| Dye-sensitized solar cell (DSSC) is a novel photochemical solar cell. The electron-collecting layer in a DSSC is typically a lOμm thick nanocrystalline film comprised of a three dimensional network of interconnected15-20nm sized nanoparticles. Compared with TiO2nanoparticles, TiO2nanorod/wire/tube arrays offer direct pathways for electrons and can increase the electron transport rate, which improves the performance of the device. Due to their ability to constrain the movement of electrons and photons in one direction, TiO2-based materials with one-dimensional structures have been intensively investigated.Nanostructured TiO2has been widely investigated in the field of electrochemical energy storage. It owns a very small volume expansion ratio (3%) upon Li ion intercalation/extraction, and exhibits good cyclic stability. Well-ordered TiO2nanowire arrays offer a large internal surface area and excellent pathways for Li-ion to transfer between interfaces. So it is an excellent material employed as a stable anode for lithium ion batteries. However, the theoretical specific capacity of TiO2is very low (168mA h g-1for Lio0.5TiO2), restricting its use in Li ion batteries. High capacity anode materials combined with TiO2can improve its specific capacity.In this thesis, solvothermal synthesis conditions of TiO2nanowire arrays are systematically researched, and the as-prepared TiO2nanowire array and its complexes are applied in the field of DSSC and lithium-ion battery, the main research work carried out are as follows:(1) Highly oriented TiO2nanowire arrays were synthesized directly on the transparent conducting substrate by solvothermal procedure without any template. The as prepared TNAs have been systematically studied at various reaction conditions, the essential structure of the synthesized TNAs is single nanowires, and several nanowires bunch together to form a larger secondary structure, namely a bunch of nanowires. FTO substrate should be placed with conducting surface facing down to eliminate the interference of homogeneous nucleation of TiO2in solution. Well ordered, vertically oriented TiO2nanowire arrays can be achieved at appropriate conditions (2h,4h,6h;180℃,200℃,220℃), and the nanowires grow along the (002) direction. The nanowire width, the width of a bunch of nanowires and the nanowire length increases with longer reaction time and higher temperature. In reaction period too short or temperature too low, only bulks of nanorods in not regular shape can be obtained. The overall photoelectric conversion efficiency of the cells comprised of TNAs prepared at180℃for2h reaches as high as1.64%, and the value reduces to0.93%for longer nanowires prepared for6h because of diminishing of effectual surface area. Further improvement is expected by fabricating titania arrays comprised of thin nanowires separating apart from each other.(2) TiO2nanowire arrays were synthesized directly on the transparent conducting substrate by solvothermal procedure without any template. The morphology and vertical orientation of the as-prepared TNAs have been detailedly studied upon various substrate modifications. The essential structure of the synthesized TNAs is single nanowires, and several nanowires bundle together to form a larger secondary structure, namely a nanowire bundle. TNA grown on unpretreated FTO glass tends to peel off from the substrate so it’s not workable for solar cell use. The peeling problem can be resolved by modification of a TiO2nanoparticle layer. TNAs on substrate modified by6nm and25nm particles suffer from a bad vertical orientation, and corresponding solar cell exhibits relatively low conversion efficiency. By using the substrate pretreated by a drop of0.05M TiCl4isopropanol solution, the crystal vertical orientation and conversion efficiency improves significantly. As to the substrate modified by being immersed in0.05M TiCl4aqueous solution, the as-prepared TNA owns excellent vertical orientation and thus shows a photoelectric conversion efficiency as high as1.81%.(3) A novel material of TiO2nanowire array/Sn composite has been fabricated directly on titanium substrate through a facile method. This nanostructure provides good electrical contacts between the active materials and the current collector without using additives and conductive agents. The TNA-Li2O framework ensures excellent cycling stability of the composite structure, and an appropriate amount of tin brings high volumetric capacity and outstanding rate capability. By introducing component of Sn, a reversible volumetric capacity increases significantly to1610mA h cm-3for the initial cycle. The unique TiO2-Li2O framework accommodate Sn and lessen its mechanical strain during cycling. After300cycles, charge capacity remains1006mA h cm-3, which is4times of that of bare TNA. The crystal growth direction of TNA and also electrical conductivity of Sn component facilitate rapid discharge/charge performance. Our study has therefore opened the great possibility for rutile TiO2nanowire arrays combined with other high capacity materials to apply in many fields of Li-ion batteries.(4) A novel material of Si/TiO2nanowire array composite has been fabricated directly on titanium substrate through a facile method. This nanostructure provides good electrical contacts between the active materials and the current collector without using additives and conductive agents. The TNA framework ensures excellent cycling stability of the composite structure, and an appropriate amount of Si brings high specific capacity and good rate capability. The as-prepared Si includes two phases of amorphous and nanocrystalline. Composites with different Si mass percentages are researched, by introducing75%Si component, the reversible capacity increases significantly to1480mA h g-1for the initial cycle. The TiO2framework accommodate Si and lessen its mechanical strain during cycling. After200cycles, charge capacity remains as high as802.3mA hg-1. The crystal growth direction of TNA and also electrical conductivity of Si component facilitate rapid discharge/charge performance.
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