INALAS AND INGAAS SOLAR CELL DEVELOPMENT FOR USE IN MONOLITHIC TRIPLE-JUNCTION SOLAR CELLS WITH IMPROVED SPECTRUM SPLITTING

A triple-junction cell based on a lattice constant of 5.816 Å using InAlAs - InGaAsP - InGaAs alloys can theoretically outperform those based on the GaAs lattice parameter by 3%. This lattice constant is close to that of InP but ultimately will require growth on a lower cost substrate such as GaAs or Si to have commercial impact. Here we present our progress on the essential sub-elements of this novel configuration, namely: (i) single-junction In0.52Al0.48As and In0.53Ga0.47As solar cells lattice matched to InP substrates with measured 1-Sun PV efficiencies of 13.8% and 9.3% respectively, (ii) a compositionally-graded InxGa1-xAs/InP metamorphic buffer layer (MBL) that alters the lattice constant from 5.65 Å (GaAs) to 5.87 Å (InP) and (iii) the growth of In0.52Al0.48As and In0.53Ga0.47As single junction cells on GaAs substrates.