Joule
Volume 6, Issue 5, 18 May 2022, Pages 1121-1135
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Article
Triple-junction solar cells with 39.5% terrestrial and 34.2% space efficiency enabled by thick quantum well superlattices

https://doi.org/10.1016/j.joule.2022.04.024Get rights and content
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Highlights

  • Strain-balanced quantum wells modify the bandgap of a GaAs-based solar cell

  • Optically thick devices are shown with excellent carrier collection and voltage

  • Three-junction solar cells incorporating quantum wells achieve record efficiency

Context & scale

High-efficiency solar cells are demanded by all applications of photovoltaics, including terrestrial and space power generation, thermal energy conversion via thermophotovoltaics, and transmission via laser power conversion. Here, we demonstrate triple-junction III-V solar cells with higher efficiencies than previous record-efficiency six-junction devices. The devices incorporate high-performance thick GaInAs/GaAsP superlattices to enable an optimal bandgap combination. These cells are most useful for area-constrained terrestrial applications and low-radiation space missions, where efficiency is critical. As these are the highest efficiency one-sun solar cells as of this writing, these cells also set a new standard for achievable efficiency across all photovoltaic technologies.

Summary

Multijunction solar cell design is guided by both the theoretical optimal bandgap combination as well as the realistic limitations to materials with these bandgaps. For instance, triple-junction III-V multijunction solar cells commonly use GaAs as a middle cell because of its near-perfect material quality, despite its bandgap being higher than optimal for the global spectrum. Here, we modify the middle cell bandgap using thick GaInAs/GaAsP strain-balanced quantum well (QW) solar cells with excellent voltage and absorption. These high-performance QWs are incorporated into a triple-junction inverted metamorphic multijunction device consisting of a GaInP top cell, GaInAs/GaAsP QW middle cell, and lattice-mismatched GaInAs bottom cell, each of which has been highly optimized. We demonstrate triple-junction efficiencies of 39.5% and 34.2% under the AM1.5 global and AM0 space spectra, respectively, and the global efficiency is higher than previous record six-junction devices.

Keywords

multijunction solar cell
quantum well
superlattice
metamorphic
high efficiency
space photovoltaics

Data and code availability

The data generated in this study is included in the manuscript and supplemental information and will be made available upon request.

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