Dye Sensitized Nanocrystalline Photovoltaic Cell - PowerPoint PPT Presentation

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Dye Sensitized Nanocrystalline Photovoltaic Cell

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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. – PowerPoint PPT presentation

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Title: Dye Sensitized Nanocrystalline Photovoltaic Cell


1
Dye Sensitized Nanocrystalline Photovoltaic Cell
  • Group 1 Luke, Matt, and Jeff

2
Theory
  • Schematic of Graetzel Cell

3
Theory
  • 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 electron 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-

4
Theory Charge Separation
  • Charge must be rapidly separated to prevent back
    reaction.
  • Dye sensitized solar 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.

5
Objective
  • Learn about the photovoltaic effect.
  • Understand the Scherrer formula.

6
Procedure TiO2 Suspension
  • Begin with 6g colloidal Degussa P25 TiO2
  • Incrementaly add 1mL nitric or acetic acid
    solution (pH 3-4) nine times, while grinding in
    mortar and pestle
  • Add the 1mL addition of dilute acid solution only
    after previous mixing creates a uniform,
    lump-free paste
  • Process takes about 30min and should be done in
    ventilated hood
  • Let equilibrate at room temperature for 15
    minutes

7
Procedure Deposition of TiO2 Film
  • Align two conductive glass plates, placing one
    upside down while the one to be coated is right
    side up
  • Tape 1 mm wide strip along edges of both plates
  • Tape 4-5 mm strip along top of plate to be coated
  • Uniformly apply TiO2 suspension to edge of plate
  • 5 microliters per square centimeter
  • Distribute TiO2 over plate surface with stirring
    rod
  • Dry covered plate for 1 minute in covered petri
    dish

8
Procedure Deposition of TiO2 Film
  • Anneal TiO2 film on conductive glass
  • Tube furnace at 450 oC
  • 30 minutes
  • Allow conductive glass to cool to room
    temperature will take overnight
  • Store plate for later use

9
Procedure 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)

10
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 kimwipe

11
Procedure Carbon Coating the Counter Electrode
  • Apply light carbon film to second SnO2 coated
    glass plate on conductive side
  • Soft pencil lead, graphite rod, or exposure to
    candle flame

12
Procedure Assembling the Solar Cell
  • Place two binder clips on longer edges to hold
    plates together (DO NOT clip too tight)
  • Place 2-3 drops of iodide electrolyte solution at
    one edge of plates
  • Alternately open and close each side of solar
    cell to draw electrolyte solution in and wet TiO2
    film
  • Ensure all of stained area is contacted by
    electrolyte
  • Remove excess electrolyte from exposed areas
  • Fasten alligator clips to exposed sides of solar
    cell

13
Procedure Measuring the Electrical Output
  • Attach the black (-) wire to the TiO2 coated
    glass
  • Attach the red () wire to the counter electrode
  • Measure open circuit voltage and short circuit
    current with the multimeter.
  • For indoor measurements, can use halogen lamp
  • Make sure light enters from the TiO2 side
  • Measure current-voltage using a 1 kohm
    potentiometer
  • The center tap and one lead of the potentiometer
    are both connected to the positive side of the
    current
  • Connect one multimeter across the solar cell, and
    one lead of another meter to the negative side
    and the other lead to the load

14
Results
  • Open circuit voltage 0.388 V

15
Analysis Power
  • Maximum Power 21 mW
  • Active Area 0.7 in2 ? Max. power per unit area
    30 mW/in2

16
Questions
  • Approximate TiO2 particle size assume 25 nm
    diameter
  • Number of TiO2 units per nanoparticle
  • Volume of one nanoparticle 8.18 10-18 cm3
  • Density of TiO2 4 g/cm3 ? Mass of one
    nanoparticle 3.27 10-17 g
  • Molar mass of TiO2 79.87 g/mol ?moles of TiO2
    in one nanoparticle 4.10 10-19 moles
  • 4.10 10-19 moles 6.022 1023
    molecules/mole 2.48 105 TiO2 units per
    nanoparticle
  • Nanoparticle surface area per gram
  • Number of nanoparticles per gram 1/(3.27
    10-17) 3.06 1016 nanoparticles
  • Surface area of one nanoparticle 1.96 10-15
    m2
  • Surface area per gram 3.06 1016
    nanoparticles/gram 1.96 10-15
    m2/nanoparticle 60.0 m2/gram

17
Questions
  • Fraction of atoms that reside on the surface
  • Surface area of one particle 1.96 10-11 cm2
  • Approximate atoms per unit area 1015 atoms/cm2
  • Atoms on surface 1.96 10-11 cm2 1015
    atoms/cm2 1.96 104 atoms
  • Fraction of atoms on surface (1.96
    104)/(2.48 105) 0.079
  • Way to improve experiment
  • Filter raspberry juice using a better filter
    system
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