Epitaxial GaAsP/Si Solar Cells with High Quantum Efficiency

We review recent progress in GaAsP/Si tandem cells and present a GaAsP/Si tandem cell with a high total short-circuit current density of 38.2 mA/cm
²
. Comparing the external quantum efficiency (EQE) of this tandem cell with benchmark perovskite/Si tandem cells reveals that at identical top cell bandgap, the GaAsP top cell exhibits higher or comparable EQE at all wavelengths, while the GaAsP-filtered Si bottom cell exhibits insufficient light trapping and parasitic absorption. Future improvement in the transparency of the GaAsyP
_1-y
graded buffer layer and the light trapping in the Si bottom cell promises GaAsP/Si tandem cells with a short circuit density above 20 mA/cm
²
.