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By means of first-principles calculations based on the ab initio pseudopotential and plane wave basis, we present self-consistent molecular dynamic calculations to determine a clean TiO2 crystal (001) surface geometry and surface electronic states structure. All calculations were performed for both rutile and anatase phases. Using a total energy minimization strategy, we acquired the general inward relaxations. The s-like surface states just above the lower valence band at (001) surfaces both in the rutile and anatase phases are found. The band bending effect occurs both in rutile and anatase (001) surfaces. It reduces the band gap by ac. 0.4 eV in rutile and ac. 0.8 eV in anatase, elevating the Fermi energy levels. Besides the band bending of the valence band, surface states also lie near the bottom of the conduction band. The lower surface energy of anatase makes nanocrystalline TiO2 is often in the anatase phase below a critical size.Our results are in good agreement with the previous work and experimental data. 相似文献
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The dye-sensitized TiO2 complex films were prepared by the dye coat onto TiO2 surfaces,and the sensitizing mechanism and adsorption properties of the dye-sensitized TiO2 complex films were inverstigated.The influence of the application conditions of dye adsorbed on TiO2 films on the amount of dye adsorption was discussed.Experimental results show that the concentration,the temperature of dye solutions and the dipping time of TiO2 films in the dye solutions have a significant influence on the amount of dye adsorption.Cell test indicates that the conversion efficiency of light to electricity increases with the amount of dye adsorption. 相似文献
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In order to improve the performance of the dye-sensitized solar cells based on ZnO films, ZnO nanoparticles of different sizes were prepared by two methods. Some surfactants were added into the particles to form three types of ZnO pastes. Electrodes of various thickness applied to dye-sensitized solar cell were prepared starting from each of those pastes by the screen-printing method. The performance of dye-sensitized solar cells was optimized via both the selected particle size and film thickness. The reason of the inefficiency was explained by the infrared and ultraviolet- visible absorption spectra. 相似文献
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Bipyridyl ruthenium dye N3 and N719 was synthesized, purified by the gel chromatogram method and characterized by the proton NMR and UV-Vis spectra. After the purification most of the impurities that decreased the photoelectrochemical properties were removed and the open-circuit voltage (Voc), short-circuit photocurrent density (Jsc) and overall photo-electric conversion efficiency (η) of the dye-sensitized solar cells (DSCs) increased dramatically. The standard curve of absorbance vs. concentration of N3 and N719 dye was achieved by using UV-Vis quantitative analytic spectrophotometry. This method was employed to determine the concentration of the dye solution after coating of TiO2 films. The linear concentration range of absorbance vs. concentration of N719 was between 6.25×10^-6 mol·L^-1 and 1×10^-4 mol·L^-1 with the molar extinction coefficient (ε) 1.58 ×10^4 L mol·L^-1·cm^-1 at a wavelength of 533 - 531 nm and 1.50 × 10^4 Lmol·L^-1·cm^-1 at a wavelength of 393 - 384 nm , accordingly. The linear concentration range of the N3 dye was 6.25 × 10^-6mol·L^-1 to 1.5× 10^-4 mol·L^-1 with ε of 1.47 × 10^4 L mol·L^-1· cm^-1 at a wavelength of 538 - 535 nm and 1.48 × 10^4 L ·mol·L^-1·cm^-1 at a wavelength of 399 - 393 nm. 相似文献
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