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Nanotechnology : Applications in Energy –Solar Cells

Nanotechnology : Applications in Energy –Solar Cells. Solar energy is seen as the cleanest, most abundant, renewable energy source available today. 

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Nanotechnology : Applications in Energy –Solar Cells

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  1. Nanotechnology:Applications in Energy –Solar Cells • Solar energy is seen as the cleanest, most abundant, renewable energy source available today.  • The energy output of a 1 KW solar energy unit is equivalent to the burning of 170 pounds of coal and 300 pounds of carbon dioxide being released into the atmosphere.

  2. Solar energyDo we have enough?

  3. Do weuse it?(the situation isn’t getting any better)

  4. Is it costeffective?Economics of solar energy

  5. Conventional solar cells have two main drawbacks • Inefficient and expensive • Inefficiency, unavoidable with silicon cells. Why? • Incoming photons, must have the right band gap energy, to knockout an electron. If the photon has less energy then it will pass through. If it has more energy then extra energy wasted as heat. • These two effects causes loss of around70 % of the energy incident on the cell. • So, current solar cells cannot convert all the incoming light into usable energy

  6. Best Research Cell Efficiencies

  7. Using the Sun’s Energy • The basic processes in converting the sun’s energy into usable electricity are: • Absorption of light. • Creation of free charge carriers: e-and h+. • Transport and collection of charge.

  8. Solar Cell Technologies

  9. Grätzel – Inventor Michael Grätzel and his researchers at Swiss Federal Institute of Technology in Switzerland Dye-sensitized solar cell They are dye-sensitized titanium dioxide (TiO2) photo-electrochemical cells that directly convert solar energy to electrical energy

  10. Dye-sensitized solar cell • The dye‐sensitized solar cells (DSSC) provides a technically and economically credible alternative concept to present day p–n junction photovoltaic devices. • In contrast to the conventional systems where the semiconductor assume both the task of light absorption and charge carrier transport the two functions are separated here. Light is absorbed by a sensitizer, which is anchored to the surface of a wide band semiconductor. • Charge separation takes place at the interface via photo‐induced electron injection from the dye into the conduction band of the solid.

  11. A cross section of the dye sensitized solar cell

  12. How do they Work? 1- Sunlight energy (photoelectric effect) strike dye molecules, exciting electrons

  13. How do they Work? 2- The excited electrons move through the conduction band of TiO2 up to the conducting plate. Flow of electricity is initiated.

  14. How do they Work? 3- The dye is regenerated by the Iodide molecule giving up one of its electrons to form triiodide (oxidation occurs).

  15. How do they Work? 4- The triiodide molecule is reduced back to iodide by an electron at graphite conducting plate.

  16. Nanostructured Solar Cell

  17. Dye-sensitized solar cell

  18. Dye-sensitized solar cell

  19. CdSeSensitizers/Nano TiO2

  20. References • Center for Nanotechnology Education and Utilization (CNEU) Regional Center. The Pennsylvania State University • David F. Kelley University of California, Merced. • Education and Utilization (CNEU) Regional Center. • Nanotechnology Applications and Career Knowledge (NACK) National Center. The Pennsylvania State University • http://people.bath.ac.uk/pysabw/research/scell/dssc.htm • Grätzel, M. (2001). Photoelectrochemical Cells. Nature, 414 (15), 338-44. • http://unit.aist.go.jp/energy/groups/img/slecg_photocell.jpg

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