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Multijunction Solar Cells Improved With Graded Buffer Bragg Reflectors

National Renewable Energy Laboratory

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Technology Marketing Summary

Ultra-efficient III-V multijunction solar cells are finding increasing viability in many of today’s advanced electrical devices. For instance, due to their light weight, high-efficiency, and flexible architecture, multijunction III-V cells are attractive for use in weight-, space-, power-, or design-constrained systems like orbital technologies, unmanned aerial vehicles, electric vehicles, man- and vehicle-portable power systems, and even in concentrated photovoltaic devices where extreme physical space limitations may apply. Despite their many advantages, III-V multijunction cells remain relatively expensive and efforts are underway at NREL and elsewhere to both reduce cost or further improve efficiency to make III-V multijunction cells more affordable on a $/Watt basis.


Researchers at NREL have developed a technique that further enhances the absorption capabilities of III-V multijunction solar cells by combining two important elements in multijunction cells into a single layer.  The process involves the incorporation of the reflective quality of a distributed bragg reflector (DBR) into the metamorphic compositionally graded buffer layers (CGBs) that lie between lattice-mismatched sub-cell layers of a multijunction device.  The reflective qualities of the DBR enables increased light absorption in sub-cell layers above the metamorphic buffer and therefore enables the use of thinner, less expensive, and easier to deposit, absorber layers.  Moreover, the use of thinner absorber layers decreases the path length of radiation passing through the device, resulting in a significant boost to the end-of-life efficiency, particularly in AM0 applications where radiation hardness is of critical concern.

  • Improved radiation hardness
  • Increased carrier concentration
  • Photovoltaic conversion efficiency boosts
  • Cost savings through reduction in production materials
Applications and Industries
  • Aerospace
  • Aviation
  • Solar concentration applications
Technology Status
Technology IDDevelopment StageAvailabilityPublishedLast Updated
ROI 18-13PrototypeAvailable06/14/201806/14/2018

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To: Bill Hadley<>