Lightweight (AlGaAs)GaAs/CuInSe/sub 2/ tandem junction solar cells for space applications

Mechanically stacked tandem cells consisting of GaAs thin-film upper cells and CuInSe/sub 2/ thin-film lower cells have been developed to meet the increasing power needs projected for future spacecraft. The authors report the fabrication of the first highly efficient lightweight GaAs/CuInSe/sub 2/ tandem cell on a 2-mil thick substrate, update recent performance improvements in thin-film GaAs/CuInSe/sub 2/ tandem cells, and discuss their application to space power systems. The efficiency of 4-cm/sup 2/ cells has improved to 21.6% AM0, the highest ever reported for a thin-film photovoltaic cell. Lightweight 4-cm/sup 2/ tandem cells have been successfully fabricated with efficiencies as high as 20.8%. These cells weighed about 180 mg without optimized substrate trimming. Radiation and operating temperature effects on GaAs/CuInSe/sub 2/ tandem cells are also discussed, and an interconnect scheme to form a voltage-matched string is described.<
>