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Practical target values of Shockley–Read–Hall recombination rates in state‐of‐the‐art triple‐junction solar cells for realizing conversion efficiencies within 1% of the internal radiative limit
Author(s) -
Nakamura Tetsuya,
Imaizumi Mitsuru,
Akiyama Hidefumi,
Okada Yoshitaka
Publication year - 2020
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.3251
Subject(s) - recombination , radiative transfer , spontaneous emission , physics , limit (mathematics) , energy conversion efficiency , depletion region , luminescence , power density , recombination rate , atomic physics , power (physics) , optics , chemistry , optoelectronics , quantum mechanics , semiconductor , gene , mathematical analysis , laser , biochemistry , mathematics
In order to identify the cause of the difference between actual efficiency and the theoretical limit in state‐of‐the‐art triple‐junction solar cells, we investigate the internal luminescence efficiency in the depletion region ( η int dep ). The average internal luminescence efficiency of the whole subcell volume ( η int ¯ ) is obtained experimentally, and the η int dep is deduced by numerical calculations using rate equations. We find thatη int ¯ and η int dep agree well in the low‐recombination current regime including the maximum power point. This indicates that the non‐radiative recombination loss at the maximum power point strongly depends on the recombination in the depletion region. Furthermore, we determine the actual Shockley–Read–Hall recombination coefficient in the depletion region, A dep , which is proportional to the effective density of recombination centers. Our analysis reveals the target values of A dep required for realizing conversion efficiencies that are within 1% of the internal radiative limit. The analysis also clarifies the extent of reduction of the effective density of recombination centers (in the depletion region) that is required to realize a given target efficiency.