High-Performance Daytime Radiative Cooler and Near-Ideal Selective Emitter Enabled by Transparent Sapphire Substrate

Dongwoo Chae, Soomin Son, Yuting Liu, Hangyu Lim, Heon Lee

Research output: Contribution to journalArticlepeer-review

42 Citations (Scopus)


Daytime radiative cooling serving as a method to pump heat from objects on Earth to cold outer space is an attractive cooling option that does not require any energy input. Among radiative cooler structures, the multilayer- or photonic-structured radiative cooler, composed of inorganic materials, remains one of the most complicated structures to fabricate. In this study, transparent sapphire-substrate-based radiative coolers comprising a simple structure and selective emitter-like optical characteristics are proposed. Utilizing the intrinsic optical properties of the sapphire substrate and adopting additional IR emissive layers, such as those composed of silicon nitride thin film or aluminum oxide nanoparticles, high-performance radiative coolers can be fabricated with a low mean absorptivity (3–4%) at 0.3–2.5 µm and a high mean emissivity of over 90% at 8–13 µm. Experiments show that the fabricated radiative coolers reach temperature drops of ≈10 °C in the daytime. From the theoretical calculations of radiative cooling performance, the sapphire-substrate-based radiative coolers demonstrate a net cooling power as high as 100 Wm−2.

Original languageEnglish
Article number2001577
JournalAdvanced Science
Issue number19
Publication statusPublished - 2020 Oct 1


  • atmospheric transparency window
  • daytime radiative cooling
  • selective emitters
  • transparent sapphire substrates

ASJC Scopus subject areas

  • Medicine (miscellaneous)
  • Chemical Engineering(all)
  • Biochemistry, Genetics and Molecular Biology (miscellaneous)
  • Materials Science(all)
  • Engineering(all)
  • Physics and Astronomy(all)


Dive into the research topics of 'High-Performance Daytime Radiative Cooler and Near-Ideal Selective Emitter Enabled by Transparent Sapphire Substrate'. Together they form a unique fingerprint.

Cite this