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Fundamental losses in solar cells
Author(s) -
Hirst Louise C.,
EkinsDaukes Nicholas J.
Publication year - 2011
Publication title -
progress in photovoltaics: research and applications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.286
H-Index - 131
eISSN - 1099-159X
pISSN - 1062-7995
DOI - 10.1002/pip.1024
Subject(s) - carnot cycle , thermalisation , solar energy , physics , absorption (acoustics) , free carrier absorption , computational physics , solar cell , thermal , optics , optoelectronics , wavelength , thermodynamics , electrical engineering , engineering
This paper considers intrinsic loss processes that lead to fundamental limits in solar cell efficiency. Five intrinsic loss processes are quantified, accounting for all incident solar radiation. An analytical approach is taken to highlight physical mechanisms, obscured in previous numerical studies. It is found that the free energy available per carrier is limited by a Carnot factor resulting from the conversion of thermal energy into entropy free work, a Boltzmann factor arising from the mismatch between absorption and emission angles and also carrier thermalisation. It is shown that in a degenerate band absorber, a free energy advantage is achieved over a discrete energy level absorber due to entropy transfer during carrier cooling. The non‐absorption of photons with energy below the bandgap and photon emission from the device are shown to be current limiting processes. All losses are evaluated using the same approach providing a complete mathematical and graphical description of intrinsic mechanisms leading to limiting efficiency. Intrinsic losses in concentrator cells and spectrum splitting devices are considered and it is shown that dominant intrinsic losses are theoretically avoidable with novel device designs. Copyright © 2010 John Wiley & Sons, Ltd.