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Exploring Excitons and Solar Energy: Harnessing Light for Power Generation

This informative text delves into the concept of excitons in solar energy production, exploring how electrons can generate energy from sunlight. Covering energy band theory, the text discusses the challenges of the single electron approximation and the significance of exciton binding energy. It elaborates on the use of different materials to separate excitons and the drawbacks of first-generation silicon solar cells. Additionally, it delves into second-generation solar cells like multiple junction photovoltaic cells and thin film technology. The text introduces quantum dots, their sizes, and how they can accommodate varying numbers of electrons based on their dimensions. It also explains the structure and working principles of third-generation quantum dots, emphasizing their high efficiency in generating power from light. Through technical design capabilities, quantum dots can control voltage, current, and frequency selection, making them a promising technology for enhancing solar energy generation.

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Exploring Excitons and Solar Energy: Harnessing Light for Power Generation

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  1. Excitons and Solar Energy Shuhua Liang UTK Physics department

  2. Energy Problem • Full list • Rank Company Revenues Profits ($ millions) • 1 Exxon Mobil 339,938.0 36,130.0 • 2 Wal-Mart Stores 315,654.0 11,231.0 • 3 Royal Dutch Shell 306,731.0 25,311.0 • 4 BP 267,600.0 22,341.0 • 5 General Motors 192,604.0 -10,567.0 • 6 Chevron 189,481.0 14,099.0 • 7 DaimlerChrysler 186,106.3 3,536.3 • 8 Toyota Motor 185,805.0 12,119.6 • 9 Ford Motor 177,210.0 2,024.0 • 10 ConocoPhillips 166,683.0 13,529.0 • (from FORTUNE top 500 companies 2006)

  3. Solar Energy • (from GCEP)

  4. How to get energy from sun light? • Use electron! (by shuhua)

  5. Energy band theory • The problem of single electron approximation • In experiment people find structure in energy gap.

  6. Excition and binding energy • Binding energy • Reduced mass

  7. How to generate Current? • Use two different type of material to separate the exciton (electron-hole)

  8. The first generation Si Solar Cell

  9. The disadvantage of Si cell • Expensive $565.00 Weight: 28.00 lbs • Low efficiency (around 16%)

  10. Second generation solar cell 1)multiple junction photovoltaic cells :high efficiency :high cost (from Sonny X. Li ) 2)Thin film :low efficiency :low cost

  11. Quantum Dot Size: 2-10 nm Accommodate 5-1000electrons 2Dor 3D free electron model (depend on the shape) Structure: core&shell (from Evident Technologies ) Third Generation

  12. Larger and heavier quantum dots are at bottom How does it work?

  13. How does it work?

  14. High efficiency due to one photon can excite several electrons Energy gap decide the min frequency of light Can control the volt and current Why Quantum Dot is good?

  15. Technically we can design the size of quantum dot to design the gap width. (from google) Quantum Dot can select frequency

  16. Thank You

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