Lightweight, low cost GaAs solar cells on 4″ epitaxial liftoff (ELO) wafers

GaAs single junction solar cells were fabricated on epitaxial liftoff (ELO) 4:″ GaAs wafers. 1 cm² single junction GaAs solar cells have been fabricated with a yield ≫80% across full 4″ ELO wafers. Photoluminescence studies of ELO GaAs wafers showed no evidence of residual strain in the layers as indicated by single peak at 870 nm at 300 K. Transmission electron microscopy studies of ELO solar cells indicated no evidence of threading dislocations, voids or delaminating at the semiconductor-metal interface. Quantum efficiency measurements on ELO GaAs single junction solar cells indicated improved performance near the band edge in the ELO samples compared with conventional, non-ELO GaAs cells. GaAs ELO solar cells exhibited efficiencies in excess of 21% with Voc = 1.007 V and FF≫85%.