Fabrication, Photoelectric Property And Application Of Titanium Dioxide Nanotube Arrays

One-dimensional (1D) wide band-gap TiO2nanotubes have favorable chemical stability and photoelectric properties, and it is an excellent carrier for charge separation and transport. The TiO2nanotubes have been widely applied in photocatalysis, sensors and dye-sensitized solar cells etc areas. The key point of improving its performance and expanding its application is to change and modifiy its nano-structure. Based on this research background, we fabricated regularly arranged two-layer TiO2nanotube arrays, and developed a low-cost, convenient operation and environment friendly method to obtain large-scale, non-curing and highly ordered TiO2nanotube arrays film. The practical application of the two kinds of nanotubes structure in photovoltage devices area has been extensively studied and discussed.1. Highly ordered and regularly arranged TiO2nanotube arrays ware fabricated on the Ti foil surface by a two-step anodic method in ethylene glycol electrolyte containing0.25wt%NH4F at50V constant-voltage. We can get a two-layer nanotubes structure when the anodiztaion time is controlled between15～40mins, and the tubes become ordered for further extending the oxide time. Firstly, the length of the nanotube arrays increases rapidly with the anodization time and then the growth rate gradually slows down with further increasing the anoization time. The mechanism of anodization time changing with tube length growth and the tube formation are discussed. It gives us experimental and theoretical support for deeply comprehending the formation mechanism of the nanotubes, and it is also good for us to control the morphology and structure of the nanotube.2. Large-scale, various thickness TiO2nanotube arrays film was obtained through the reaction force between the Ti foil and H2O2solution making the TiO2separated from substrate. This method can produce non-curling free-standing TiO2film as thin as15.5μm and the largest area can reach up to14cm2. The DSSCs based on this kind of large-scale and free-stranding TiO2film is good for front-side illumination mode, and it will avoid light dissipation when using the opposite illumination mode. The front-side illumination mode has an significance practical significant to improve the photoelectric conversion efficiency of the DSSCs based on TiO2nanotube arrays electrode. 3. The photovoltaic performance of the DSSCs assembled by the as-prepared two kinds of nanotubes structure has been deeply investigated. Firstly, the single layer nanotubes film was transferred to the fluorine-doped tin oxide (FTO) conductive glass substrates and strongly adhered onto it with a layer of home made TiO2sol to form "sandwich"structure DSSCs, and a power conversion efficiency of4.12%was obtained without any surface treatement, which is much higher than the other cells sharing the same structure reported in the papers. At the same time, not only the effect of the nanotubes length to the dye-adhered efficiency and cell performance, but also the other relative factors and mechanism have been studied. Secondly, in the two-layer structure section, p-type Cu2O nanowires were deposited into n-type TiO2nanotube arrays to form a p-n heterojunction core-shell structure pure inorganic solar cells, and the related impact factor were investigated.4. To further improve the photovoltaic performance, the TiCl4was used to modify the surface of the photoanode. The dye absorption density and banding energy of the nanotube arrays treated with TiCl4have been increased by expanding the surface area. Compared with the untreated cells, the power conversion efficiency improved by12%. Meanwhile, we developed a chemical method to fabricate Pt counter-electrode. It enhanced the photocatalytic activity for the electrolyte and decreased the body resistance of the whole system as well. Based on this improvement, the power conversion efficiency improved by19%with a4.90%rise. More important, the light transmittance of the counter electrode reaching80%has shown a great potential in solar cells based on back-side illumination mode and flexibility solar cells with wide application in many areas.On the basis of the ever existing outstanding chemical and photoelectricity of the DSSCs taking TiO2nanotubes as the photoanode, considering the state and problems of the present research, we further reviewed and analyzed the factors deserving in-depth research as well as further improving the battle performance. This study plays a significant role in deepening the comprehension of TiO2nanotubes, improving the efficiency of DSSCs as well as expanding the application fields of TiO2nanotubes. The follow-up research of the present study was also prospected.