Preparation Of Nanocrystalline Titanium Dioxide And Their Application In Dye-Sensitized Solar Cells

In this thesis, we focused our attention on the research work of preparation of TiO2 nanocrystallites with different morphologies including nanocrystalline particles, spheres and nanorods and their applications in dye-sensitized solar cells. The main contents and results are as follows:1) TiO2 nanocrystalline particles/spheres were prepared through sol-gel followed by hydrothermal method using tetrabutyl titanate as precursor. The size of TiO2 nanocrystalline particles are about 20-30 nm, TiO2 spheres are up to 2 microns in diameter. Both of them are pure anatase. TiO2 film electrodes were fabricated with these nanocrystalline particles/spheres. Light scattering and electron transport in the TiO2 film electrodes have been investigated. The light scattering property of TiO2 sphere film was stronger than that of nanocrystalline particle film, which was due to the large-size of TiO2 spheres. The electronic diffusion rate of TiO2 sphere film electrode was a little better than that of nanocrystalline particle film electrode. DSSC fabricated with TiO2 particle film electrode showed a photoelectrical conversion efficiency of 7.26%. DSSC fabricated with TiO2 sphere film electrode showed a higher fill factor and a conversion efficiency of 7.88%.2) Anatase TiO2 nanorods were synthesized by the same way as above except that the introduction of tetramethyl ammonium hydroxide (TMAH). The synthesized TiO2 nanorods were proved to be pure anatase single crystal materials. Sizes of TiO2 nanorods could be controlled with diameter ranging from 50 to 150 nm and length ranging from 150 to 1000 nm. TMAH acted as structure-directing agent on the formation of TiO2 nanorods. Furthermore, hydrolysis or alcoholysis process of titanate had a major impact on the final morphology of TiO2. The so-prepared TiO2 nanorods showed excellent light scattering and electron transfer properties, and both of the properties were directly related with their sizes, the longer the rod length, the stronger these properties.3) A double-layer film electrode comprised with nanocrystalline particle film as bottom layer and nanorod film as upper layer has been designed. Nanocrystalline particle film layer adsorbed most of the sensitized dye, while nanorods film layer acted as light scattering centers. This structure integrated both the advantages of small particles and nanorods and eventually a photoelectric conversion efficiency of 9.23% has been achieved for DSSC based on such double-layer film electrode.