40.8% efficient inverted triple-junction solar cell with two independently metamorphic junctions

A photovoltaic conversion efficiency of 40.8% at 326 suns concentration is demonstrated in a monolithically grown, triple-junction III–V solar cell structure in which each active junction is composed of an alloy with a different lattice constant chosen to maximize the theoretical efficiency. The semiconductor structure was grown by organometallic vapor phase epitaxy in an inverted configuration with a 1.83 eV Ga.51In.49P top junction lattice-matched to the GaAs substrate, a metamorphic 1.34 eV In.04Ga.96As middle junction, and a metamorphic 0.89 eV In.37Ga.63As bottom junction. The two metamorphic junctions contained approximately 1×105 cm−2 and 2–3×106 cm−2 threading dislocations, respectively.