25.5% efficient Ga0.35In0.65P/Ga0.83In0.17 as tandem solar cells grown on GaAs substrates

Theoretical calculations predict a higher power conversion efficiency for t he combination of Ga0.35In0.65P and Ga0.83In0.17As in a tandem solar cell, compared to the more commonly used Ga0.51In0.49P/GaAs approach. A record co nversion efficiency of 21.6% (AMI.5g) was recently achieved for a 1.18 eV G a0.83In0.17As solar cell, grown lattice-mismatched to the GaAs substrate ma terial. This paper reports on the device characteristics of first Ga0.35In0 .65P/Ga(0.65)In(0.17)AS tandem solar cells based on this very promising GaI nAs material. A high quantum efficiency, comparable to the lattice matched Ga0.51In0.49P on GaAs approach was achieved. A power conversion efficiency of 25.5% was measured under AM1.5d spectral conditions.