GaAs/silicon PVMirror tandem photovoltaic mini-module with 29.6% efficiency with respect to the outdoor global irradiance

Balance-of-system costs now dominate the installed cost of photovoltaic systems, causing the annually averaged module efficiency to become a primary system cost driver. The resulting continued push towards higher module efficiencies, coupled with the dominance of single-axis tracking in the utility-scale PV market, may create an opportunity for a low-concentration tandem module technology. Here, we demonstrate such a tandem, using the “PVMirror” concept, on the mini-module scale. The tandem couples a (concentrating) silicon PVMirror having an aperture area of 156.25 cm² with a gallium arsenide receiver to achieve 29.6% efficiency with respect to the outdoor global irradiance. Unlike most concentrating technologies, the silicon PVMirror collects some of the diffuse light, but the tandem would nevertheless achieve 31% efficiency in the absence of diffuse light, as in a laboratory measurement. The same tandem technology can be implemented with a wide-bandgap thin-film PVMirror and silicon receiver—a potentially cost-competitive combination—when efficient wide-bandgap cells have been developed.