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Open AccessFeature PaperArticle

Super-Multi-Junction Solar Cells—Device Configuration with the Potential for More Than 50% Annual Energy Conversion Efficiency (Non-Concentration)

1
Toyota Technological Institute, Nagoya 468-8511, Japan
2
Organization for Promotion of Tenure Track, University of Miyazaki, Miyazaki 889-2192, Japan
3
Faculty of Engineering, University of Miyazaki, Miyazaki 889-2192, Japan
*
Author to whom correspondence should be addressed.
Appl. Sci. 2019, 9(21), 4598; https://doi.org/10.3390/app9214598
Received: 20 September 2019 / Revised: 19 October 2019 / Accepted: 20 October 2019 / Published: 29 October 2019
The highest-efficiency solar cell in the efficiency race does not always give the best annual energy yield in real world solar conditions because the spectrum is always changing. The study of radiative coupling of concentrator solar cells implies that efficiency could increase by recycling the radiative recombination generated by the surplus current in the upper junction. Such a configuration is called a super-multi-junction cell. We expand the model in the concentrator solar cell to a non-concentrating installation. It is shown that this super-multi-junction cell configuration is robust and can keep maximum potential efficiency (50% in realistic spectrum fluctuation) for up to 10 junctions. The super-multi-junction cell is also robust in the bandgap engineering of each junction. Therefore, a future multi-junction may not be required for tuning the bandgap to match the standard solar spectrum, as well as relying upon artificial technologies such as epitaxial lift-off (ELO), wafer-bonding, mechanical-stacking, and reverse-growth, but merely uses upright and lattice-matching growth technologies. We present two challenging techniques; one is the optical cap layer that may be the directional photon coupling layer in the application of the photonics technologies, and another is the high-quality epitaxial growth with almost 100% radiative efficiency. View Full-Text
Keywords: tandem; solar cell; multi-junction; performance ratio; spectrum; modeling; radiative coupling; luminescence coupling tandem; solar cell; multi-junction; performance ratio; spectrum; modeling; radiative coupling; luminescence coupling
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Araki, K.; Ota, Y.; Saiki, H.; Tawa, H.; Nishioka, K.; Yamaguchi, M. Super-Multi-Junction Solar Cells—Device Configuration with the Potential for More Than 50% Annual Energy Conversion Efficiency (Non-Concentration). Appl. Sci. 2019, 9, 4598.

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