Lattice-matched and metamorphic GaInP/GaInAs/Ge concentrator solar cells

Abstract

Recent developments in epitaxial III-V multijunction solar cell technology have allowed concentrator and 1-sun cells to reach new heights in efficiency under the terrestrial solar spectrum. The bandgaps of the GaInP and GaInAs subcells are controlled by varying indium content, up to 12% indium in the GaInAs middle cell, or 0.8% lattice mismatch. Shockley-Read-Hall recombination at dislocations in such metamorphic cells has been restricted to lower levels than previously achieved, and is compared to the lattice-matched case. Terrestrial GaInP/GaInAs/Ge 3-junction cells have been produced at Spectrolab with record efficiencies independently verified at NREL, of 31.3% for metamorphic 1-sun cells and 32.0% for lattice-matched 1-sun cells (25/spl deg/C, AM1.5G, 4.00 cm/sup 2/), and 35.2% for lattice-matched concentrator cells under the AM1.5 Direct, low-AOD spectrum (25/spl deg/C, 66 suns, 0.26 cm/sup 2/).