Preparatiom And Properties Of Light Anode For Dye-Sensitized Solar Cells

Dye-sensitized solar cells have great development potential because of its high photoelectric conversion efficiency, easy preparation and low cost. This paper prepared a light anode of dye-sensitized solar cells, including preparation of nano-titanium dioxide thin films, spectral properties of rhodamine B, fluorescein and asymmetric squaraine indocyanine dye, and sensitization of nano-TiO₂ thin films.Nano-TiO₂ thin films were prepared on ITO conductive glass by sol-gel method from tetrabutyl titanate (TBT) as precursor, ethanol as solvent, diethanolamine as chelating agent and polyethylene glycols (PEG) as surfactant at room temperature in this paper. XRD confirmed that crystal form of the nano-TiO₂ thin films was anatase; the results of step profiler measurement showed that the film thickness was about 68⁷5 nm. Besides, the field emission scanning electron microscope proved that diameter of the nano-TiO₂ particles was 30⁵0 nm, the holes on the film surface distributed evenly and the pore size was 200³00 nm, and holes area could reach 80%.The maximum UV-Vis absorption wavelength of rhodamine B, fluorescein and asymmetric squaraine indocyanine dye were 544 nm, 485 nm and 630 nm in methanol, respectively, and absorption intensity of them increased with increase of their concentrations; molecules of fluorescein could aggregated to lead absorption intensity increased at 441 nm when fluorescein concentration was greater than 5.0×10^-4 mol/L; in ethanol aqous solution with cyclodextrin or rare earth ions, there was no significant change in the spectrum of rhodamine B or fluorescein, but the fluorescence emission intensity of the asymmetric squaraine indocyanine dye enhanced with cyclodextrin. When any two of the dyes mixed in methanol solution, fluorescein made UV-Vis absorption intensity of asymmetric squaraine indocyanine dyes decreased slightly and absorption wavelength of rhodamine B red shifted; asymmetric squaraine indocyanine dye could restrain the aggregation of fluorescein, reduced absorption intensity of fluorescein at 441 nm and enhanced absorption intensity at 485 nm. The solution of rhodamine B, fluorescein and asymmetric squaraine indocyanine dye had good absorption intensity between 200 nm and 660 nm.The nano-TiO₂ thin films were sensitized with the dyes by impregnation method and new sensitizing method, respectively. The mixture of asymmetric squaraine indocyanine dye and fluorescein in methanol became the best sensitizer for the films. Open circuit voltage of the dye-sensitized solar cell with the film anode could reach 280 mV, and short-circuit current was 0.498 mA. The two methods could make the dye have good effect for sensitizing the films. Compared with the impregnation, the new sensitizing method had many advantages: the high efficiency of sensitization, dye savings, and environmentally friendly.