DSSC染料敏化太阳能电池-英文.ppt

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1、TheorynSchematic of Graetzel CellThe adsorbed dye molecule absorbs a photon forming an excited state. dye*The excited state of the dye can be thought of as an electron-hole pair (exciton).The excited dye transfers an electron to the semiconducting TiO2 (electron injection). This separates the electr

2、on-hole pair leaving the hole on the dye. dye*+The hole is filled by an electron from an iodide ion. 2dye*+ + 3I- 2dye + I3-TheoryTheory: Charge SeparationCharge must be rapidly separated to prevent back reaction.Dye sensitized solar cell, the excited dye transfers an electron to the TiO2 and a hole

3、 to the electrolyte.In the PN junction in Si solar cell has a built-in electric field that tears apart the electron-hole pair formed when a photon is absorbed in the junction.ObjectivenLearn about the photovoltaic effect.nUnderstand the Scherrer formula.Procedure: TiO2 SuspensionBegin with 6g colloi

4、dal Degussa P25 TiO2Incrementaly add 1mL nitric or acetic acid solution (pH 3-4) nine times, while grinding in mortar and pestleAdd the 1mL addition of dilute acid solution only after previous mixing creates a uniform, lump-free pasteProcess takes about 30min and should be done in ventilated hoodLet

5、 equilibrate at room temperature for 15 minutesProcedure: Deposition of TiO2 Filmq Align two conductive glass plates, placing one upside down while the one to be coated is right side upq Tape 1 mm wide strip along edges of both platesq Tape 4-5 mm strip along top of plate to be coatedq Uniformly app

6、ly TiO2 suspension to edge of plateq 5 microliters per square centimeterq Distribute TiO2 over plate surface with stirring rodq Dry covered plate for 1 minute in covered petri dishProcedure: Deposition of TiO2 Film Anneal TiO2 film on conductive glass Tube furnace at 450 oC 30 minutes Allow conducti

7、ve glass to cool to room temperature; will take overnight Store plate for later useProcedure: Preparing Anthrocyanin Dye Natural dye obtained from green chlorophyll Red anthocyanin dye Crush 5-6 blackberries, raspberries, etc. in 2 mL deionized H2O and filter (can use paper towel and squeeze filter)

8、Procedure: Staining TiO2 Film Soak TiO2 plate for 10 minutes in anthocyanin dye Insure no white TiO2 can be seen on either side of glass, if it is, soak in dye for five more min Wash film in H2O then ethanol or isopropanol Wipe away any residue with a kimwipeProcedure: Carbon Coating the Counter Ele

9、ctrode Apply light carbon film to second SnO2 coated glass plate on conductive side Soft pencil lead, graphite rod, or exposure to candle flameProcedure: Assembling the Solar CellPlace two binder clips on longer edges to hold plates together (DO NOT clip too tight)Place 2-3 drops of iodide electroly

10、te solution at one edge of platesAlternately open and close each side of solar cell to draw electrolyte solution in and wet TiO2 filmEnsure all of stained area is contacted by electrolyteRemove excess electrolyte from exposed areasFasten alligator clips to exposed sides of solar cellProcedure: Measu

11、ring the Electrical OutputAttach the black (-) wire to the TiO2 coated glassAttach the red (+) wire to the counter electrodeMeasure open circuit voltage and short circuit current with the multimeter.For indoor measurements, can use halogen lampMake sure light enters from the TiO2 sideMeasure current

12、-voltage using a 1 kohm potentiometerThe center tap and one lead of the potentiometer are both connected to the positive side of the currentConnect one multimeter across the solar cell, and one lead of another meter to the negative side and the other lead to the loadResultsnOpen circuit voltage: 0.3

13、88 VCurrent vs. Voltage050100150200250300050100150200250300350voltage (mV)current (mA)Analysis: PowernMaximum Power: 21 mWnActive Area: 0.7 in2 Max. power per unit area: 30 mW/in2Power vs. Voltage0510152025050100150200250300350voltage (mV)power (mW)QuestionsnApproximate TiO2 particle size: assume 25

14、 nm diameternNumber of TiO2 units per nanoparticle:nVolume of one nanoparticle = 8.18 * 10-18 cm3nDensity of TiO2 4 g/cm3 Mass of one nanoparticle = 3.27 * 10-17 gnMolar mass of TiO2 = 79.87 g/mol moles of TiO2 in one nanoparticle = 4.10 * 10-19 molesn4.10 * 10-19 moles * 6.022 * 1023 molecules/mole

15、 = 2.48 * 105 TiO2 units per nanoparticlenNanoparticle surface area per gram:nNumber of nanoparticles per gram = 1/(3.27 * 10-17) = 3.06 * 1016 nanoparticlesnSurface area of one nanoparticle = 1.96 * 10-15 m2nSurface area per gram = 3.06 * 1016 nanoparticles/gram * 1.96 * 10-15 m2/nanoparticle = 60.

16、0 m2/gramQuestionsnFraction of atoms that reside on the surface:nSurface area of one particle = 1.96 * 10-11 cm2nApproximate atoms per unit area = 1015 atoms/cm2nAtoms on surface = 1.96 * 10-11 cm2 * 1015 atoms/cm2 = 1.96 * 104 atomsnFraction of atoms on surface = (1.96 * 104)/(2.48 * 105) = 0.079nWay to improve experiment:nFilter raspberry juice using a better filter system