MONOLITHIC AND MECHANICAL MULTIJUNCTION SPACE SOLAR-CELLS

High-efficiency, lightweight, radiation-resistant solar cells are esse ntial to meet the large power requirements of future space missions. S ingle-junction cells are limited in efficiency. Higher cell efficienci es could be realized by developing multijunction, multibandgap solar c ells. Monolithic and mechanically stacked tandem solar cells surpassin g single-junction cell efficiencies have been fabricated. This article surveys the current status of monolithic and mechanically stacked mul tibandgap space solar cells, and outlines problems yet to be resolved. The monolithic and mechanically stacked cells each have their own pro blems related to size, processing, current and voltage matching, weigh t, and other factors. More information is needed on the effect of temp erature and radiation on the cell performance. Proper reference cells and full-spectrum range simulators are also needed to measure efficien cies correctly. Cost issues are not addressed, since two approaches ar e still in the developmental stage.