High efficiency quadruple junction, four-terminal solar cells and modules by transfer printing

Conventional multi-junction (MJ) cells are limited by requirements in epitaxial growth and current-matching. Mechanically stacked MJ cells circumvent these disadvantages, but existing approaches lack scalable manufacturing processes and suitable interfaces between the stacked cells. Here we present materials and strategies designed to bypass these limitations. The schemes involve (1) printing of microscale solar cells, (2) advanced optical/electrical/thermal interface materials and (3) packaging techniques, electrical matching networks, and compact ultrahigh concentration optics. We demonstrate quadruple junction, four-terminal solar cells with measured efficiencies of 43.9% at concentrations exceeding 1000 suns, and modules with efficiencies of 36.5%.