Design Flexibility of Ultrahigh Efficiency Four-Junction Inverted Metamorphic Solar Cells

Ryan M. France, John F. Geisz, Ivan Garcia, Myles A. Steiner, William E. McMahon, Daniel J. Friedman, Tom E. Moriarty, Carl Osterwald, J. Scott Ward, Anna Duda, Michelle Young, Waldo J. Olavarria

Research output: Contribution to journalArticlepeer-review

81 Scopus Citations


The inverted metamorphic solar cell has highly tunable bandgaps, in part due to the metamorphic subcells. Using phosphide-based compositionally graded buffers, we show a wide variety of GaInAs solar cells, ranging in bandgap from 1.2 to 0.7 eV. These metamorphic subcells are all high quality and can be used for a wide variety of multijunction designs. GaInAs solar cells with 0.70 eV bandgaps are developed using an InAsP buffer that extends beyond the InP lattice constant, allowing access to an additional 2 mA/cm2 of photocurrent at AM1.5D and 25 °C. This subcell is implemented into a four-junction inverted metamorphic solar cell combined with an appropriate antireflective coating, which increases the series-connected multijunction current by 0.5 mA/cm2 with respect to designs using 0.74-eV GaInAs. However, the optimal design depends on the spectrum and operating temperature. We show how the device flexibility can be used to fine-tune the design for various spectra in order to maximize energy yield for a given operating condition. One-sun devices achieve 35.3 ± 1.2% efficiency under the AM0 spectra and 37.8 ± 1.2% efficiency under the global spectra at 25 °C. Concentrator devices designed for elevated operating temperature achieve 45.6 ± 2.3% peak efficiency under 690× the direct spectrum and 45.2 ± 2.3% efficiency at 1000× and 25 °C. Device optimization is performed for the direct spectrum on 1-sun devices with 2% shadowing, which achieve 39.8 ± 1.2% efficiency under the direct spectrum at 1 sun, highlighting the excellent performance and bandgap tunability of the four-junction inverted metamorphic solar cell.

Original languageAmerican English
Article number7359108
Pages (from-to)578-583
Number of pages6
JournalIEEE Journal of Photovoltaics
Issue number2
StatePublished - Mar 2016

Bibliographical note

Publisher Copyright:
© 2015 IEEE.

NREL Publication Number

  • NREL/JA-5J00-66093


  • Four-junction solar cells
  • Inverted metamorphic multijunction


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