High Efficiency Floating Junction GaAs Solar Cell for Space Applications. Phase 1.

AstroPower has demonstrated the feasibility of a lightweight, high efficiency GaAs solar cell that will have superior performance characteristics compared to conventional GaAs solar cells in the space environment. The solar cell design consists of a front floating junction that is coupled to a back collecting junction through the injection of minority carriers across a thin base. Performance benefits are enabled by incorporating an all back contact design with the electrostatic bonding technique and the use of multiple active junctions. By using the proper geometrical and electrical considerations, losses associated with grid shading and low energy radiation damage will be minimized. The key results of the Phase I program include demonstration of an 11 efficient AMO, 1X, 1 sq cm floating junction GaAs solar cell and a 3 micrometers thick GaAs layer electrostatically bonded to high temperature glass capable of surviving process temperatures up to 700 deg C. This ensures stability of the laminate throughout the process sequence and enables numerous potential applications for thin GaAs semiconductor devices. Continuation of process development in Phase II is anticipated to produce, when fully optimized, a radiation resistant solar cell which has been modeled to have an efficiency of 21.9.