MicroLink Devices of Niles, IL, USA has entered into an exclusive license agreement with the US Department of Energy’s (DOE) National Renewable Energy Laboratory (NREL) to commercialize inverted metamorphic multi-junction (IMM) solar cell technology. The IMM solar cell architecture enables the manufacture of solar cells with very high efficiency as well as light weight, which are ideal for powering satellites and solar aircraft.
As the most efficient solar cells, multi-junction solar cells based on germanium substrates have historically been used exclusively in very high-performance satellite applications. The IMM design is an innovative approach to further improve efficiency by integrating an optimum combination of three or more compound semiconductor materials. IMM multi-junction solar cells are manufactured by depositing thin layers of semiconductor on a substrate such as gallium arsenide (GaAs). A metamorphic buffer layer enables the growth of junction materials with optimum bandgaps for energy conversion, such as indium gallium arsenide (InGaAs), that are not lattice-matched to the GaAs substrate. MicroLink has demonstrated an efficiency of 32.3% under 1-sun AM0 using an IMM design.
IMM solar cells are synergistic with MicroLink’s proprietary epitaxial lift-off (ELO) technology, which has been under development for the past ten years. Using the ELO process, MicroLink can peel off thin layers of active solar cell material that were deposited on the GaAs substrate. Removing the substrate enables the fabrication of solar cells with exceptional light weight and specific powers greater than 3000W/kg. The substrate can also be used multiple times to lower manufacturing costs. The development of MicroLink’s ELO technology was sponsored by numerous US agencies including NASA, DARPA, the Air Force Research Laboratory, the Office of Naval Research, NAVAIR, Army Research Office, Army REF, CERDEC, and the DOE.
“We have been working for more than a decade on the scale-up and manufacturing of this design, which enables us to provide very compelling solar solutions for powering high-altitude long-endurance (HALE) aircraft and space satellites,” says MicroLink’s president & CEO Dr Noren Pan.
MicroLink has previously announced a production contract to provide ELO multi-junction solar sheets to Airbus Defence and Space for use on the Zephyr S HALE platform. The Zephyr is a new class of unmanned air vehicle (UAV) that operates as a high-altitude pseudo-satellite (HAPS), enabling affordable, persistent, local satellite-like services. The aircraft runs exclusively on solar power, and the Zephyr aircraft is at the forefront of the HAPS arena, holding world records with regards to absolute endurance (more than 14 days) and altitude (more than 70,000 feet).