Fabrication and numerical analysis of AlGaAs/GaAs tandem solar cells with tunnel interconnections

High-efficiency (20.2% at 1 sun, AM 1.5) Al/sub 0.4/Ga/sub 0.6/As/GaAs tandem solar cells are successfully fabricated by molecular-beam epitaxy. The interconnection between the AlGaAs top cell and the GaAs bottom cell consists of a GaAs tunnel junction sandwiched between AlGaAs layers and provides a high-quality tunnel junction. Numerical analysis suggests that an efficiency of 30% can be realized by increasing the carrier lifetimes of AlGaAs layers to 10/sup -8/ s. An efficiency of 35% is expected to be obtainable by replacing the GaAs tunnel junction with an Al/sub 0.33/Ga/sub 0.67/As tunnel junction.<
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