Wide spectral coverage (0.7–2.2 eV) lattice‐matched multijunction solar cells based on AlGaInP, AlGaAs and GaInNAsSb materials

Abstract

AbstractWe report on the progress in developing lattice‐matched GaAs‐based solar cells with focus on developing AlGaInP, AlGaAs, and GaInNAsSb materials, aiming at achieving a wide spectral coverage, that is, 0.7–2.2 eV. To this end, we first benchmark the performance of an upright four‐junction GaInP/GaAs/GaInNAsSb/GaInNAsSb solar cells grown by molecular beam epitaxy on p‐GaAs substrates with bandgaps of 1.88, 1.42, 1.17, and 0.93 eV, respectively. The four‐junction cell exhibited an efficiency of ~39% at 560‐sun illumination while showing good electrical performance even up to 1000 suns. As a first step to further improve the efficiency toward 50% level, we demonstrate AlGaInP (>2 eV) and GaInNAsSb (<0.8 eV) subcells. We prove that AlGaInP cells with 0.1 Al composition would exhibit current‐matching condition when being incorporated in a five‐junction architecture together with two GaInNAsSb bottom and AlGaAs top junctions. Furthermore, current matching required for a six‐junction tandem architecture is achieved for an Al composition of 0.26. Overall, the results open a practical path toward fabrication of lattice‐matched solar cells with more than four junctions.