Fabrication And Photovolatic Performance Of The Photoanode In Dye-sensitized Solar Cells With ZnO Nanomaterials

The energy crisis and environmental pollution has become increasinglyprominent, imminent and urgent to be resolved. The exploitation and utilization ofsolar energy, combined with the realizing of the sustainable development of energy,has been a key to alleviate the energy crisis and environmental pollution situation.Solar cells as one effective devices of solar photovoltaic application, have attractedmore and more scientists to study it. In this dissertation, the current situation ofresearch and development for solar cells were summarized in detail, especially thecomponents, working principle, impact factor of the optical properties, andcharacterization testing methods of dye-sensitized solar cells（DSSCs）. Thedissertation focus on the improvement of photo-to-electron conversion efficiency forZnO DSSCs, and the main contents are listed as follows:1. The ZnO nanocrystalline photoanodes were treated by Zinc acetate aqueoussolution. The influence of surface chemical modification processing and processingtime on photovolatic performance and electrochemical properties in ZnOnanocrystalline DSSCs was discussed. It is shown that some nanoaggregates wereformed in ZnO nanocrystalline photoanodes after surface chemical modificationprocessing, and the number of nanoaggregates increase with the increased processingtime. In addition, the size distribution of nanoaggregates was more wider, whichsurface was filled with micropores. On the one hand, the nanoaggregate can reducethe number of grain boundary between nanocrystalline particles, thus reducing theelectron scattering and recombination rate of the photoinjected electrons. On the otherhand, the nanoaggregate can act as light scattering to increase the harvesting of solarlight. The micropores of the surface are conducive to the infiltration of the electrolytesolution.2. The hollow TiO₂nanofibers were prepared by coaxial electrospinning. Thenovel TiO₂nanofiber/ZnO nanoparticle composite photoanodes were prepared bydispersing TiO₂nanofibers with a series of different mass ratios intopolyethyleneglycol （PEG2000）, followed by adding ZnO nanoparticle paste, then thecomposite paste was sonicated by ultrasonic cleaner for realization the uniformdistribution of the nanofibers. The reseach of light harvest for composite photoanodes,among which TiO₂nanofibers act as light scattering, and the photoelectric conversion efficiency of DSSCs with different mass fraction of TiO₂hollow nanofibers werecarried out. Meanwhile, the reseach with respect to the effect of energy barrier formedducing to the difference of energy level for ZnO and TiO₂was carried out too. It isshown that the light harvesting of composite photoanode is gradually increased withthe incorporation of the TiO₂hollow fibers, especially with wavelengths in the regionof600～800nm. The maximum short circuit current density of13.15mA cm-2combined with the highest photoelectric conversion efficiency of4.59%was obtainedwhen the mass fraction of TiO₂hollow fibers was10%.3. ZnO nanosphere was prepared by electrospraying combined with sol-gelprocess, and the DSSCs used ZnO nanosphere as electrode raw materials werefabricated. Photovoltic performance was measured, and the electron recombinationbetween photoanode and eletrolyte were discussed by utilizing electrochemicalimpedance spectroscopy （EIS） under dark. It is shown that the photoanode made ofZnO nanosphere can effectively suppress electron recombination, because of whichthe electrons have a long electronic life.