Dynamically Synergistic Solar and Mid-Infrared All-Season Radiative Thermoregulation Based on Reversible Metal Electrodeposition

The coldness of the deep universe and the hotness of the sun have been considered renewable thermodynamic resources for sustainable thermoregulation. How to utilize both resources showed drastic improvement in the past decade, enabled by the plasmonic and nanophotonic research. Remarkably, the rational photonic and thermal design has pushed forward the power and efficiency of daytime radiative cooling. In this presentation, we will introduce our recent research progress on electrochemical devices that can electrically switch between solar heating and radiative cooling states, by reversibly electrodepositing metal on graphene. Such a non-trivial and opposite spectral tuning requires the fabrication of the ultra-wideband transparent conductive electrode, which is transparent in both solar and mid-IR regimes, and the precise control of the plasmonic nanoparticles’ morphology during the reversible metal electrodeposition. With the optimization of every device component, this device can maximize its solar reflectivity at the cooling state and minimize its thermal emissivity at the heating state, and thus can serve as the smart building envelope for year-round HVAC energy saving. Ideally, the device can help buildings save 19.2% of HVAC energy across the United States, based on the building energy simulation results. The durable electrodeposition and broad-band spectral tuning are confirmed by the DFT simulations and effective medium theory. In addition to the synergistic solar and mid-IR dual-band tuning, our electrochromic device can tune the thermal emissivity with 0.85 contrast based on non-volatile and reversible metal electrodeposition, bringing vast opportunities for applications in space heat management, and thermal camouflage.