Development and characterization of high-efficiency Ga/sub 0.5/In/sub 0.5/P/GaAs/Ge dual- and triple-junction solar cells

This paper describes recent progress in the characterization, analysis, and development of high-efficiency, radiation-resistant Ga/sub 0.5/In/sub 0.5/P/GaAs/Ge dual-junction (DJ) and triple-junction (TJ) solar cells. DJ cells have rapidly transitioned from the laboratory to full-scale (325 kW/year) production at Spectrolab. Performance data for over 470000 large-area (26.94 cm/sup 2/), thin (140 /spl mu/m) DJ solar cells grown on low-cost, high-strength Ge substrates are shown. Advances in next-generation triple-junction Ga/sub 0.5/In/sub 0.5/P/GaAs/Ge cells with an active Ge component cell are discussed, giving efficiencies up to 26.7% (21.65-cm/sup 2/ area), AM0, at 28/spl deg/C. Final-to-initial power ratios P/P/sub 0/ of 0.83 were measured for these n-on-p DJ and TJ cells after irradiation with 10/sup 15/ 1-MeV electrons/cm/sup 2/. Time-resolved photoluminescence measurements are applied to double heterostructures grown with semiconductor layers and interfaces relevant to these multijunction solar cells, to characterize surface and bulk recombination and guide further device improvements. Dual- and triple-junction Ga/sub 0.5/In/sub 0.5/P/GaAs/Ge cells are compared to competing space photovoltaic technologies, and found to offer 60-75% more end-of-life power than high-efficiency Si cells at a nominal array temperature of 60/spl deg/C.