Status of C3MJ+ and C4MJ Production Concentrator Solar Cells at Spectrolab

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.