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Gratzel Solar Cell
Transcript of Gratzel Solar Cell
Nanocrystals (1-100 nm)=Bonding points for dye
Create surface area
Small band gap
10-nm-thick ( Gratzel and O'regan, 1991) One option available
Not the main factor Chlorophyll dye from spinach
Carboxyl groups capable of chelating to the surface of the TiO2 particles. Background Info :
TiO2 coated electrode (Photons entry)
Organic dye particles (electron donor) are chelated into TiO2 layer
Photons excite electrons present in dye
Electrons jump to higher energy levels and are released to travel through TiO2 semiconductor
Electrons reach transparent conducting plate and travel into the circuit
Manuela Restrepo & Lizet Rodriguez
Delcastle Technical High School
April 12, 2011
Funded by NCCVT and Mr. Gross Dye #2 Passion Fruit Tea
Anthocyanin (Fernando and Senadeera, 2008)
Hydroxyl groups capable of chelating to TiO2 surface. Tin Dioxide is what makes slides conductive continue... Hole left by absence of electron is transferred to electrolyte
Electrolyte is oxidized
Oxydized electrolyte brings this positive charge to the counter electrode where it "meets" with a returning electron
Electrolyte is returned to its reduced form
The circuit is closed and electricity is produced electron donor, in this case we used iodide Problem/Research TiO2 consistency and application was key
More surface area=more bonding points
Very thick TiO2= Wide band gap, not enough photons
Very thin TiO2= Not many crystals
Researchers have studied multiple application methods and what gives the highest current Hypothesis: *As different methods of TiO2 deposition are used to achieve maximum allowed thickness, the current achieved on a dye sensitized nanocrystalline solar cell increases. Results A balanced TiO2 solution was made and a uniform application method was found. We wanted a deposition that would allow for crystal formation, small band gap, and light absorption. Method After many TiO2 powder to acetone, water, and surfactant ratios, the perfect consistency was achieved!
The next significant factor was using an application method that would allow the TiO2 to have the perfect balance stated in our problem and hypothesis. TiO2 Solution
1g of TiO2 grounded with mortar and pestle to obtain nanoparticles
.2ml of acetone/water solution
5 increments of .2ml of water TiO2 Application Methods Stirring rod Paint Brush Drop Casting Microscope Glass slide Uneven, striations, and cracked when heated
.035 mA current was achieved Coating had uneven stripes and it was too thin.
.023 mA current was achieved Completely unsuccesful due to lack of vaccuum and uncontrolled temperature. Yielded no results. Coating was completely smooth and even.
It had the thickness of the tape guide. .1 mA with chlorophyl dye
3.5 mA with anthocyanine dye Anthocyanine dye was only used on the slide where TiO2 was applied with the glass slide. This is the solar cell that yielded the highest current.
Chlorophyl dye didn't seem to yield high results. mA of current using glass slide application and anthocyanin dye Results Carbon coated electrode TiO2 coated electrode Passion fruit tea/Anthocyanine dye Assembled solar cell Solar cell under projector light (artificial sun) current in mA as it increase to about 3.5 mA (not pictured) Also known as positive charge not a typical "linear" hypothesis because we were not testing a linear variable. Our goal was to achieve the ideal TiO2. VERY IMPORTANT!!!! Carbon coated electrode Electron injection Discussion Simple results!!
"Balance" was achieved and we got a current.
Current increased as a better TiO2 coat was achieved.
We were not able to prove how efficient the cell was. Results and research evaluation WHEN IT COMES TO LUX CONVERSION, DO NOT TRUST THE INTERNET! To achieve the best TiO2 consistency, the real key was the surfactant.
Surfactant= "controlled thickener"
It became a common concensus that a thin paste (paint like) TiO2 was the most effective.
This is the consistency we used and it's what yielded the highest results. CuSO4 solution that absorbs heat Difficulties/Future Questions What is the "perfect" consistency/application method?
What is the main factor contributing to effectiveness. (band gap, crystal formation, or light absorption)?
Will a combination of dies increase the effectiveness of the solar cell?
Do dye particles bond to certain points in the TiO2 depending on their bonding groups? (-OH and -COOH) ?
Is this what could explain the better performance of two dyes? Importance Understanding of solar energy significance.
Future pioneers in solar technology.
Acknowledgements NCCVT School District
Ms. Swain (working time :D )
Dr. Shah and his students References Gratzel, Michael, and Brian O'regan. "A low-cost, high-efficiency solar cell
based on dye-sensitized colloidal TiO2 films." Nature . N.p., 24 Oct. 1991.
Web. 13 Apr. 2011. converted to triiodide (Denker, 2007) Denker. "Titanium Dioxide Dye Sensitized Solar cells." Bulletin. N.p., 14 July
2007. Web. 13 Apr. 2011. Fernando, C, and R Senadeera. " Natural anthocyanins as photosensitizers for
dye-sensitized solar devices." IAS. N.p., 30 July 2008. Web. 13 Apr. 2011. special bond at multiple points to a metal ion