Solar Cells -- Faissal's Presentation to Dorsinville Group and Guests, on Friday 8th October 2010


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Solar Cells -- Faissal's Presentation to Dorsinville Group and guests, on Friday 8th October 2010

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Solar Cells -- Faissal's Presentation to Dorsinville Group and Guests, on Friday 8th October 2010

  1. 1. Solar Cells Quantum Dot Enhanced SWCNT-Polymeric Solar Cells M. Faisal Halim Prof. Dorsinville, Walser, Hovhannisyan
  2. 2. What is a Solar Cell? <ul><li>A devices that generates electricity using light. </li></ul><ul><li>A Photovoltaic device generates a voltage when illuminated. </li></ul>Source: 8th October, 2010
  3. 3. Why Solar Cells? <ul><li>Tremendous potential for generating electricity </li></ul><ul><li>Government thrust: Green economy initiatives </li></ul><ul><li>Market forces: Other fuel sources are scarce resources </li></ul>
  4. 4. Current Solar Cells use Crystalline Technology <ul><li>Disadvantages of Crystalline Technology </li></ul><ul><li>Crystals need to be grown – expensive process </li></ul><ul><li>Lack of flexibility </li></ul><ul><li>Polycrystalline cells lack efficiency </li></ul><ul><li>Challenges in fabrication </li></ul>
  5. 5. Nanocrystal-Polymer Hybrid Solar Cells <ul><li>Advantages </li></ul><ul><li>Cheap </li></ul><ul><li>Mechanically Flexible </li></ul><ul><li>High Efficiency </li></ul><ul><li>Solution Processible </li></ul><ul><ul><li>Can take Advantage of Molecular Self Assembly </li></ul></ul><ul><ul><li>Processes are highly scalable </li></ul></ul><ul><li>Ease of Fabrication </li></ul><ul><li>Low Toxicity of Processing Methods </li></ul>
  6. 6. Basic Solar Cell Architecture Source: 8th October, 2010 Source: Solar Energy Materials and Solar Cells Volume 87, Issues 1-4, May 2005, Pages 733-746 Photo Active Layer:
  7. 7. <ul><li>Absorbs light and produces an electric voltage. </li></ul><ul><li>Quantum Dots (QD) absorb light </li></ul><ul><li>Carbon Nanotubes (SWCNT): conduct electrons from QD to cathode </li></ul><ul><li>P-type polymer (P3OT) conducts holes to anode </li></ul><ul><li>Area of interest </li></ul>Photo Active Layer Source: Solar Energy Materials and Solar Cells Volume 87, Issues 1-4, May 2005, Pages 733-746
  8. 8. Tasks Involved <ul><li>Material Synthesis </li></ul><ul><ul><li>Synthesis </li></ul></ul><ul><ul><li>Characterization: ABS, PL, Z-Scan </li></ul></ul><ul><li>Deposition of the Active Layer </li></ul><ul><ul><li>Synthesis </li></ul></ul><ul><ul><li>Characterization: ABS, PL, Z-Scan, Film Thickness, Film Surface Morphology, Film Uniformity </li></ul></ul><ul><li>Device Fabrication </li></ul><ul><ul><li>Synthesis </li></ul></ul><ul><ul><li>Characterization: VI Characteristics, Response to Light </li></ul></ul>
  9. 9. Tasks: Material Synthesis <ul><li>Synthesis of CdSe Quantum Dots </li></ul><ul><li>Purification of Single Walled Carbon Nanotubes (SWNT) </li></ul><ul><li>Making Solutions of P3OT Polymer </li></ul><ul><li>Making Solutions of PEDOT:PSS </li></ul><ul><li>Making Appropriate Solution Mixtures </li></ul>
  10. 10. Tasks: Deposition of Active Layer <ul><li>Appropriate Solution Mixtures Spin Coated. Films are of: </li></ul><ul><ul><li>Optical Quality </li></ul></ul><ul><ul><li>Uniform Thickness </li></ul></ul><ul><ul><li>Uniform Composition </li></ul></ul><ul><li>Films Grown Layer by Layer </li></ul><ul><ul><li>Deposition at 80 RPM </li></ul></ul><ul><ul><li>Coating, 10 secs, 1000 RPM </li></ul></ul><ul><ul><li>Drying, 200 RPM </li></ul></ul><ul><li>Films of Different Materials Deposited Sequentially </li></ul>
