The U.S. Department of Energy’s (DOE) National Renewable Energy Laboratory (NREL) has granted MicroLink Devices of Chicago, Illinois USA, an exclusive license to produce and sell NREL’s inverted metamorphic multi-junction (IMM) solar cell technology. The IMM solar cell structure allows the fabrication of solar cells with very high efficiency as well as low weight, which are ideal traits for solar cells that power satellites and solar aircraft.
Multi-junction solar cells, which are the World’s most efficient, use multiple light-absorbing layers to transform different wavelength ranges of the solar spectrum into electricity. However, multi-junction solar cells with germanium substrates have historically been employed exclusively in high-performance satellites. On the other hand, a solar cell with an IMM design integrates an optimum combination of three or more compound semiconductor materials for improved efficiency.
Production of IMM multi-junction solar cells requires the deposition of thin layers of a semiconductor on a substrate such as gallium arsenide (GaAs). Then, the addition of a metamorphic buffer layer permits the growth of junction materials with perfect bandgaps for efficient energy conversion such as indium gallium arsenide (InGaAs). Because of the buffer layer, such junction materials do not have to be lattice-matched to the GaAs substrate.
Using an IMM solar cell design, MicroLink Devices has demonstrated an efficiency of 32.3% under 1-sun AM0.
MicroLink notes that these IMM solar cells are can be fabricated with the company’s proprietary epitaxial lift-off (ELO) technology. The firm has been developing this ELO for the past ten years with funding from numerous US agencies including DARPA, NASA, the Air Force Research Laboratory, the Office of Naval Research, NAVAIR, the Army Research Office, the Army REF, CERDEC, and the Department of Energy.
“We are excited to be manufacturing solar cells and arrays using NREL’s IMM technology that have industry-leading performance as well as cost,” said Dr. Noren Pan, president and CEO of MicroLink Devices.