Radiative cooling for low-bandgap photovoltaics under concentrated sunlight

Radiative cooling is a uniquely compact and passive cooling mechanism. Significant applications can be found in energy generation, particularly concentrating photovoltaics (CPV) and thermophotovoltaics (TPV). Both rely on low-bandgap PV cells that experience significant reductions in performance and lifetime when operating at elevated temperatures. This issue creates a significant barrier to widespread adoption. To address this challenge, we demonstrate enhanced radiative cooling for low-bandgap PV cells under concentrated sunlight for the first time. A composite material stack is used as the radiative cooler. Enhanced radiative cooling reduces operating temperatures by 10 °C, translating into a relative increase of 5.7% in open-circuit voltage and an estimated increase of 40% in lifetime at 13 suns. By using a model, we also estimate that the same setup could achieve an improvement of 34% in open-circuit voltage for 35 suns, which could reduce levelized costs of energy up to 33% for high-activation energy failure modes. The radiative cooling enhancement demonstrated here is a simple and straightforward approach, which can be generalized to other optoelectronic systems.