NSTI Nanotech 2009

Multi-quantum well multi-junction space solar cells

A. Freundlich, A. Alemu
University of Houston, US

Keywords: multi-quantum well, III-V, multi-junction, space, solar cell

Abstract:

Standard InGaP-GaAs-Ge cell is modified by incorporating pseudomorphic multi-quantum wells (MQW) of InGaAs to increase the photocurrent of the limiting GaAs subcell. The approach as demonstrated here enables the multi-junction tandem device to be made with all sub-cells optimized, rather than with a deliberately degraded top cell, as is now the case. A modeling of the performance of the proposed device indicates possibilities for achieving practical efficiencies in excess of 35 percent under typical space sunlight illumination (almost 20% above the present art). The current/voltage and spectral quantum efficiency characteristics of GaAs MQW solar cells grown by chemical beam epitaxy are found to be consistent with model predictions, showing both an increase of the cell operating wavelength range and a superior current output. The device is predicted as being capable to achieve end of life efficiency of about 30 percent at radiation doses equivalent of 10 years operation in Geo-stationary orbits (1 MeV electron radiation fluences in excess of 10^15cm^2). The projected radiation tolerance of the proposed device exceed significantly those of the existing conventional space solar cell technologies, making it particularly suitable for use in long duration space missions.
 
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