AlGaAs top solar cell for mechanical attachment in a multi-junction tandem concentrator solar cell stack

Free-standing, transparent, tunables bandgap Al/sub x/Ga/sub 1-x/As top solar cells have been fabricated for mechanical attachment in a four-terminal tandem stack solar cell. The device has 1.8 eV top solar cells with efficiencies of 18% (100X, AM0), which would yield stack efficiencies of 31% (100X, AM0) with a silicon bottom cell. When fully developed, the Al/sub x/Ga/sub 1-x/As/Si mechanically stacked two-junction solar cell concentrator system can provide efficiencies of 36% (AM0, 100X). Liquid-phase epitaxy (LPE) growth techniques have been used. This is the first demonstration of a free-standing wide-bandgap top cell technology which can be readily developed for commercial availability based on the Al-Ga-As mixed-crystal system.<
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