High-Efficiency, Radiation-Hard Double Epitaxial Lift-Off Multi-Junction Solar Cell

ABSTRACT:MicroLink Devices, in collaboration with Dr. Scott Messenger at the University of Maryland Baltimore County (UMBC), proposes to develop an ultra-high efficiency, radiation-hard, six-junction solar cell for application to Air Force space missions. The proposed technology will comprise lattice-matched subcells grown on InP and GaAs substrates that are mechanically attached in a monolithic structure to achieve an AM0 efficiency in excess of 40%. To render the solar cell cost-efficient, epitaxial lift-off (ELO) will be used to separate the epitaxial layers from the InP substrate, allowing it to be reused for multiple growth cycles. The thin epitaxial layers will be attached to the back of the GaAs substrate in the final device structure using an epoxy bonding process. Dr. Messenger, a pioneer in the field of radiation modeling, will perform realistic environment simulations for missions in GEO, MEO and LEO, and the solar cell structure will be optimized for performance in the relevant mission radiation environment.BENEFIT:A successful development program will result in an increase in the efficiency of our multi-junction solar cells. The expected absolute efficiency of the devices ultimately enabled by the proposed technology is at least 40%. The proposed high-efficiency solar cells will be an attractive replacement for existing Ge-based triple-junction solar cells in all applications in which these cells are used. A major potential application is high-efficiency solar cells for use in solar-powered spacecraft, which will meet the needs of NASA, the DoD, other Federal Agencies, and the private sector. Customers of the products would be the makers of solar arrays for spacecraft, including Boeing, Lockheed Martin, ATK, and Space Systems Loral. Other applications that would benefit from increased efficiency solar cells include high-altitude, long-endurance (HALE) solar-powered aircraft. These aircraft are attractive for remote surveillance applications in which the aircraft could remain on station for months or years. In order to increase the geographic area that the HALE aircraft can cover, it is essential that the efficiency of the solar cell be improved. The cells described in the proposal could be easily converted for use in HALE applications. Customers that could benefit from this cell technology include DARPA (Vulture aircraft), Airbus (manufacturer of the Zephyr UAV), and Facebook or Google (new players in the HALE market).