Counter electrode

Atul kumar12307005

Gratzel Cell • Photo-electrochemical Cell

– Artificial photosynthesis

SnO2

SnO2

Electrolyte

TiO2 10m

Platinum

Dye/biopolymer/quantum dots

Dye-sensitized solar cells: Dye-sensitized solar cells: ComponentsComponents

1. Granular TiO2 forming a nanoporous structure.

2. A dye, which is a light sensitive substance spread on the TiO2 surface.

3. A redox couple (I-/I3-), located in the space between the dye and the cathode.

4. Fto coated front glass and counter electrode coated back substrate

TiO2

Electrolyte

Dye-sensitized solar cells: OperationDye-sensitized solar cells: Operation

1. Dye electrons are excited by

solar energy absorption.2. They are injected into the

conduction band of TiO2.

3. Get to counter-electrode (cathode) through the external circuit.

4. : Redox regeneration at the counter-electrode (oxidation).

5. : Dye regeneration reaction (reduction).

6. Potential used for external work:

--3 I32I e

e2II3 -3

-

redoxFext VEV

Red=I-Ox =I3-

Ionic Liquid

Nanocrystalline Solar Cell: Materials

Materials:1. F-SnO2glass slides2. Iodine and triIodide

electrolyte3. Colloidal Titanium Dioxide

Powder4. Ruthenium n3 dye.5. Counter electrode

Counter electrodeThe counter electrode is one of the most important components of dssc, since1.It has the function of reducing the oxidized mediator species 2. Transferring the electrons from load to electrolyte/Collecting the holes from the hole transporting material. 3.Sufficiently corrosion-resistant to electrolyte. 4.In equivalent circuit of dssc the counter electrode constant phase element, charge transfer resistance of counter electrode.

the choice of the counter electrode depends as1. platinum is a precious metal

2.Carbon-based materials, and other platinum-free catalytic layers, deposited over different substrates, such as metal foils and plastic sheets are tried.

.

Carbon counter electrode dssc

Method for deposition of counter electrode

Pt was electrodeposited from a solution containing 10 mM H2PtCl6 and 0.5 M KCl in a three-electrode cell with•indium tin oxide (ITO) glass working electrode,•Pt mesh auxiliary electrode,• Ag/AgCl reference electrode.

Technique used to deposit the pt using •Chronopotentiometry

ChronopotentiometryChronopotentiometry (CP) is the most basic constant current experiment where step current is applied across an electrochemical cell.The galvanostat uses a three electrode configuration. The basis of controlled current experiments is that a redox (electron transfer) reaction that must occur at the surface of the working electrode in order to support the applied current applications of this is constant current electrolysis such as electrodeposition

Pt deposition

10mM H2PtCl6.6H2o,10mM KCl are taken in 20 ml H2O to from a solution for electrodeposition of

Pt .

Pt deposition for 150s using chronopotentiometry

pt deposition for 600s using chronopotentiometry

pt deposition for 300s using chronopotentiometry

Counter electrode characterization:CV

Application of a reversing linear sweep

If an electro active species is present we obtain a Faradaic current, summed to the background charging current

I = IC+If

Counter electrode

• Good catalytic activity for triiodide to iodide conversion• Low resistance• Pt• Au• Carbon • WO2

• Nb2O5

• Cobalt

CV

E° = (Epa + Epc)/2

Ep = Epa - Epc = 59mV/n

The deposited pt are checked for the catalytic activity by cv in the solution of 10mM LiI, 1mM I, 0.1mM LiClO4 in 25

ml acetonitrile

Counter electrode characterization

Cv of pt deposited (600s) Cv of pt deposited (600s)

Cv of aluminium doped zno coated glass substrate

Carbon counter electrode

We also prepared carbon counter electrode by depositing carbon on tco glass we prepared two carbon glass

plate by depositng carbon for 10 second dark and 2 second light

deposit.and took cv for checking catalytic activity of carbon coted

counter electrode.

Cv Carbon thick deposition for 10 second

Cv Carbon thin deposition for 2 second

Fabrication of dssc

Procedure:• Add 1 gram of TiO2 (in 1 ml H2O) of a drop of

acetic acid (ph3-4) in a mortar and pestle.• Grinding for 30 minutes will produce a lump

free paste.• 1 drop of a surfactant is then added

(mercapta propanoic acid).

Semiconductor electrode• Support for dye adsorption• Wide bandgap semiconductor • High surface area• Good electron conductivity• Low recombination• Nanoparticles• Nanotubes• Double layer• ZnO

Way towards higher efficiency

• Better light absorber• Solid electrolyte • Cheaper Counter electrode material• Suitable electrode • Simple and cheap TCO material• Higher efficiency to be suitable for production

in large scale

Coating the Cell• After testing to determine which

side is conductive, one of the glass slides is then masked off 1-2 mm on THREE sides with masking tape. This is to form a mold.

• A couple of drops if the titanium dioxide suspension is then added and distributed across the area of the mold with a glass rod.

• The slide is then set aside to dry for one minute.

• After the first slide has dried the tape can be removed.

• The titanium dioxide layer needs to be heat sintered and this can be done by using a hot air gun that can reach a temperature of at least 450 degrees Celsius.

• This heating process should last 30 minutes.

Dye Absorption and Coating the Counter Electrode

• Allow the heat sintered slide to cool to room temperature.

• Once the slide has cooled, place the slide face down in the filtered dye and allow the dye to be absorbed for 5 or more minutes.

•While the first slide is soaking, determine which side of the second slide is conducting.•Place the second slide over an open flame and move back and forth.•This will coat the second slide with a carbon catalyst layer

Assembling the Solar Cell• After the first slide had

absorbed the dye, it is quickly rinsed with ethanol to remove any water. It is then blotted dry with tissue paper.

• Quickly, the two slides are placed in an offset manner together so that the layers are touching.

• Binder clips can be used to keep the two slides together.

•One drop of a liquid iodide/iodine solution is then added between the slides. Capillary action will stain the entire inside of the slides

Preparation of Electrolyte Solution

Electrolyte solution1. Measure out 25-ml of acetonitrile.2. Weigh out 0.317-g of I2 or 0.05mM, add it to the acetonitirle

and stir.3. Weigh out 1.6731 g of LiI 0.5mM and add it to the same.4. Stir and sore in a dark container with a tight lid.5. 0.3mM N3 dye was taken and added to 10ml ethanol. N3 -

RuL₂(NCS) ₂(L=2,2’-bipyridyl-4,4’-dicarboxylic acid)

ReferencesElectrochimica Acta 51 (2006) 3814–3819 Electrodeposited Pt for cost-efficient and flexible dye-sensitized solar cells Seok-Soon Kim, Yoon-Chae Nah, Yong-Young Noh, Jang Jo, Dong-Yu KimDye-sensitized solar cells Michael Grätzel∗Laboratory for Photonics and Interfaces, Swiss Federal Institute of Technology, CH-1015 Lausanne, Switzerland Journal of Photochemistry and Photobiology C: Photochemistry Reviews 4 (2003) 145–153Takechi, K., Muszynski, R., Kamat, PV. Fabrication procedure of dye-sensitized solar cells (http://www.nd.edu/~pkamat/pdf/solarcell.pdf) B. O’Regan, M. Grätzel, Nature 335 (1991) 737; M. Grätzel, Nature 414 (2001) 338–344.http://chemwiki.ucdavis.edu/Analytical_Chemistry/Instrumental_Analysis/Cyclic_Voltammetry

http://www.basinc.com/mans/EC_epsilon/Techniques/CPot/cp.html