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1、Dye Sensitized Nanocrystalline Photovoltaic Cell,Group 1 Luke,Matt,and Jeff,Theory,Schematic of Graetzel Cell,The 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 electro
2、n to the semiconducting TiO2(electron injection).This separates the electron-hole pair leaving the hole on the dye.dye*+The hole is filled by an electron from an iodide ion.2dye*+3I-2dye+I3-,Theory,Theory:Charge Separation,Charge must be rapidly separated to prevent back reaction.Dye sensitized sola
3、r cell,the excited dye transfers an electron to the TiO2 and a hole 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.,Objective,Learn about the photovoltaic effect.Understand
4、the Scherrer formula.,Procedure:TiO2 Suspension,Begin with 6g colloidal 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 pastePr
5、ocess takes about 30min and should be done in ventilated hoodLet equilibrate at room temperature for 15 minutes,Procedure:Deposition of TiO2 Film,Align two conductive glass plates,placing one upside down while the one to be coated is right side upTape 1 mm wide strip along edges of both platesTape 4
6、-5 mm strip along top of plate to be coatedUniformly apply TiO2 suspension to edge of plate5 microliters per square centimeterDistribute TiO2 over plate surface with stirring rodDry covered plate for 1 minute in covered petri dish,Procedure:Deposition of TiO2 Film,Anneal TiO2 film on conductive glas
7、sTube furnace at 450 oC30 minutesAllow conductive glass to cool to room temperature;will take overnightStore plate for later use,Procedure:Preparing Anthrocyanin Dye,Natural dye obtained from green chlorophyllRed anthocyanin dyeCrush 5-6 blackberries,raspberries,etc.in 2 mL deionized H2O and filter(
8、can use paper towel and squeeze filter),Procedure:Staining TiO2 Film,Soak TiO2 plate for 10 minutes in anthocyanin dyeInsure no white TiO2 can be seen on either side of glass,if it is,soak in dye for five more minWash film in H2O then ethanol or isopropanolWipe away any residue with a kimwipe,Proced
9、ure:Carbon Coating the Counter Electrode,Apply light carbon film to second SnO2 coated glass plate on conductive sideSoft pencil lead,graphite rod,or exposure to candle flame,Procedure:Assembling the Solar Cell,Place two binder clips on longer edges to hold plates together(DO NOT clip too tight)Plac
10、e 2-3 drops of iodide electrolyte 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 side
11、s of solar cell,Procedure:Measuring the Electrical Output,Attach 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 t
12、he TiO2 sideMeasure current-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 load,Result
13、s,Open circuit voltage:0.388 V,Analysis:Power,Maximum Power:21 mWActive Area:0.7 in2 Max.power per unit area:30 mW/in2,Questions,Approximate TiO2 particle size:assume 25 nm diameterNumber of TiO2 units per nanoparticle:Volume of one nanoparticle=8.18*10-18 cm3Density of TiO2 4 g/cm3 Mass of one nano
14、particle=3.27*10-17 gMolar mass of TiO2=79.87 g/mol moles of TiO2 in one nanoparticle=4.10*10-19 moles4.10*10-19 moles*6.022*1023 molecules/mole=2.48*105 TiO2 units per nanoparticleNanoparticle surface area per gram:Number of nanoparticles per gram=1/(3.27*10-17)=3.06*1016 nanoparticlesSurface area
15、of one nanoparticle=1.96*10-15 m2Surface area per gram=3.06*1016 nanoparticles/gram*1.96*10-15 m2/nanoparticle=60.0 m2/gram,Questions,Fraction of atoms that reside on the surface:Surface area of one particle=1.96*10-11 cm2Approximate atoms per unit area=1015 atoms/cm2Atoms on surface=1.96*10-11 cm2*1015 atoms/cm2=1.96*104 atomsFraction of atoms on surface=(1.96*104)/(2.48*105)=0.079Way to improve experiment:Filter raspberry juice using a better filter system,
