Emerging classes of concentrator photovoltaic (CPV) modules reach efficiencies that are far greater than those of even the highest performance flat-plate PV technologies, with architectures that have the potential to provide the lowest cost of energy in locations with high direct normal irradiance (DNI). A disadvantage is their inability to effectively use diffuse sunlight, thereby constraining widespread geographic deployment and limiting performance even under the most favorable DNI conditions. This study introduces a module design that integrates capabilities in flat-plate PV directly with the most sophisticated CPV technologies, for capture of both direct and diffuse sunlight, thereby achieving efficiency in PV conversion of the global solar radiation. Specific examples of this scheme exploit commodity silicon (Si) cells integrated with two different CPV module designs, where they capture light that is not efficiently directed by the concentrator optics onto large-scale arrays of miniature multijunction (MJ) solar cells that use advanced III-V semiconductor technologies. In this CPV + scheme ("+" denotes the addition of diffuse collector), the Si and MJ cells operate independently on indirect and direct solar radiation, respectively. On-sun experimental studies of CPV + modules at latitudes of 35.9886°N (Durham, NC), 40.1125°N (Bondville, IL), and 38.9072°N (Washington, DC) show improvements in absolute module efficiencies of between 1.02% and 8.45% over values obtained using otherwise similar CPV modules, depending on weather conditions. These concepts have the potential to expand the geographic reach and improve the cost-effectiveness of the highest efficiency forms of PV power generation.photovoltaics | multijunction solar cells | concentration optics | diffuse light capture T he levelized cost of electricity (LCOE) is a primary metric that defines the economic competitiveness of photovoltaic (PV) approaches to electrical power generation (1). As the performance of the highest efficiency single-junction flat-plate PV modules begins to reach theoretical limits, research toward cost reductions in such technologies shifts from performance to topics related to materials utilization and manufacturing (2-5). By contrast, the efficiencies of multijunction (MJ) solar cells based on III-V compound semiconductors continue to improve steadily, at a rate of ∼1% per year over the last 15 y, due largely to progress in epitaxial growth processes, mechanical stacking techniques, and microassembly methods for adding junctions that further maximize light absorption and minimize carrier thermalization losses (6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20). Record MJ cell efficiencies now approach ∼46.0%, with realistic pathways to the 50% milestone (5). For economic deployment, however, the sophistication and associated costs of these cells demand the use of lenses, curved mirrors, or other forms of optics in conjunction with a mechanical tracker to geometrically concentrate incident direct sunlight in a manner tha...