| Nano hematite is a type of perfect and functional material with more uniquephysical and chemical properties. When-Fe2O3particles decreased to a certain size(1~100nm), its surface atoms, ratio of surface area and surface energy increase rapidlywith the particle size decreasing. Thus nano hematite represents the characteristics ofsmall size effect, quantum size effect, surface effect and macroscopic quantum tunneleffect etc. In addition, nano hematite also has favorable optical, magnetic and catalyticproperties. It was widely applied in many fields such as color, catalysis, magnet, sensor,field mission and battery and so on.-Fe2O3, as n-type semiconductor, has narrower band (Eg=2.2eV), and betterphotoelectric response to infrared light and visible light, so it is a very promisingphotoanode material. Hematite has a rich content in the earth crust, and it has theadvantages of stable and non-toxic etc. Meanwhile, it also has some shortcomings,such as poorer conductivity, shorter distance of vavancy diffusion, easier combinationof electron-hole etc. So modifing nano hematite becomes a research in focusing toimprove its photoelectrochemical properties. Studying of preparation, morphology,structure and properties of nano hematite (as a new type of semiconductor materials)can provide ideas and basis to the other semiconductors research, and well maketheoretical guidance.In this paper, nano Fe2O3was applied in the working electrode of Dye SensizedSolar Cell (DSSC). Optimization of preparation process improves the conversionefficiency of DSSC, and provides experimental fundamental to realize the large scaleapplication of DSSC.The main research work and results in this paper are as follows:(1) Explore the condition of the best preparation process as the working electrode.-Fe2O3nanorods array films on the FTO with FeCl3.6H2O as iron source wereobtained by hydrothermal method combined with sintering method.By comparing the morphology of the samples, the temperatures and time of the hydrothermal method had certain influence on the morphology and length of hematitenanorod arrays. The nanorod arrays become more regular when the temperatureincreasing，and the nanorod lengths become longer when the time becomes longer. Sothe best process of hydrothermal method was determined: reaction temperature is110℃, reaction time is12h.(2) Study annealing process in different gases had an effect on hematite nanorodarray films. After β-FeOOH was obtained by hydrothermal method, and sintered to getthe Fe2O3nanorods array films. The samples were sintered in the four different gasessuch as Air, Ar, N2and Vacuum, and the other parameters of the annealing processwere same. That is, sintered temperature and time in the furnace is520℃for2h anda ramp rate is2℃/min. Comparison of X-ray diffraction (XRD), morphology andphotoelectrochemical properties of the samples indicated that the samples sintered indifferent gas had different characteristics of crystallization, surface morphology andphotoelectrochemical properties. The better morphology and photoelectrochemicalproperties of Fe2O3nanorod array films were found in the sintered gases of Ar and N2,and best inAr.(3) Modify the photoanodes. On the basis of getting the Fe2O3photoanode byFeCl3.6H2O as iron source, the surface of the photoanode was modified byimpregnation method combined with sintering method, by pipetting75μL aqueoussolutions of60mM Cu(NO3)2onto the hematite photoanode, and placed at the roomtemperature for3h, then sintered it in the furnace and annealed at520℃for12h aftera ramp rate of2℃/min. By analyzing the results of scanning electron microscopy(SEM), XRD and EDS (Energy Diffraction Scanning), CuFe2O4particles wereindentified around the Fe2O3nanorods and the α-Fe2O3/CuFe2O4compositephotoanode was fabricated. By comparing the photoelectrochemical propertiesbetween α-Fe2O3/CuFe2O4and pure α-Fe2O3photoanodes, the properties of theα-Fe2O3/CuFe2O4composite electrode were better than that of pure-Fe2O3electrode.(4) Assemble solar cell. Pure α-Fe2O3photoanodes and the α-Fe2O3/CuFe2O4composite photoanodes were made in different gas as working electrode, then a sulfurelectrolyte was prepared, and platinum with plating conductive glass was used as thecounter electrode and gold (Au) Quantum dots and dye N719were sensitized on thepure α-Fe2O3photoanode and the α-Fe2O3/CuFe2O4composite photoanode. DSSC wassuccessfully assembled. The voltage-photocurrent characteristics curves and externalquantum efficiencies (EQE) of the DSSCs were tested and open voltage VOC, shortcurrent JSCand fill factor FF and conversion efficiency η were determined. The resultsshowed that the conversion efficiency η of DSSC dyed in N719on α-Fe2O3/CuFe2O4composite electrode as working electrode was the highest among all the solar cell andη was3.6%. |
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