Preparation Of ZnO Composite Photoanode Film And Study On The Photoelectric Performance Of Dye-Sensitized Soalr Cells

ZnO photoanode,an important component of dye-sensitized solar cells?DSSCs?,acts as a carrier for dye and is responsible for transferring electrons to external circuit.The purpose of this paper was to prepare ZnO photoanodes with huge specific surface area,higher dye adsorption amounts,super electronic transmission performance and DSSCs with higher photoelectric conversion efficiency?PCE?.In this paper,the main studies were as follows:at a certain condition,chemical bath deposition method and polyol-mediated thermal refluxing method were separately applied to prepare upright-standing ZnO nanosheets film and Li⁺-doped ZnO nanoaggregates structure.ZnO composite photoanode film was fabricated by combining the two ZnO structures.X-Ray Diffraction and Scanning Electron Microscope were used to characterize the structure and morphology of ZnO.Electrochemical Impedance Spectroscopy was also carried out to analyze the internal electronic transmission performance.J-V curves of DSSCs were tested.The main content and results were as follows:?1?Various seed layers were prepared on the FTO substrates using spin-coating method and dip-coating method.Then upright-standing ZnO nanosheets were fabricated on the seed layer by chemical-bath deposition method.The effects of the varieties and thickness of seed layers on the photoelectric performance of ZnO DSSCs were studied.When chemical bath temperature is 90oC,the reaction time is 4 h,zinc nitrate concentrations is 0.15 mol/L,the corresponding ZnO nanosheets based DSSCs possess the optimum performance,with corresponding seed layer were prepared by dipping the FTO into ethylene glycol methyl ether solution consisting of 0.3 mol/L zinc acetate dihydrate and 0.3 mol/L diethanolamine only one time.The best performance parameters were as follows:J_sc=11.81 mA·cm^-2,V_oc=0.62 V,FF=0.68,PCE=4.98%,respectively.?2?ZnO nanoaggregates were prepared by hydrolyzing and condensing zinc acetate dihydrate in diethylene glycol under reflux for 8 h.ZnO nanoaggregates,as light scattering layer,were covered on ZnO Nanosheets film by employing spin-coating method,dipping coating method and doctor-blade method,respectively.The effects of ZnO nanoaggregates layers fabricated by different processes on the photoelectric properties of ZnO DSSCs were studied.The results indicated that:the internal impedance would be too large for ZnO DSSCs when the light scattering layers were with excessive thickness,thus PCE could not be improved.The light scattering layer synthesized by dipping ZnO Nanosheets in ZnO nanoaggregates solution for 2 min was favored of improving the photoelectric properties of ZnO DSSCs.Finally,corresponding perfermance parameters were listed below:J_sc=15.05mA·cm^-2,V_oc=0.68 V,FF=0.60,PCE=6.13%,respectively.?3?ZnO nanoaggregates-nanosheets composite film was prepared via hydrothermal method,with suspending the ZnO nanoaggregates film upside-down in a sealed bottle containing an aqueous solution of zinc nitrate with a certain concentration and 16.7wt%of urea at 90oC for different reaction time to form layered hydroxide zinc carbonate,which further transforms into ZnO nanosheets in the following annealing step.It turned out that:ZnO composite film prepared in 0.07mol/L growth solution at 90oC for 4 h showed the best photoelectric performance.Corresponding perfermance parameters were as follows:J_sc=17.02 mA·cm^-2,V_oc=0.60 V,FF=0.60,PCE=6.06%.We were surprised to find out that ZnO nanoaggregates-nanosheets composite film could also synthesized by chemical-bath deposition in 0.15 mol/L growth solution for 2 h,with PEO based electrolyte introduced,DSSC achieved PCE of 5.60%.