  11. 11. Tasks: Device Fabrication <ul><li>Spin Coating PEDOT:PSS onto ITO Coated Substrate </li></ul><ul><li>Spin Coating Active Layer Material </li></ul><ul><li>Vapor Depositing Al electrodes </li></ul>
  12. 12. CdSe Quantum Dot Synthesis <ul><li>CdSe QD Preparation 55 degrees Celcius Relatively Low Toxicity Materials: </li></ul><ul><li>Add Decylamine to Aqueous CdNTA </li></ul><ul><li>Add Aqueous Na 2 SeSO 3 </li></ul><ul><li>Add Toluene </li></ul><ul><li>CdSe QDs Migrate to the Toluene Phase </li></ul><ul><li>Add a Polymer Solution to Preserve QDs </li></ul>Source: Published online: 25 January 2004; doi:10.1038/nmat1056 Absorption Spectrum of CdSe QDs (aq)
  13. 13. Carbon Nanotube Purification <ul><li>Carbon Nanatubes Purchased in Impure Form. Purification Removes: </li></ul><ul><ul><li>Soot ( 470 o C in Oven, in Air ) </li></ul></ul><ul><ul><li>Metal Catalyst (Sonicating in HCl) </li></ul></ul><ul><ul><li>HCl (Sonicating and Centrifuging in DI Water) </li></ul></ul>Absorption Spectrum of SWCNTs (aq)
  14. 14. Active Layer Film <ul><li>Optical Quality </li></ul><ul><li>Uniform Thickness </li></ul><ul><li>Homogeneous </li></ul>Absorption Spectrum of 6 Layer Film of SWCNT in P3OT
  15. 15. Z-Scan Characterization <ul><li>Open Aperture </li></ul><ul><ul><li>Measures Multi-Photon Absorption </li></ul></ul><ul><ul><li>Measures Saturable Absorption </li></ul></ul><ul><li>Closed Aperture </li></ul><ul><ul><li>Measures Refractive Index as a Function of Intensity </li></ul></ul><ul><ul><li>Can be used as a measure of Optical Activity </li></ul></ul>
  16. 16. What the Measurements Will Tell Us <ul><li>Absorption Spectra </li></ul><ul><ul><li>Exciton Peak Wavelength </li></ul></ul><ul><li>Fluorescence Spectra </li></ul><ul><ul><li>Quantum Dot Size </li></ul></ul><ul><ul><li>Quantum Dot Surface Roughness </li></ul></ul><ul><li>Open Aperture Z-Scan </li></ul><ul><ul><li>Evidence of Excitation of Charge Carriers </li></ul></ul><ul><li>Closed Aperture Z-Scan </li></ul><ul><ul><li>Optical Response of Material in Resonant and Non-Resonant Wavelength Regimes </li></ul></ul>
  17. 17. How We May Use The Experimental Data <ul><li>The data will influence how and what parameters in the solar cells we optimize: </li></ul><ul><li>Surfactant, for: </li></ul><ul><ul><li>QD Surface Passivation </li></ul></ul><ul><ul><li>QD Shape </li></ul></ul><ul><ul><li>QD Size </li></ul></ul><ul><ul><li>QD’s Electrical Contact with Carbon Nanotubes </li></ul></ul><ul><ul><li>QD Surface roughness </li></ul></ul><ul><li>Carbon Nanotube, for: </li></ul><ul><ul><li>Diameter </li></ul></ul><ul><li>Polymer, for: </li></ul><ul><ul><li>Chain Length </li></ul></ul><ul><ul><li>Number of Side Chains </li></ul></ul><ul><ul><li>Functional Groups </li></ul></ul><ul><ul><li>Conductivity </li></ul></ul>
  18. 18. Other Experiments <ul><li>Third Order Nonlinear measurements performed for novel polymers </li></ul><ul><li>Possible Application in all-optical switching </li></ul><ul><li>Collaborative project with Professor Ogawa, Universidad Nacional Autónoma de México </li></ul>Source: Dyes and Pigments Volume 88, Issue 2, February 2011, Pages 129-134
  19. 19. Questions? <ul><li>End </li></ul>