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Solar cell as a heat engine: energy–entropy analysis of photovoltaic conversion
Author(s) -
Markvart Tom
Publication year - 2008
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.200880460
Subject(s) - physics , detailed balance , ideal gas , photovoltaic system , energy transformation , heat engine , radiant energy , solar cell , radiative transfer , entropy (arrow of time) , thermal radiation , solar energy , energy conversion efficiency , photon , thermodynamics , radiation , solar cell efficiency , energy balance , optoelectronics , optics , ecology , biology
A thermodynamic theory for the voltage or free energy generated by a quantum solar energy converter which has recently been proposed, is developed here in a more direct and simpler way. We consider separately the luminescence and conversion of a single photon of the incident radiation. The energy/entropy balance for the conversion process yields an expression for the voltage in a form familiar from the classical thermodynamics of the work carried out by the heat engine. A similar balance for the absorption and emission of light gives an expression for the irreversible entropy generation which reduces the open circuit voltage generated by the solar cell. Detailed expressions for losses due to individual mechanisms, including non‐radiative recombination, are obtained with the use of an approximation where photons in the incident and emitted beams are modelled as an ideal two‐dimensional gas. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)