Efficient radiative cooling emitter adopting the wavelength conversion of giant CdSe/ZnS core-shell nanocrystals

초록

Daytime radiative cooling is an eco-friendly, temperature-cooling mechanism that uses the inherent properties of a material without energy consumption. To realize a high daytime radiative cooling ability, it is necessary to minimize light absorption in the solar spectrum (0.3-2.5 mu m) and maximize the emissivity in the atmospheric transmittance window (8-13 mu m). Currently, the solar reflective layer of a radiative cooling material has the limitation of absorbing UV light, which can reduce the cooling performance. We attempted to solve this problem via UV-to-visible wavelength conversion using CdSe/ZnS giant core-shell structures. By applying this strategy, a wavelength conversion-type radiative cooling emitter (WC-RCE) was fabricated using "giant" CdSe/ZnS core-shell nanocrystals embedded into a polymeric membrane to establish minimized absorption within the UV and short-visible regions, which constitute up to 17.28% of the total solar spectrum. The applied g-NCs have a high photoluminescence quantum yield and a large Stokes shift, and can resolve the absorption in reflective layers, such as silver, by re-emitting the wavelength of the absorbed UV rays into the visible region. Compared with a conventional RCE, the WC-RCE achieves further cooling by 0.38 degrees C on average from outdoor measurements. Thus, a wavelength conversion strategy was confirmed for efficient daytime radiative cooling. (C) 2021 Published by Elsevier Ltd.

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