III-V compounds for solar cell applications

Research activities in the field of III-V solar cells are reviewed. III-V c ompound semiconductors are used for space solar cells, concentrator solar c ells, and in thermophotovoltaic generators. The epitaxial growth of ternary and quaternary material by MOVPE and LPE allows us to realize various band gaps. Multi-junction solar cells with different band gaps are necessary to obtain efficiencies larger than 30%. Recent results of the III-V solar cel l research at the Fraunhofer ISE are presented. A mechanically stacked GaAs /GaSb tandem concentrator solar cell achieved an efficiency of 31.1% under 100 x AM1.5d. An efficiency of 23% for a two-terminal concentrator module ( 486 cm(2)) with Fresnel lenses has been measured under realistic outdoor co nditions.