Dye-sensitized Solar Cell Anode Of The Light-scattering Light To Optimize And Enhance Photovoltaic Performance

Dye-sensitized solar cell （DSSC） has quickly attracted keen interest of manyresearchers in the field of solar cells. This is because its structure is much differentfrom the traditional silicon-based solar cells and its low manufacturing cost, simplemanufacturing process. The vital component of the dye-sensitized solar cell structurefrom top to bottom is the photoanode, an electrolyte and electrodes respectively.Photoanode of dye-sensitized cells was made of TiO₂nanocrystalline films. In recentyears, many researchers optimized the morphology of the nanocrystalline films inorder to improve the performance of dye-sensitized cells. At the same time someresearchers invented new techniques to improve the performance of dye-sensitizedsolar cells, that is light scattering particles were embedded in the transport layerwhich was made up from the particle size of25nm TiO₂nanocrystalline films at thebottom.This thesis presents the two core-shell structures of the light scattering particles,as well as methods for their preparation, respectively, embedded in the particlediameter of25nm nanocrystalline TiO₂film at the bottom of the transport layer, asthe light scattering layer. The first one is a light-scattering particles made by theclassic Stober method and it produced uniformly dispersed SiO₂particles, let it drythen collected in solution hydrolysis of tetrabutyl titanate （TBOT） after annealing theSiO₂surface of the particles were coated anatase phase TiO₂shell, thus prepared SiO₂for TiO₂as the shell of the core-shell structure of light scattering particles; Thesecond one is in preparation complete monodispersed phosphors and the coatingmethod was similar to the above hydrolysis of tetrabutyl titanate （TBOT） outside thephosphor coated a TiO₂shell. These two light-scattering particles on theirmorphology or nature were detected and proved through a variety ofcharacterization techniques （TEM, SEM, XRD） studies; concrete steps and conclusionsare as follows:（1） Using tetraethylorthosilicate （TEOS） as the precursor solution, the hydrolysisin a mixed solution of ammonia, ethanol and water under the normal room temperature, after centrifugal and sedimentation, generally with the rotational speedof8000rpm, subsequently dried at100℃monodispersed SiO₂submicron particles,the diameter of the particles can be controlled by adjusting the ratio of the ammoniaand water. After preparing and the dry powder tested by emission scanning electronmicroscope （FESEM） display the images of monodispersed SiO₂microspheres,smooth surface without deformation and a more uniform size, according to theexperiment, the particle diameter size is generally from180nm to350nm.（2） The prepared SiO₂microspheres’ surface were coating a layer of amorphousTiO₂shell by hydrolysis of tetrabutyl titanate （TBOT）, after a variable temperatureannealing the surface coated with a layer of SiO₂particle sharp TiO₂anatasecrystalline phase shell there are two advantages to the light scattering particles.Thefirst advantage is TiO₂is a stable semiconductor material, and its oxygen adsorptioncapacity is very strong and has a high photocatalytic performance;The secondadvantage is as we known the refractive index of SiO₂is1.46, while the refractiveindex of TiO₂was2.56, according to the Mie scattering effects, when there is a largedifference of the refraction index of the internal and external materials, thecomposite particles have a high scattering effect. Therefore, the composite particlesare added into the dye-sensitized solar cells’ photoanode were feasible. After testing,assembled by the the composite particles of the dye-sensitized solar photoelectricconversion efficiency reached5.1%.（3） By the same method as described above, after the hydrolysis of tetrabutyltitanate prepared YVO₄:Eu³⁺,Bi³⁺surface-coated layer of amorphous TiO₂housing.Then through the same variable temperature annealing, form a shell of an anatasecrystalline phase of TiO₂in the surface. After tests showed that the composite lightscattering particles outside the visible band still respond to absorption of otherwavelength, in addition to a higher light scattering effect, also has a wide spectralresponse area. After testing, the photoelectric conversion efficiency of thedye-sensitized solar cell was5.6%which was assembled by the composite particles.（4） To the above-mentioned two kinds of composite particles as the lightscattering particles of the dye-sensitized solar cell, the photoelectric conversion efficiency was5.1%and5.6%, its photoelectric conversion efficiency is much higherthan the dye-sensitized solar cell without adding light scattering particles（photoelectric conversion efficiency was only3.5%）, experiments also demonstratedthe thickness of the film of the photoanode about18um was most favorable to theadsorption of the dye and the transmission of light generated carriers. Thus thedye-sensitized solar cells could obtain a higher photoelectric conversion efficiency.