Construction of a ternary channel efficient passive cooling composites with solar-reflective, thermoemissive, and thermoconductive properties

Current passive radiative cooling is a promising alternative to electrical cooling systems, but it is still difficult to be used in cooling devices with an internal heat source. Hence, we here present a ternary channel efficient passive cooling composites by embedding hexagonal boron nitride (h-BN) into high-density polyethylene (HDPE). Like the traditional passive radiative cooling materials, the h-BN/HDPE composite possesses a high solar reflectance (~87%) that minimizes solar heat gain, and a high thermal emittance (~0.71) that maximizes radiative heat loss, but the composites also have a high thermal conductivity (~1.47 W/(m·K)) that maximizes the internal heat conduction. Therefore, the combination of the optical and thermal properties allows for the LED's temperature drops of 5 °C, compared with the bare LED, under the average solar intensity of 1100 W/m². The notably cooling effect provides the guidance for the future application of the ternary channel efficient passive cooling composites in cooling the devices with internal heat.