Preparation Of Dye-Sensitized Solar Sells Based On ZnO Thin Films And Study Of Their Photovolatic Performance

Energy crisis has been a worldwide problem of human beings facing with the rapid develpoment of science and technoloy. With the exhaustion of fossil fuels and environmental pollution caused by the combustion of fossil fuels, it is a serious threat to survival and development of human beings. Under these circumstances, photovolatic solar cells have attracted lots of research attentions. Dye-sensitized solar cells (DSSCs) have been an active research project since 1991 because of simple preparation technology, low cost, nontoxic and pollution-free. Well-oriented ZnO nanorod arrays (NRs) thin film is an ideal photoanode material, due to the abundant source, large suface area, high energy conversion efficiency. ZnO NRs thin films have been a hotspot in the area of new energy materials and devices.In this study, ZnO NRs thin films with high orientation along c-axis were prepared by the hydrothermal method and electrochemical method. We investigated the crystal structure, and surface morphology of ZnO films. ZnO NRs electrodes sensitized by N719 dye, CdS quantum dots (QDs) were sucessfully prepared and we also investigated their photoelectrochemistry properties. The results of this work are summarized as follow:(1)We synthesized ZnO NRs thin films with the hydrothermal and electrochemical deposition methods. We discussed the process parameters influence to the ZnO nanorods’growth. The results showed that ZnO NRs thin films with good crystallization and preferred orientation, regular shape and orthohexagonal tip are obtained by two methods. However, vertically well-aligned ZnO nanorod arrays with greater aspect ratio and higher orientation growth along c-axis were synthesized by hydrothermal method.(2)The ZnO film electrodes sensitized with CdS QDs via successive ion layer adsorption method were sucessfully prepared as the photoanode of DSSCs. The morpology, crystal structure and optical properties of ZnO/CdS double layer thin films electrodes were studied by X-ray diffraction (XRD), Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and UV-visible spectrophotometer (UV-vis) experiments. We also investigated the effect of differernt CdS deposition cycle times, the morphology of ZnO thin films and the different co-sensitization time by the solar cells testing system. The results showed that the CdS QDs with the cubic structure have completely covered on the surface of ZnO thin films. Moreover, The amount of CdS QDs can be controlled by changing the deposition times. The experiment results demonstrated that the spectrum response system of ZnO thin film electodes extended from the ultravilet region to the visible region. The results demonstrated that the power conversion efficiency of ZnO/CdS solar cells is enhanced with the increasing of CdS QDs amount on the surface of ZnO thin films and reached the maxium when depostion times arrives at 9 or 10. The photovolatic performance enhancement is mainly due to the stronger light harvesting, the reduction of electron-hole recombination and the enhancement of electron transfer and transmission with the introduction of CdS QDs. At the same time, when the co-sensitizition time between CdS QDs and N719 dye is up to 18h, DSSCs can obtain higher energy conversion efficiency and quantum efficiency.(3)ZnO nanorods powder was synthesized via a simple hydrothermal method and ZnO thin films were prepared by paste coating in th paper. Then the ZnO NRs thin films co-sensitized by CdS QDs and N719 dye were used as photoanode in DSSCs. We discussed the impact of the morphology of ZnO thin films prepared by three methods on the photoelectric properties. The result showed that the solar cell based on ZnO NRs thin films prepared by hydrothermal method obtained excellent photovolatic performance.