Surface-activated-bonding-based InGaP-on-Si double-junction cells

InGaP-on-Si double-junction cells were fabricated by the surface activated bonding of InGaP-based top cell layers grown on GaAs substrates to Si-based bottom cells and the selective etching of GaAs substrates. The open-circuit voltage of the double-junction cells in the tandem operation was close to the sum of the open-circuit voltages of the top and bottom cells. The efficiency in the tandem operation of the n-on-p InGaP/(100)-Si double-junction cells was higher than the efficiencies of the respective subcells.