Development of a 1.0 eV (GaIn)(NAs) solar cell

(GaIn)(NAs) with a bandgap of 1.0 eV is an interesting material for the use in 4-junction solar cells in order to increase the efficiency under the AM0-spectrum. n-i-p- and p-i-n-homojunctions were grown in an AIX200 MOVPE reactor. Solar cells were fabricated using a technology normally applied to GaAs solar cells. An external quantum efficiency (EQE) of 30% was measured for the p-i-n-homojunctions. An improvement was found after annealing of the samples. The annealing step improves the quality of the p-doped emitter while no improvement was seen for the n-doped base material. The V/sub oc/ and I/sub sc/ values increase from /spl sim/370 mV to /spl sim/520 mV and /spl sim/9.8 mA/cm/sup 2/ to 15.6 mA/cm/sup 2/, respectively. However, the fill factor decreased down to 38% after the annealing. Changes in the growth process lead to maximum EQE values of over 60% resulting in a maximum efficiency of 4.3% for AM1.5 g.