Recent advances in multi-junction III–V solar cell development

Abstract This paper reviews recent progress at Varian to improve the efficiency of multijunction solar cells fabricated with GaAs-related materials. The most noteworthy achievement is the fabrication of a monolithic, two-terminal, two-junction AlGaAs/GaAs cell with a power conversion efficiency of 27.6% at 1 Sun, AM1.5 global. Recent results are presented for a number of single-junction and multijunction monolithic cell structures fabricated with the AlGaAs/GaAs/InGaAs materials system grown by metal-organic chemical vapor deposition. The progress and problems for lattice-matched and lattice-mismatched structures and cell interconnects are discussed and assessed. The latest results are significant steps toward demonstration of the viability of two- and three-junction cascade cells. The hurdles to be overcome in achieving efficiencies above 30% for 1 Sun and concentrator cells are discussed.