Improved Multi Junction Solar Cell Technology for Satellites

Higher efficiency solar cells are needed to reduce mass, volume, and cost of DoD space missions. However, to achieve higher efficiency and radiation hardness of the best to date multi-junction photovoltaic (MJ PV) devices, several challenges must be addressed. This project aims to develop: 1) Quantum Well (QW)-based multi-junction cell technology that exhibits enhanced efficiency, and 2) Radiation-hardened PV cell design demonstrating the radiation tolerance of the QW multi-junction cell. Customized modeling tools will enable QW optimization, including: (a) geometrical ordering and variable QW size, (b) increased transport and separation of photogenerated carriers; and (c) improved electrical conductivity and enhanced collection efficiency. In Phase I, CFDRC, together with Rochester Institute of Technology, designed, fabricated and demonstrated the high-efficiency MQW concept for the middle cell in a multi-junction (InGaP/GaAs/Ge) configuration. We fabricated three MQW cell prototypes and performed characterization and testing, delivering a proof of feasibility. The design and implementation of QWs in this middle cell is directly applicable to a state-of-the-art lattice-matched cell and a metamorphic cell. Phase II will complete the development by implementing the high-efficiency MQW and radiation resistant middle cell within a multi-junction cell, resulting in significantly improved MJ QW solar cell performance under AM0 spectrum at the end of life. Device prototypes will be fabricated, demonstrated, and pre- and post-radiation characterization will be conducted. The developed technology will be suitable for insertion into the industrial manufacturing process for space solar cells. A solar panel prototype will also be assembled and demonstrated by testing.