Colored, Daytime Radiative Coolers with Thin-Film Resonators for Aesthetic Purposes

Recently developed approaches in passive radiative cooling enable daytime cooling via engineered photonic structure layouts. However, the use of these daytime radiative coolers is restricted owing to their nonaesthetic appearance resulted from strong solar reflection. Therefore, this article introduces a colored passive radiative cooler (CPRC) capable of generating potential cooling power, based on a thin-film optical resonator embedded in an efficient thermal emission structure. This CPRC not only selectively emits infrared wave through the atmospheric transparency window but also displays subtractive primary colors to exhibit the desired appearance. Theoretical analysis and systematic experiments prove the possibility of subambient cooling via CPRC by lowering the temperature to 3.9 degrees C below the ambient air in the daylight. This is the first example of coloring radiative cooler by photonic structures. Successful demonstration of cooling/coloring behavior with wearable electronic devices under solar irradiation represents a major step forward in the field of temperature-sensitive, flexible, wearable electronic/optoelectronic devices.