High-efficiency GaInP/GaAs/InGaAs triple-junction solar cells grown inverted with a metamorphic bottom junction

The authors demonstrate a thin, Ge-free III-V semiconductor triple-junction solar cell device structure that achieved 33.8%, 30.6%, and 38.9% efficiencies under the standard 1 sun global spectrum, space spectrum, and concentrated direct spectrum at 81 suns, respectively. The device consists of 1.8 eV Ga0.5In0.5P, 1.4 eV GaAs, and 1.0 eV In0.3Ga0.7As p-n junctions grown monolithically in an inverted configuration on GaAs substrates by organometallic vapor phase epitaxy. The lattice-mismatched In0.3Ga0.7As junction was grown last on a graded GaxIn1-xP buffer. The substrate was removed after the structure was mounted to a structural handle. The current-matched, series-connected junctions produced a total open-circuit voltage over 2.95 V at 1 sun. (C) 2007 American Institute of Physics.