Effect Of Polymer Dye Sensitizers And Photoanode Modification On The Photovoltaic Performance Of Dssc

Dye sensitized solar cells (DSSCs) have attracted considerable attention because of their low-cost materials, easy of fabrication and photoelectric conversion efficiency not-affected by temperature compared with silicon-based photovoltaic devices. The energy conversion efficiency of DSSC as high as12.3%has been achieved under AM1.5simulated solar light, which will be a new generation alternative of applicable and high efficiency solar cells instead of silicon solar cells. Dye sensitizers and the nanoporous semiconductor thin film are important components of the DSSCs. In the dissertation the effects of polymer dye sensitizers and photoanode modification on the photovoltaic performace of DSSC were detailed studied respectively.5,8-dithiophene quinoxaline (A1Q1A1),5,7-dithiophene thienopyrazine (A1Q2A1) and4,7-dithiophene benzothiazole sulfide(DTBT) were selected as the electrochemical polymerization monomers. Three electrodes method was conducted to prepare the polymer dyes by making the above monomers being homopolymerized, copolymerized and block polymerized into the electrolyte Solution of tetrabutylammonium hexafluorophosphate. The polymers dye sensitizers were characterized by IR, UV-Vis and DSC. The effects of polymerization methods, polymerization time and doping/dedoping electrolyte on the device performances were discussed. The result shows that A1Q1A1-B-A1Q2A1block polymer sensitizer has the best device performances of η=0.066%.After electrolyte dedoping, the device performance was enhanced by2-3times.The ZnO layer was fabricated by hydrothermal, paste and dip-coating methods, respectively, and subsequent TiO2/ZnO composite photoanodes were prepared. CdS quantum dots were synthesized by chemical bath deposition and the influence of co-sensitization of CdS quantum dots and N719dye on device performance were discussed. According to the analysis of UV-Vis spectrum and electrochemical impedance spectroscopy of CdS/N719co-sensitizated device, the photoresponse range was broader and the lifetime of electron was longer after co-sensitization of CdS quantum dots and N719dye. The best device efficiency of3.14%was achieved using TiO2/ZnO composites photoanode fabricated by dip-coating method and sensitized only by N719dye. The different layers of TiO2and the absorbing capacity of CdS quantum dots also affect the device performance. The optimized device efficiency was enhanced to3.36%after co-sensitization of CdS quantum dots and N719dye.Finally, the photoanode was modified by dip-coating acetate and chloride respectively. A new oxide film surface was formed after photoanode modification characterized by XPS and XRD measurement. According to the UV-Vis spectrum and electrochemical impedance spectroscopy, the photoresponse range was broader and the lifetime of electron was longer because of the formation of new oxide film. The dark reaction of internal device was also suppressed. When the photoanode was dipped into acetate solution, the device efficiency of solution concentration0.005mol/L was better than0.05mol/L one. Effects of different dip-coating time and materials on affected the device performance were also discussed. The efficiency of5.38%and5.41%were obtained by dip-coating magnesium acetate and zinc chloride,.respectively.