Growing interest in renewable energy combined with the excellent performance of compound-semiconductor solar cells inspires a vision of large-scale deployment of solar systems using these cells. Three-junction, GaInP/Ga(In)As/Ge solar cells have demonstrated an efficiency of 39%. Many companies are developing solar concentrator systems based on these commercially available cells. This paper reviews compound-semiconductor solar-cell technology from the viewpoint of researchers experienced with metal organic vapor-phase epitaxy (MOVPE) growth of other compound-semiconductor devices. We describe the generic structure of today's multijunction solar cells and some of the challenges of implementing these structures. Several new device structures are currently being investigated toward achieving efficiencies above 40%. The potential for growth of this technology is huge, because high-efficiency (multijunction) concentrator systems have a chance to capture a significant part of the large-scale electricity photovoltaic market. (c) 2006 Elsevier B.V. All rights reserved.