Passive daytime radiative cooling, which is a process that removes excess heat to cold space as an infinite heat sink, is an emerging technology for applications that require thermal control. Among the different structures of radiative coolers, multilayer- and photonic-structured radiative coolers that are composed of inorganic layers still need to be simple to fabricate. Herein, we describe the fabrication of a nanoparticle-mixture-based radiative cooler that exhibits highly selective infrared emission and low solar absorption. Al2O3, SiO2, and Si3N4 nanoparticles exhibit intrinsic absorption in parts of the atmospheric transparency window; facile one-step spin coating of a mixture of these nanoparticles generates a surface with selective infrared emission, which can provide a more powerful cooling effect compared to broadband emitters. The nanoparticle-based radiative cooler exhibits an extremely low solar absorption of 4% and a highly selective emissivity of 88.7% within the atmospheric transparency window owing to the synergy of the optical properties of the material. The nanoparticle mixture radiative cooler produces subambient cooling of 2.8 °C for surface cooling and 1.0 °C for space cooling, whereas the Ag film exhibits an above-ambient cooling of 1.1 °C for surface cooling and 3.4 °C for space cooling under direct sunlight.
Bibliographical noteFunding Information:
This research was supported by the Creative Materials Discovery Program (NRF-2018M3D1A1058972) through the National Research Foundation of Korea (NRF) funded by the Ministry of Science and ICT (MSIT), Republic of Korea and the International Research & Development Program of the NRF funded by MSIT (Grant No. 2019K1A47A02113032). D.C. and S.S. acknowledge the NRF Global Ph.D. fellowships (NRF-2019H1A2A1076622 and NRF-2017H1A2A1043322, respectively) funded by the Ministry of Education, Republic of Korea. This research was also supported by an NRF grant funded by the Korean government (MSIT) (No. 2020R1A2C3006382). J.R. acknowledges the Green Science Program funded by POSCO.
© 2021 American Chemical Society.
- atmospheric transparency window
- nanoparticle mixture
- passive daytime radiative cooling
- selective emitter
- subambient cooling
ASJC Scopus subject areas
- Materials Science(all)