GaAsP solar cells on GaP substrates by molecular beam epitaxy

We demonstrate molecular beam epitaxy (MBE) of GaAsxP1−x/GaP solar cells over a range of bandgap energies (Eg). Identical GaAs0.66P0.34 cells on GaAs and GaP exhibit similar properties; GaAs0.66P0.34/GaP cells with Eg = 1.82 eV produced an open-circuit voltage (Voc) of 1.24 V, ∼40 mV lower than previous GaAs0.66P0.34/GaAs cells. We then grew GaAs0.56P0.44/GaP cells with Eg = 1.92 eV to investigate their suitability for wide-Eg applications, reaching Voc = 1.27 V. For potential dual-junction integration on Si, we grew Eg = 1.71 eV GaAs0.73P0.27/GaP cells, attaining Voc = 1.15 V. These results indicate that GaAsxP1−x/GaP solar cells by MBE are promising for integration onto Si and for other photovoltaic applications.