High specific power (AlGaAs)GaAs/CuInSe/sub 2/ tandem junction solar cells for space applications

The authors report the fabrication of a high-efficiency, lightweight GaAs/CuInSe/sub 2/ tandem cell on a 2-mil-thick substrate, update 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/ GaAs/CuInSe/sub 2/ tandem cells has improved to 21.6% AM0. This is the highest efficiency ever reported for a thin-film photovoltaic cell. Among the tandem cells fabricated, the efficiencies of the best individual GaAs and CuInSe/sub 2/ subcells were 19.5% and 3.0%, respectively. 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. The effects of radiation and operating temperature on GaAs/CuInSe/sub 2/ tandem cells is also discussed, and an interconnect scheme for forming a voltage-matched circuit of three GaAs cells in parallel and three CuInSe/sub 2/ cells in series is proposed. >