25.5% efficient Ga/sub 0.35/In/sub 0.65/P/Ga/sub 0.83/In/sub 0.17/As tandem solar cells grown on GaAs substrates

Theoretical calculations predict a higher power conversion efficiency for the combination of Ga/sub 0.35/In/sub 0.65/P and Ga/sub 0.83/In/sub 0.17/As in a tandem solar cell, compared to the more commonly used Ga/sub 0.51/In/sub 0.49/P/GaAs approach. A record conversion efficiency of 21.6% (AM1.5 g) was recently achieved for a 1.18 eV Ga/sub 0.83/In/sub 0.17/As solar cell, grown lattice-mismatched to the GaAs substrate material. This paper reports on the device characteristics of first Ga/sub 0.35/In/sub 0.65/P/Ga/sub 0.83/In/sub 0.17/As tandem solar cells based on this very promising GaInAs material. A high quantum efficiency, comparable to the lattice-matched Ga/sub 0.51/In/sub 0.49/P on GaAs approach was achieved. A power conversion efficiency of 25.5% was measured under AM1.5d spectral conditions.