GaInNAs solar cell with back surface reflector

We report the effects of back surface reflectors on quantum efficiency of single-junction 1 eV GaInNAs solar cells. For solar cells with Au back surface reflector, an average external quantum efficiency of 72% was achieved between 920 nm and 1250 nm. The average internal quantum efficiency of the cell was over 90% for the same wavelength range. The highest short-circuit current density calculated from the external quantum efficiency of a solar cell with Au back surface reflector was 12.8 mA/cm2, which is 17% higher than what was obtained using conventional Ti/Au metallization. This would enable fabrication of GaInP/GaAs/GaInNAs solar cell with an efficiency of at least 30% at AM1.5G.