Fabrication of high efficiency, III-V multi-junction solar cells for space concentrators

High-efficiency multijunction cells have been fabricated for use in space concentrator modules at concentrations of 8-15 suns. Modeling and optimization efforts to modify Spectrolab's 1-sun cells for use at concentration are described. An experimental population of 200 cells of 3.5 cm/sup 2/ aperture area (4.2 cm/sup 2/ total area) grown using a variety of conditions had an average efficiency of 29.6% at 8 suns AMO. This population included several cells which exceeded 31% aperture area efficiency and 32% active area efficiency. A Spectrolab cell was measured in ENTECH's mini-concentrator module (at approximately 8 suns) with a combined lens/cell mini-module efficiency of 30.8% under outdoor sunlight, which-is, to our knowledge, the first time the 30% barrier has been broken for such a module.