Doping And Surface Modification On Nanocrystalline TiO₂ Semiconductor

The solar energy is abundant and infinite and is one of the best ways to solve the energy crisis. Therefore, as an important part of the dye-sensitized solar cells, TiO₂ thin film electrode has attracted the wide attention. However, as one semiconductor material of dye-sensitized solar cell, TiO₂ is inadequate, e.g. the utilization of solar energy is low, because the band gap of TiO₂ is wide and only short UV light wavelength can be absorbed; TiO₂ can not absorb the dye due to its strong polarity, to some extent, limited the dye-sensitized solar cell efficiency. Therefore, in order to solve the above shortcomings, we take two effective measures in this thesis .TiO₂ were prepared by sol-gel method and its modified properties by dopping Zn, Sn–ion. Then we got the optimum process by orthogonal test. By means of X-ray diffraction (XRD), UV-visible spectroscopy (UV-VIS), scanning electron microscopy (SEM) and energy spectrum analysis included (EDS) ,the optimized samples were analyzed and characterized. The results reveal that : the optimal condition of Sn, Zn doped TiO₂ is Sn1.5: Zn0.5: Ti10, PH value of sol - gel solution is 3; (Sn, Zn) doped TiO₂ is feasible and effective, UV - visible absorption spectra shows that the excitation wavelength of doped TiO₂ compare TiO₂, there is 37nm red shift, and the band gap of composite TiO₂ and TiO₂ band gap were 2.93eV and 3.21eV; from the comparison of XRD between composite TiO₂ and TiO₂ ,it is obtained that (Zn, Sn) doped TiO₂ is a combination of chemistry, not the physical mixing.Secondly, for the problem of high polarity and its poor adsorption of the dye, TiO₂were prepared by sol-gel method and its modified properties by using anionic DBS, cationic CTAC, non-ionic surfactants. In order to study the modification mechanism and the effect of surface modification on morphology and optical properties, the samples were analyzed and characterized by means of infrared spectroscopy (FT-IR), X-ray diffraction (XRD), UV-visible spectroscopy (UV-VIS), scanning electron microscopy (SEM). The results show that the modification mechanism of surfactant on TiO₂ is the atom S,N,N of DBS,CTAC and PAM interaction with TiO₂ surface; compared with unmodified TiO₂, modified TiO₂ produced a red shift and the modifying effect of DBS is better than CTAC, PAM in red shift and morphology.