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Detailed Balance Limit of Efficiency of p-n Junction Solar Cells

Detailed Balance Limit of Efficiency of p-n Junction Solar Cells. Journal By: William Shockley and Hans J. Queisser Presented By: Wai Son (Wilson) Ko March 1, 2009. Outline. Introduction Derivation of Solar Cell Efficiency from Thermodynamics Assumptions and Setups

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Detailed Balance Limit of Efficiency of p-n Junction Solar Cells

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  1. Detailed Balance Limit of Efficiency of p-n Junction Solar Cells Journal By: William Shockley and Hans J. Queisser Presented By: WaiSon (Wilson) Ko March 1, 2009

  2. Outline • Introduction • Derivation of Solar Cell Efficiency from Thermodynamics • Assumptions and Setups • Solar Cell Limiting Efficiency • Conclusion EE235 Presentation – Detailed Balance Limit of Efficiency

  3. Introduction Can we still improve solar cell efficiency?? 1961 1950s EE235 Presentation – Detailed Balance Limit of Efficiency

  4. Assumptions and Setups EE235 Presentation – Detailed Balance Limit of Efficiency

  5. Assumptions • Sun and solar cells are blackbodies • Photon with E>Eg gives rise to one pair of electron and hole • Loss is radiative recombination only Source: wikipedia EE235 Presentation – Detailed Balance Limit of Efficiency

  6. Setups Blackbody Absorption @ Tc = 300K Blackbody Radiation @ Tc= 300K Blackbody Radiation @ TS = 6000K EE235 Presentation – Detailed Balance Limit of Efficiency

  7. Solar Cell Limiting Efficiency EE235 Presentation – Detailed Balance Limit of Efficiency

  8. Geometrical Factor Geometrical factor to account for absorbing limited fraction of solar radiation D = 1.39 million km L = 149 million km EE235 Presentation – Detailed Balance Limit of Efficiency

  9. Blackbody Radiation • # of photons per time and surface area absorbed • # of photons per time and surface area radiated • Total solar power incident on the cell Geometrical factor to account for absorbing limited fraction of solar radiation W. Shockley and H. Queisser, J. Appl. Phys., (1961) EE235 Presentation – Detailed Balance Limit of Efficiency

  10. Diode I-V Characteristics • Generation = Recombination + Extraction Rearrange W. Shockley and H. Queisser, J. Appl. Phys., (1961) EE235 Presentation – Detailed Balance Limit of Efficiency

  11. Theoretical Maximum Efficiency • Define to be the open-circuit voltage • Maximum power outputs at the point such that • Therefore, • Efficiency: W. Shockley and H. Queisser, J. Appl. Phys., (1961) EE235 Presentation – Detailed Balance Limit of Efficiency

  12. Theoretical Maximum Efficiency • η=30.4% • @ Eg = 1.322eV • Silicon: • η=29.5% EE235 Presentation – Detailed Balance Limit of Efficiency

  13. Conclusions • Maximum theoretical efficiency can be calculated from thermodynamics • Assuming blackbody radiation, absorption • η=30.4% • @ Eg = 1.322eV EE235 Presentation – Detailed Balance Limit of Efficiency

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