GaAs/InGaAsN heterostructures for multi-junction solar cells

Solar-cell heterostructures based on GaAs/InGaAsN materials with an InAs/GaAsN superlattice, grown by molecular beam epitaxy, are studied. A $p$-GaAs/$i$-(InAs/GaAsN)/$n$-GaAs $p$–$i$–$n$ test solar cell with a 0.9-$\mu$m-thick InGaAsN layer has an open-circuit voltage of 0.4 V (1 sun, AM1.5G) and a quantum efficiency of $>$ 0.75 at a wavelength of 940 nm (at zero reflection loss), which corresponds to a short-circuit current of 26.58 mA/cm$^2$ (AM1.5G, 100 mW/cm$^2$). The high open-circuit voltage demonstrates that InGaAsN can be used as a material with a band gap of 1 eV in four-cascade solar cells.