Efficient full-color daytime radiative cooling with diffuse-reflection-dominant cholesteric liquid crystals

Abstract

Imparting colors to radiative coolers is essential for expanding their practical utility. We herein present the demonstration of a new route to achieve diffuse-colored radiative coolers using self-assembled cholesteric liquid crystals (CLCs). A full-color spectrum is enabled by controlling the chiral dopant concentration and is predominantly generated through diffuse Bragg reflection due to the wavy layers formed during spin coating. Because of C-O/C-O-C stretching in LC242 molecules, the CLCs achieve radiative cooling by emitting infrared through the atmospheric window. When placed between an Ag reflector and polydimethylsiloxane, CLC realizes a solar reflectance of 94 % and thermal emissivity of 0.9. Consequently, under a solar irradiance of 1050 +/- 10 W m(-2), it achieves a temperature that is 3.1 +/- 0.5 degrees C and 30.8 +/- 0.3 degrees C lower than those of air and a commercial paint, respectively, and exhibits a cooling power of 19.5 W m(-2). Our approach promises new opportunities in the field of colored radiative cooling.