III-V multijunction solar cells - from current space and terrestrial products to modern cell architectures

The standard Ga0.5In0.5P/Ga0.99In0.01As/Ge triple-junction (3J) solar cell is reaching its practical average efficiency limit of 30% for AM0 and 40% under concentration (xAM1.5d) as can be observed for AZUR's latest products for space application (3G30) and CPV (4C40). In addition, AZUR SPACE has developed dense array modules (ADAM) for dish concentrator application. Regarding modern cell architectures, recent progress by Fraunhofer ISE and AZUR SPACE is reported, including improved GaInNAs subcells for lattice-matched 4J and 6J solar cells, 3J MQW cells reaching 30% AM0 efficiency, continuous work on upright metamorphic 3J cells as well as processing of inverted cell structures. The paper gives a brief overview on these and other new concepts such as inverted metamorphic 3J and 4J cells and multi-junction solar cells based on semiconductor bonding.