30% Efficient Three Junction Solar Cells for Space Concentrator Modules

摘要

The benefits of mechanically stacked tandem concentrator solar cells were first demonstrated on a NASA mission in 1994. In that case, transparent GaAs cells were stacked on top of infrared-sensitive GaSb booster cells and arrayed in a point-focus solar concentrator module. The results were high efficiency, excellent radiation resistance and high voltage tolerance, all of which sustained some interest in concentrator arrays. Since then, the lens design has evolved to a linear geometry used with high efficiency non- transparent GaInP2/GaAs cells on germanium substrates. These high bandgap dual junction cells still leave about 35% of the sun's longer wavelength energy uncollected. The proposal for this contract was to make the dual junction cell transparent to that long wavelength range and stack it on a GaSb booster cell for added efficiency gains. Tecstar made the transparent dual junction GaInP2/ GaAs cells on GaAs substrates as a subcontractor, and JX Crystals took on the tasks of booster cell fabrication as well as assembly and testing for this Phase I effort. Resulting dual junction cells achieved efficiencies of 29.6% at a 15 sun concentration level.