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Materials 2019, 12(8), 1208; https://doi.org/10.3390/ma12081208

A Pragmatic Bilayer Selective Emitter for Efficient Radiative Cooling under Direct Sunlight

1,2,3, 1,2,3, 1,2,3,*, 1,2,3,4,*, 1,2,3,* and 1,2,3
1
State Key Laboratory of Materials-Oriented Chemical Engineering, College of Materials Science and Engineering, Nanjing Tech University, Nanjing 210009, China
2
Jiangsu Collaborative Innovation Center for Advanced Inorganic Function Composites, Nanjing Tech University, Nanjing 210009, China
3
Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing Tech University, Nanjing 210009, China
4
Key Laboratory of MEMS of Ministry of Education, Southeast University, Nanjing 210096, China
*
Authors to whom correspondence should be addressed.
Received: 18 January 2019 / Revised: 9 April 2019 / Accepted: 9 April 2019 / Published: 12 April 2019
(This article belongs to the Special Issue Thin Film Fabrication and Surface Techniques)
PDF [1265 KB, uploaded 12 April 2019]
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Abstract

Radiative cooling can make the selective emitter cool below ambient temperature without any external energy. Recent advances in photonic crystal and metamaterial technology made a high-efficiency selective emitter achievable by precisely controlling the emitter’s Infrared emission spectrum. However, the high cost of the photonic crystals and meta-materials limit their application. Herein, an efficient bilayer selective emitter is prepared based on the molecular vibrations of functional nanoparticles. By optimizing the volume fraction of the functional nanoparticles, the bilayer selective emitter can theoretically cool 36.7 °C and 25.5 °C below the ambient temperature in the nighttime and daytime, respectively. Such an efficient cooling performance is comparable with the published photonic crystal and metamaterial selective emitters. The rooftop measurements show that the bilayer selective emitter is effective in the ambient air even under direct sunlight. The relatively low cost and excellent cooling performance enable the bilayer selective emitter to have great potential for a practical purpose.
Keywords: radiative cooling; bilayer selective emitters; thermal radiation; functional thin films radiative cooling; bilayer selective emitters; thermal radiation; functional thin films
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Liu, Y.; Bai, A.; Fang, Z.; Ni, Y.; Lu, C.; Xu, Z. A Pragmatic Bilayer Selective Emitter for Efficient Radiative Cooling under Direct Sunlight. Materials 2019, 12, 1208.

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