti substrate are used as the photo-anode electrode for dye-sensitized solar cells (DSSCs). The morphology, structure and electrochemical properties are investigated using field-emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, UV-vis diffusion reflection spectroscopy, X-ray photoelectron spectroscopy and cyclic voltammetry measurements. It is found that ZnO have been embedded in the TiO ₂ nanotube arrays, and changed some photoelectric properties. The conversion efficiency of the dye-sensitized solar cells is more than doubled, compared with that of bare TiO ₂ nanotube arrays with deposited 60 min. This improvement comes from the synergetic effect between ZnO and TiO ₂, which increases dye absorption, electron transport and electron lifetime.