21% (one sun, air mass zero) 4 cm2 GaAs space solar cells

Abstract
GaAs space solar cells with areas of 4 cm2 have been fabricated by metalorganic chemical vapor deposition. The AlGaAs‐GaAs heteroface structures have been grown in both the pn and np configurations. Under one sun, air mass zero conditions and at 25 °C, the pn cell is characterized by a short‐circuit current density of 32.3 mA/cm2, an open‐circuit voltage of 1.05 V, and a fill factor of 0.84, resulting in a conversion efficiency of 21.1%. The corresponding values for np cells are 33.8 mA/cm2, 1.01 V, and 0.83, resulting in a conversion efficiency of 21.0%.