8% space and 38.8% terrestrial 5J direct bonded cells

Spectrolab has fabricated a direct semiconductor bonded space solar cell with an efficiency of 35.8% under the AM0 space spectrum. Using a similar technology, Spectrolab has achieved a 5-junction (5J) direct bonded terrestrial cell with a record efficiency of 38.8% under the one-sun AM1.5G terrestrial spectrum. Efforts to further improve the 5J cell efficiency have focused on development of the top 3 junctions (T3J) grown on GaAs. Experiments with top 3J isotype cells have yielded an improvement of 1% in current and 100 mV in voltage for the T3J. Spectrolab has also made significant improvements in its direct bonding process. The improved process has increased bond strengths by more than a factor of 5 and eliminated issues with large voids.