27.5% efficiency InGaP/InGaAs/Ge advanced triple junction (ATJ) space solar cells for high volume manufacturing

Results of improvements in Emcore\´s large-area ( a 26.6 cm²) triple-junction (3J) space solar cells are presented. Volume production of this InGaP/InGaAs/Ge advanced triple-junction (ATJ) process shows an individual cell average conversion efficiency of 27.5% (AMO, 135.3 mW/cm, 28°C) with observed lot average conversion efficiencies greater than 28.0%. The ATJ cells maintain a radiation hard design similar to that used in the first generation Emcore 3J solar cells. The power remaining factors after irradiation with 1-MeV electrons at fluences of 5E14, 1E15, and 5E15 e/ cm² are 0.89, 0.85,and 0.74 respectively. The realized improvements in the ATJ solar cell have resulted in part from an improved "blue" response in the Ge subcell, the addition of indium to the GaAs middle cell composition, and from improvements to the bulk material quality of the InGaP top cell.