Photovoltaic efficiencies in lattice-matched III-V multijunction solar cells with unconventional lattice parameters

We explore the potential for high efficiency multijunction solar cells that are not lattice matched to currently available single crystal substrates, but are still formed of component subcells that can be lattice matched to one another in the III-V GaInAsP compound semiconductor material system. Using detailed balance calculations, the theoretical efficiency of three and four junction cells with lattice constants in the range from 5.65325 to 5.8687 Å are explored. In this range, a lattice-matched three junction cell with an In_xAl_1-xAs top subcell has a 56.2% detailed balance efficiency (500 suns). A lattice-matched four junction cell with 54.5% (500 suns) detailed balance efficiency is also identified.