Colored and paintable bilayer coatings with high solar-infrared reflectance for efficient cooling

Yijun Chen; Jyotirmoy Mandal; Wenxi Li; Ajani Smith-Washington; Cheng-Chia Tsai; Wenlong Huang; Sajan Shrestha; Nanfang Yu; Ray P S Han; Anyuan Cao; Yuan Yang

doi:10.1126/sciadv.aaz5413

Colored and paintable bilayer coatings with high solar-infrared reflectance for efficient cooling

Sci Adv. 2020 Apr 24;6(17):eaaz5413. doi: 10.1126/sciadv.aaz5413. eCollection 2020 Apr.

Authors

Affiliations

¹ Department of Applied Physics and Applied Mathematics, Columbia University, New York, NY 10027, USA.
² Department of Materials Science and Engineering, College of Engineering, Peking University, Beijing 100871, China.
³ Department of Mechanical Engineering, Columbia University, New York, NY 10027, USA.
⁴ Department of Physics and Astronomy, College of Arts and Sciences, Howard University, Washington, DC 20059, USA.

Abstract

Solar reflective and thermally emissive surfaces offer a sustainable way to cool objects under sunlight. However, white or silvery reflectance of these surfaces does not satisfy the need for color. Here, we present a paintable bilayer coating that simultaneously achieves color and radiative cooling. The bilayer comprises a thin, visible-absorptive layer atop a nonabsorptive, solar-scattering underlayer. The top layer absorbs appropriate visible wavelengths to show specific colors, while the underlayer maximizes the reflection of near-to-short wavelength infrared (NSWIR) light to reduce solar heating. Consequently, the bilayer attains higher NSWIR reflectance (by 0.1 to 0.51) compared with commercial paint monolayers of the same color and stays cooler by as much as 3.0° to 15.6°C under strong sunlight. High NSWIR reflectance of 0.89 is realized in the blue bilayer. The performances show that the bilayer paint design can achieve both color and efficient radiative cooling in a simple, inexpensive, and scalable manner.

Copyright © 2020 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC).