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Progress toward the development of dual junction GaAs/Ge solar cellsLarge area GaAs/Ge cells offer substantial promise for increasing the power output from existing silicon solar array designs and for providing an enabled technology for missions hitherto impossible using silicon. Single junction GaAs/Ge cells offer substantial advantages in both size, weight, and cost compared to GaAs cells but the efficiency is limited to approximately 19.2 to 20 percent AMO. The thermal absorptance of GaAs/Ge cells is also worse than GaAs/GaAs cells (0.88 vs 0.81 typ.) due to the absorption in the Ge substrate. On the other hand dual junction GaAs/Ge cells offer efficiencies up to ultimately 24 percent AMO in sizes up to 8 x 8 cm but there are still technological issues remaining to achieve current matching in the GaAs and Ge cells. This can be achieved through tuned antireflection (AR) coatings, improved quality of the GaAs growth, improved quality Ge wafers and the use of a Back Surface Field (BSF)/Back Surface Reflector (BSR) in the Ge cell. Although the temperature coefficients of efficiency and voltage are higher for dual junction GaAs/Ge cells, it has been shown elsewhere that for typical 28 C cell efficiencies of 22 percent (dual junction) vs 18.5 percent (single junction) there is a positive power tradeoff up to temperatures as high as 120 C. Due to the potential ease of fabrication of GaAs/Ge dual junction cells there is likely to be only a small cost differential compared to single junction cells.
Document ID
19910009871
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Lillington, D. R. (Spectrolab, Inc., Sylmar CA., United States)
Krut, D. D. (Spectrolab, Inc., Sylmar CA., United States)
Cavicchi, B. T. (Spectrolab, Inc., Sylmar CA., United States)
Ralph, E. (Hughes Aircraft Co. Los Angeles, CA., United States)
Chung, M. (Air Force Wright Aeronautical Labs. Wright-Patterson AFB, OH., United States)
Date Acquired
September 6, 2013
Publication Date
January 1, 1991
Publication Information
Publication: NASA, Lewis Research Center, Space Photovoltaic Research and Technology, 1989
Subject Category
Energy Production And Conversion
Accession Number
91N19184
Funding Number(s)
CONTRACT_GRANT: F33615-89-C-2900
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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