Plasmon-Enhanced Infrared Emission Approaching the Theoretical Limit of Radiative Cooling Ability

Radiative cooling, a passive cooling technique, has shown great potentials in recent years to lower the power consumption of air conditioning. With the ever-increasing cooling power being reported, the theoretical cooling limit of such a technique is still unclear. In this work, we proposed a theoretical limit imposing an upper bound for the attainable cooling power. To approach this limit, we exploited the localized surface plasmon resonance (LSPR) of self-doped In₂O₃ nanoparticles, which enhance the emissivity in both primary and secondary atmospheric windows. The measured cooling power of poly(methyl methacrylate) (PMMA) films containing 4.5% In₂O₃ nanoparticles is very close to the limit with the closest value only about 0.4 W/m² below the limit. Hopefully, this work may help the researchers better evaluating the performance of their device in the future and pave the way for achieving even higher radiative cooling powers during the daytime operations with the help of LSPR.