Lightweight tandem GaAs/CuInSe/sub 2/ solar cells

High-efficiency, ultralightweight, mechanically stacked 4-cm/sup 2/ thin-film tandem solar cells are discussed. The tandem stack consists of a single-crystal, thin-film Ga(Al)As cell fabricated by the cleavage of lateral epitaxy for transfer (CLEFT) process and adhesively bonded to the top of a CdZnS/CuInSe/sub 2/ polycrystalline thin-film cell deposited on glass. Maximum tandem efficiency in a four-terminal configuration of 21.6% AM0 have been demonstrated. This represents the highest thin-film cell efficiency reported to date. Individual subcells with efficiencies of 19.5% for CLEFT GaAs and 3.0% for CuInSe/sub 2/ have also been achieved. Cell specific power as high as 600 W/kg has been achieved with a 4-cm/sup 2/ cell weight of 188 mg without coverglass, at an efficiency of 20.8% AM0.<
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