Single-junction flat-plate terrestrial solar cells are fundamentally limited to about 30% solar-to-electricity conversion efficiency, but multiple junctions and concentrated light make much higher efficiencies practically achievable. Until now, four-junction III–V concentrator solar cells have demonstrated the highest solar conversion efficiencies. Here, we demonstrate 47.1% solar conversion efficiency using a monolithic, series-connected, six-junction inverted metamorphic structure operated under the direct spectrum at 143 Suns concentration. When tuned to the global spectrum, a variation of this structure achieves a 1-Sun global efficiency of 39.2%. Nearly optimal bandgaps for six junctions were fabricated using alloys of III–V semiconductors. To develop these junctions, it was necessary to minimize threading dislocations in lattice-mismatched III–V alloys, prevent phase segregation in metastable quaternary III–V alloys and understand dopant diffusion in complex structures. Further reduction of the series resistance within this structure could realistically enable efficiencies over 50%.
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The authors thank W. Olavarría and M. Young for cell fabrication. I. Garcia, N. Jain and E. Perl developed the initial components of the 6J IMM as referenced. We thank D. Friedman for managerial support and helpful discussions. J. Olson, S. Kurtz and M. Wanlass laid the groundwork for all multijunction solar cells at NREL. Thanks to J. K. Geisz for help with photography and A. Hicks for graphics design. This work was authored by the National Renewable Energy Laboratory, operated by Alliance for Sustainable Energy, LLC, for the US Department of Energy (DOE) under Contract no. DE-AC36-08GO28308. Funding was provided by the US Department of Energy Efficiency and Renewable Energy Solar Energy Technologies Office under Agreement Number 30293. The views expressed herein do not necessarily represent the views of the DOE or the US Government.
The authors declare no competing interests.
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Geisz, J.F., France, R.M., Schulte, K.L. et al. Six-junction III–V solar cells with 47.1% conversion efficiency under 143 Suns concentration. Nat Energy 5, 326–335 (2020). https://doi.org/10.1038/s41560-020-0598-5
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