Monolithic two-junction AlGaAs/GaAs solar cells

Abstract

Monolithic two-junction two-terminal AlGaAs/GaAs solar cells were grown during two-stage liquid phase epitaxy. At the first stage the GaAs-based bottom subcell with a tunnel junction was grown on n-GaAs(Sn) substrate. Test samples of such a cell without layers of the tunnel junction and with thin enough p-Al/sub 0.9/Ga/sub 0.1/As window layer demonstrated the efficiencies of 27.5% (AM1.5D, 140 Suns) and of about 25% (AM1.5D, 1000-1500 Suns). At the second stage, the top AlGaAs subcell was grown. The following parameters have been measured in tandems: V/sub OC/=2.53 V, FF=0.80 at 50 Suns (AM0). An efficiency of 20.3% (AM0) has been achieved.