Preparation And Properties Of Dye - Sensitized Solar Cells By TiO 2

With the development of social economy and scientific technology, the demand of energy has greatly increased. However, the burning of traditional fossil fuels have caused tremendous damage and even threatened human lives. As a non-polluting renewable energy with large reserves, solar energy is widespread concerned around the world. Among the existing solar cells, dye sensitized solar cell (DSSC) has attracted more and more researchers because of its simple preparation process, low investment costs and little environmental pollution. Photoanode is a key component of dye sensitized solar cell, which directly affects the dye adsorption capacity, electron transport, light-capturing ability and finally the energy conversion efficiency. TiO2nanocrystalline particle film, which has a high specific surface area, is mostly used now. But the contact interface between the particles, making the electron at the interface seriously recombine with each other and lengthening transmission paths of electrons, which directly affects the final conversion efficiency. In addition, the common preparation methods of TiO2nanoparticle film are applied by screen printing method and scraping method, leading to the insufficient bonding strength between FTO and film. They limit the development of these kinds of preparation technology. In comparison, one-dimensional structure TiO2films can effectively separate charge and provide a direct path for electron transfer process. Meanwhile, the one-dimensional ordered array films can reduce the electron recombination at interface and improve cell efficiency. However, the surface area and specific surface area of conventional single layer arrays are low, which directly affects the amount of dye adsorption. Thus, the conversion efficiency is always low. Therefore, in this paper, etching method is used to change the morphology of films and to improve the conversion efficiency of DSSC. The main contents are as follows:Firstly, the as-prepared nanorod arrays are etched by hydrochloric acid. During the etching process, the control variable method is used to research the relevance among reaction temperature, reaction time, concentration of hydrochloric acid and film properties. The results show that the etching reaction proceeded fastest at the initial stage and then gradually slowed down. Raising the reaction temperature could also increase the etching rate of the reaction. Increasing the concentration of hydrochloric acid has the greatest impact on the photoelectric performance of film. Longer time, higher temperature and concentration of hydrochloric acid would make the films drop off the FTO. The conversion efficiency improved from1%to1.85%during the etching process.Secondly, in order to make the etching reaction become more sufficient, the TiO2seed layer was introduced to improve the binding ability of the films. At the same time, the bilayer structure films were prepared by increasing the concentration of precursor and changing the setting angle of the FTO. Then these bilayer films were also etched with hydrochloric acid. Combine with SEM, it is found that the nanorod clusters at top layer gradually transferred to nanotube clusters, while the nanorod arrays at bottom layer became nanowire arrays with smaller diameters, during the etching process. The conversion efficiency of DSSC increased from0.94%to4.13%after etching process. The reasons of different morphology changes at two layers are rutile phase nanorods’anisotropic and the different interfacial energy between the outside wall of nanorods of clusters and inside nano wires which compose of nanorods.Finally, in order to further improve the conversion efficiency of the DSSC, TiCl4treatment was applied. It was found that with the immersion time increasing, Villous TiO2was obtained on the surface of the nanotube clusters, which enhanced the surface area, thereby increasing the short circuit current density. Compared with the films before etch, the conversion efficiency reached to5.25%. When lengthened the immersion time, the villous TiO2became branched structure. Though the surface area had improved, a large number of interface contact would make serious charge recombination, which reduced the short-circuit current density.