1.73 eV AlGaAs/InGaP heterojunction solar cell grown by MBE with 18.7% efficiency

We report on AlGaAs-based heterojunction solar cells grown by solid source molecular beam epitaxy (MBE). We investigate InGaP and AlGaAs material quality and we demonstrate significant efficiency improvements by combining the best of each alloy: a thick p-AlGaAs base with tunable bandgap, and a thin 50 nm n-InGaP emitter separated by a thin intrinsic AlGaAs layer. We report a certified solar cell conversion efficiency of 18.7% with a 2-mu m-thick AlGaAs layer and a bandgap of 1.73 eV, suitable for high efficiency Si-based tandem devices.