Design Flexibility of Ultra-High Efficiency 4-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 conferencePaperpeer-review

20 Scopus Citations


We present recent improvements to the 4-junction inverted metamorphic solar cell. The device now includes a (Ga)InAsP buffer that transitions to lattice constants greater than InP, which allows access to GaInAs subcells with bandgaps < 0.74 eV and an additional 2 mA/cm2 of bottom junction photocurrent at AM1.5D. 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. 1-sun devices achieve 35.3% efficiency under the AM0 spectrum and 37.8% efficiency under the global spectrum at 25°C. Concentrator devices achieve 45.7% peak efficiency under 234x the direct spectrum and maintain over 45% efficiency at 700x at 25°C. Other device improvements include a 4-layer anti-reflection coating with low power loss, and reduced series resistance.

Original languageAmerican English
Number of pages3
StatePublished - 14 Dec 2015
Event42nd IEEE Photovoltaic Specialist Conference, PVSC 2015 - New Orleans, United States
Duration: 14 Jun 201519 Jun 2015


Conference42nd IEEE Photovoltaic Specialist Conference, PVSC 2015
Country/TerritoryUnited States
CityNew Orleans

Bibliographical note

Extended version published in the IEEE Journal of Photovoltaics: see NREL/JA-5J00-66093

NREL Publication Number

  • NREL/CP-5J00-63574


  • 4-junction solar cells
  • inverted metamorphic multijunction


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