The Research Of Ultra-thin Film Quantum Dot Solar Cell Based On TiO₂-nanowires

According to the light anode materials, the development of solar cells experienced from single crystal silicon, polysilicon to compound thin films, polymer thin films and nano crystalline solar cells, this paper mainly studies in nanocrystalline solar cell. This type of battery has become a new generation of solar cell,because of its high photoelectric conversion efficiency, lower production costs, stable performance and environmental friendly characteristics.To optimization and improvement the photoanode and sensitizer are the breakthrough points for improving the photoelectric conversion efficiency of solar cells. This article mainly aims at the study of Nanocrystalline TiO₂, our research focus on how to effectively control the TiO₂ morphology for electronic to direct transmission channel and reduce electronic composite, and to increase the electron lifetime. At the same time, the N719 sensitizer is currently the most commonly used dye sensitizer. However, because of its expensive price, vulnerability to environmental interference and poor stability, all of the shortcomings result in limitation to implement sensitizer into industrial production. The semiconductor quantum dots（QDs）, due to its adjustable band gap, high extinction coefficient, multiple exciton effect, prominent photoelectric properties, has become the ideal matter instead of dye sensitizer. At the same time, it is easy to make and cost low, also the stability is good, therefore, it has great prospects to instead of the dye sensitizer.In this paper, a variety of TiO₂ nanowire materials with different morphologies were synthesized,with the method of X-ray diffraction, field emission scanning electron microscopy and high-resolution transmission electron microscopy to characterized the samples. And also the test of photoelectric conversion efficiency, charge transfer mechanisms to test compared with the several morphology. At the same time, to solve the problem of controling the size of the quantum dots and the poor diverse property and also low assembly QDSSCs efficiency, the（PA-SILAR） layer by layer self assembly method will be mentioned, and with Cd Sex S（1-x）/Cd S co-sensitized by quantum dot sensitized solar cell. The photoelectric property is to measure the photoelectric efficiency of the battery by electrochemical workstation and monochromatic light photoelectric conversion efficiency of the system. The main research content and structure are as follows:（1）The anodic film of TiO₂ mesoporous and 3D-TiO₂ nanowires, 3D-TiO₂ nanotrees were prepared by hydrothermal method.The three morphologies of different TiO₂ nanocrystal characterized respectively. And through the method of anodic oxidation to strip the anodic films, and then transfer to the FTO glass which contains barrier layer by the spinning, the will of the prepared photoanodes, and platinum electrode for assembling preparation of DSSCs, and photoelectric performance test, obtained TiO₂ nanotrees are assembled DSSCs which has the highest conversion efficiency up to 8.7%, and the short-circuit current up to 15.94（m A/cm2）. This nanotree structure not only has the advantages of one-dimensional nanostructures, but also overcome the disadvantage of specific surface area, therefore, the research has significant impact on improving the efficiency of new structure of sensitized solar cell（DSSCs）.（2）In order to have a better control of quantum dot particles size, we use the smooth TiO₂ nanowire arrays to be a substrate, by the method of polymer supported ion exchange method（ PA-LBLAR） to synthesis of Cd S quantum dots we use polyethylene imide（PEI） as a binding agent, this approach compared with the traditional ion exchange method（SILAR） can make more effectively to control quantum dot size, hence to achieve the effective control of quantum dot by controlling the deposition times. Also PA-SILAR is easier to make quantum dots dispersed, and more stablity adsorbed on the photo-anode. The PA-SILAR method can obtain higher photoelectric conversion efficiency up to 2.94%, and short-circuit current density up to 8.65 m A. cm-2.（3） In order to solve the problems of low conversion efficiency of QDSSCs, the photoelectric conversion efficiency is improved by improving the optical andode structure and quantum dot sensitized absorption band. First of all, the photo-anode is the hierarchical structure of TiO₂ nanotrees / nano-ballflower, which contains on the basis of nanotrees, outside prepared by the nano-ballflower, this structure, not only make the specific surface area increased and improve the light scattering ability, but also have the advantages of one-dimensional structure. Meanwhile, the sensitizer which by single Cd S has changed to Cd Sex S（1-x）/Cd S. The prepared TiO₂ /Cdx S（1-x）/Cd S sensitized QDSSCs has been greatly improved compared with the single Cd S sensitization, The photoelectric conversion efficiency can attain 4.79% and the short-circuit current can reached 18.01 m A.cm-2.