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Multijunction solar cells based on III-V semiconductors, having recently demonstrated 43.5%, remain the world's most efficient solar cells, and the preferred technology in point-focus and dense-array concentrator photovoltaic (CPV) system architectures. The year 2011 proved to be a pivotal year for CPV technology, with multiple power plant installations in the megawatt to tens of megawatt scale. Spectrolab is working closely with CPV system manufacturers to provide a reliable and well-characterized cell technology, in volumes commensurate with this increasing demand. The evolutionary C3MJ+ and the C4MJ cell technologies are the latest in a sequence of CPV solar cell designs, with conversion efficiencies approaching or greater than 40%. Both technologies have completed detailed characterization and qualification programs, including accelerated laboratory and (for C4MJ) on-sun reliability testing, and have entered into high volume production at Spectrolab's manufacturing facility in Sylmar, CA. The metamorphic C4MJ technology affords new opportunities to optimize cell designs, taking into consideration both the spectral optical transmittance of a particular CPV system and the installation site's average solar resource over a typical meteorological year.