| Dye-sensitized solar cell (DSSC). photoelectrochemical device consisting of a dye-sensitized anode, a redox electrolyte, and a counter electrode, has attracted grow ing interests because of its merits on low-cost, relatively high power conversion efficiency, easy fabrication, and environmentally friendly. The photoanode of DSSC can be seen as a’vehicle’to transport the electrons injected from the excited dye molecule to an external circuit. Therefore, it can significantly affect photocurrent and photovoltage of the cells. The current DSSCs always suffer from incomplete dye excitation, recombination of photogenerated electrons with electrolyte and dye degradation, giving unreasonable open-circuit voltage (Voc) and short-circuit current density (Jsc). Therefore, a prerequisite in elevatingpower conversion efficiency of DSSCs is to enhance their Voc and Jsc.In the second and third chapters, we demonstrate the critical issue of elevating dye excitation, suppressing electron-iodide recombination, and increasing dye stability is transmission enhancement of photoanode synthesized by incorporating electron-insulating SiO2 with TiO2 via a hydrothermal process. However, the unfavorable power conversion efficiency is still a tremendous obstacle for this promising SiO2/TiO2 composite photoanode in highly efficient DSSCs. Aiming at significantly improving electron density collected on CB of TiO2 and therefore enhancing power conversion efficiency, our approach exploits employment of SiO2 during hydrothermal process, leading to an increased transmission of photoandde, decreased recombination reaction of electrons as well as improved dye loading and photostability. Through experiments, we have demonstrated that the incorporation of TiO2 by SiO2 is an effective strategy for enhancing dye excitation, suppressing backward recombination reaction of electrons and electrolyte, and increasing dye photostability. From transmittance test, we found that accession of SiO2 can make the light reaching the surface of TiO2 produce interference effects in order to enhance light intensity and improve excite the dye. From UV-vis diffuse reflection spectra, we found that the Eg is increased by incorporating SiO2 into TiO2 in comparison with that of pure TiO2 to decrease the photocatalytic ability of TiO2. From Raman and FTIR spectra, we found that detection of Si-O-Ti bond may be used to support the hypothesis that the amorphous SiO2 nanoparticles have been dissolved and reorganized in the hydrothermal process. Further proof. TiO2 doped by SiO2 can create more active sites for adsorption of the dye. From SEM and TEM. the functions of SiO2 can be concluded as follows:(ⅰ) elevating transmission of SiO: incorporated TiO2 crystallite photoanode, giving increased dye-excitation efficiency and electron injection; (ⅱ) covering TiO2 surface, blocking partial recombination reaction of electrons with electrolyte; (ⅲ) doping TiO2 lattices, creating more active sites for dye adsorption. Incorporation of SiO2 with TiO2 is expected to give a block of electrons from electrolyte. And because of the added SiO2, recombination of electrons and electrolyte has been hindered obviously. The DSSC from 1 wt% SiO2 incorporated TiO; nanocrystallite provides an impressive power conversion efficiency of 9.98% in comparison with that of 6.13% from pure TiO; photoanode. At the same time, Using TiO2/SiO2-(ⅱ) the method efficiency composite anode obtained light has also been greatly improved. The DSSC from TiO2/SiO2-(ⅱ) method provides a higher power conversion efficiency of 9.83% than 7.06% from pure TiO2 based DSSC.In the fourth chapter, chemical method is applied to synthesize the conductive PANi electrode doped by hydrochloric acid, sulfuric acid and phosphoric acid, respectively. And the properties of the prepared PANi electrodes are characterized by UV-visible spectroscopy, infrared spectroscopy, Raman Spectroscopy, XRD, SEM cyclic, voltammetry, impedance spectra and Tafel curves. The SEM test showed that; the PANi electrodes are nanostructures and evenly distributed on the conductive surface of the glass. Three pairs of redox peaks are well distinguished in the cyclic voltammograms for all the three electrodes, among which sulfuric acid doped polyaniline electrode is the strongest and has an excellent electrochemical catalytic performance. The impedance spectra and Tafel curves showed that, the polyaniline electrode prepared by chemical methods obtain a lower resistance and an excellent performance. Meanwhile, the outstanding performance of the PANi doped by sulfuric acid is verified by the UV-vis. IR. Raman Spectroscopy and XRD. Photovoltaic properties is characterized by assemble the polyaniline electrode and dye-sensitized titanium dioxide photo-anod.After only about twenty years. DSSC research has made great progress in all aspects of dyes, electrodes and electrolytes. At the same time, there are a lot of room for development in high efficiency, stability, durability and so on. This new type of solar cell has a broader purpose than silicon cells:plastic or metal sheets are available to make it lightweight and thin film; a variety of colorful dyes are available to make it colorful; in addition, it can also be designed into a variety of shapes solar cells to make it diversify. In short. DSSC has a very broad industrial prospects. And it is a fairly new type of solar cell which has a broad prospec.1 believe that in the near future. DSSC will come into our lives. |
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