Colored radiative cooling structure assisted by near-infrared fluorescence

Abstract

Radiative cooling is a process by which spontaneous cooling below ambient temperature is achieved without energy input, even under direct sunlight. Materials and structures that possess such properties are promising solutions to combat the current global energy consumption increase. However, commercial applications of these radiative coolers are hindered by the fact that they must necessarily be white or silvery like a mirror to achieve the best cooling performances. Previous research has been focused on absorbing parts of the visible spectrum and compensating by improving mid-IR emission. In this paper, a novel colored radiative cooler is presented that incorporates a near-IR fluorophore to re-radiate solar energy absorbed in the visible region. The overall structure and chromaticity of the reflected color is optimized and the cooling performance is theoretically calculated. We demonstrate that the structure can achieve below-ambient cooling for a fluorescence conversion ratio greater than 0.5.