Study On The Preparation And Photoelectric Properties Of Composite Photoanodes For Dye-sensitized Solar Cells

Dye-sensitized solar cells(DSSCs)have been favored by many researchers due to their simple preparation process,low cost,abundant raw materials,and high photoelectric conversion efficiency.They have become a research hotspot in recent years and are used in the development and utilization of solar energy.It has very good application prospects.DSSCs are mainly composed of photoanode,counter electrode,electrolyte and dye sensitizer.As the core part of DSSCs,photoanode has a direct impact on the photoelectric conversion efficiency of DSSCs.According to research,it is possible to effectively improve the photoelectric performance of DSSCs by changing the structure of the photoanode and preparing the composite photoanode.The ZnO photoanode has the advantages of high carrier mobility,high chemical stability,and abundant raw materials.In this thesis,a two-dimensional ZnO nanosheet film grown on a vertical substrate was prepared by a chemical bath deposition method to explore its photoelectric properties.TiO2 is the most widely studied and the best performance DSSCs photoanode material.In order to improve the photoelectric conversion efficiency of the device,the photoanode structure is adjusted and the performance difference of the scattering layer TiO2 device is compared.Studies have shown that the ZnO composite film photoanode can effectively inhibit the occurrence of dark reactions,reduce the recombination of electrons and holes,thereby improving the conversion efficiency of DSSCs,so the ZnO/TiO2 composite photoanode structure was prepared to explore its photovoltaic performance.The specific research content mainly includes the following aspects:Firstly,different seed layers were prepared on the conductive glass by spin coating method and dipping and drawing method,and then the prepared seed layer was used as the substrate.Compare their photoelectric performance parameters.Finally,two-dimensional ZnO nanosheet films growing vertically on the substrate of the seed layer were prepared by chemical bath deposition method.The effects of seed layer type and thickness on the photoelectric properties of ZnO nanosheets were investigated.Meanwhile,ZnO nanosheets with different thickness were prepared by adjusting the growth time of chemical bath.The experimental results showed that ZnO NSS film with a thickness of about 92 nm was prepared on FTO conductive glass by dihydrate zinc acetate,ethanolamine and ethylene glycol methyl ether as raw materials.After the heat treated seed layer was immersed in 0.15 mol/L growth solution under 90℃ for 4 h,the best ZnO NSS film performance was obtained.The PCE of the prepared DSSCs is 2.95%,in which VOC is 0.64V,JSC is 11.28 mA·cm-2,and FF is 0.68.Three different photoanode materials were prepared:pure P25,pure 2-D TiO2 and P25-2D Ti02.The ultraviolet transmittance analysis showed that the substrate P25-2-D TiO2 had the highest transmittance.By comparing the adsorption capacity of the three photoanodes,it can be seen that the adsorption capacity of pure P25 dye is the highest,because there are more cracks on the surface of pure P25,and the dye penetration ability is strong.The membrane structure of the latter two films is complex,and the gap on the surface of the film is reduced,and the adsorption capacity of the dye is reduced.By comparing the photoelectric properties of the three,it can be seen that the photoelectric conversion rate of P25-2-D TiO2 is the highest,because the existence of light scattering layer makes the solar light energy more absorbed and utilized.In order to explore the effect of composite photoanode structure on the performance of DSSCs,firstly,growth solutions of different concentrations were prepared,and it was concluded that the highest photoelectric conversion efficiency of ZnO/TiO2 composite DSSCs was 2.96%when the growth solution concentration was 0.30mol.Then three different photoanode materials were prepared and compared their photoelectric properties.It was concluded that the photoelectric conversion efficiency of the ZnO/TiO2 composite structure reached 2.55%,which was 19.7%and 28.7%higher than that of the single ZnO and TiO2 photoanode structure,respectively.