Lattice-matched multijunction solar cells employing a 1 eV GaInNAsSb bottom cell

Over the past 15 years, tremendous effort has been put forth into increasing the efficiency of multijunction solar cells used in concentrator photovoltaics (CPV) systems. Because the cell represents a small portion of the total CPV system cost, modest improvements in cell efficiencies have a large impact on reducing the levelized cost of electricity. To address the need for higher efficiency CPV cells, Solar Junction is currently manufacturing a lattice-matched multijunction solar cell that employs a 1 eV GaInNAsSb bottom subcell in lieu of the traditional Ge subcell. Our standard 5.5 mm(2) product has recently achieved a world record in power conversion efficiency. In this article, we report on the design, performance, and integration of this high-performance cell. The importance of overdriving the GaInNAsSb bottom subcell is discussed in addition to the optimization of the anti-reflection coating used for cells under glass secondary optics. (C) 2012 Society of Photo-Optical Instrumentation Engineers (SPIE). [DOI: 10.1117/1.JPE.2.021805]