Ultra-High-Efficiency, Multi-Junction Solar Cells for Space Applications

ABSTRACT: The innovation in this proposed Phase I SBIR program is the development of a new type of top subcell for a novel, all-lattice-matched multijunction solar cell. The proposed structure will achieve a much higher end-of-life power conversion efficiency, in conjunction with a greatly increased power density, than current state-of-the-art photovoltaic technologies. Photovoltaic power sources for satellite applications must be high-efficiency, lightweight, and radiation-hard. MicroLink proposes to meet these criteria with an innovative, high-efficiency triple-junction solar cell lattice-matched to InP. The proposed cell comprises an InAlAsSb top subcell (1.80 eV), an InGaAlAs or GaAsP middle subcell (1.17 eV) and an InGaAs bottom subcell containing InGaAs quantum well layers (0.71 eV). The InAlAsSb subcell will be developed in the proposed program. With this multijunction bandgap combination, AM0 power conversion efficiencies greater than 40% should be achievable. MicroLink"s epitaxial lift-off process will be used to remove the substrate to produce ultra-lightweight, flexible, robust solar cells. Substrate reuse will render this InP-based approach cost-effective. BENEFIT: In addition to their application in satellites, high efficiency, lightweight solar cells are needed for many portable applications. The ability to quickly recharge the batteries of portable devices is highly attractive in areas where electricity has limited availability. As the cost of solar cells continues to decrease, novel consumer applications will be realized. The market potential is very large due to the increasing demand for portable electronic devices, such as smart phones and laptop computers.