GaAs/Ge tandem-cell space concentrator development

• Published in: IEEE transactions on electron devices Vol. 37; no. 2; pp. 455 - 463
• Main Authors: Wojtczuk, S.J., Tobin, S.P., Keavney, C.J., Bajgar, C., Sanfacon, M.M., Geoffroy, L.M., Dixon, T.M., Vernon, S.M., Scofield, J.D., Ruby, D.S.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01-02-1990; Institute of Electrical and Electronics Engineers
• Subjects: Applied sciences; Energy; Exact sciences and technology; Gallium arsenide; Low earth orbit satellites; Natural energy; Optical filters; P-n junctions; Photonic band gap; Solar energy; Solar power generation; Solar thermal conversion; Space technology; Substrates; Sun; Test equipment; Space application; Solar cell; Gallium Arsenides; Voltage current curve; Manufacturing process; Germanium; Performance; Structure; Tandem mount; Optimization
• ISSN: 0018-9383; 1557-9646
• DOI: 10.1109/16.46383

GaAs/Ge monolithic tandem two-junction concentrators are being developed by optimizing separate one-junction GaAs and Ge cells that simulate the GaAs top cell and Ge bottom cell of the tandem. Separation allows easier analysis of the tandem's top and bottom cells than if these two junctions were in series. The best GaAs top cell has an independently measured AM1.5D efficiency of 28.7% at 200 suns and 25 degrees C (24.5% AM0 at 170 suns), a record for a monolithic cell without a prismatic cover. The Ge bottom cells have a GaAs optical filter (but no GaAs junction) to replicate the spectrum that the Ge cell sees when incorporated into a tandem. The best Ge-under-GaAs bottom cell efficiency is 4.6% AM0 at 103 suns. Evidence that the 900-1800-nm response seen from the Ge bottom cell is due to a p-n junction in the Ge and not a GaAs/Ge heterojunction is presented.< >