Chae Dongwoo, Son Soomin, Liu Yuting, Lim Hangyu, Lee Heon
Department of Materials Science and Engineering Korea University Anam-ro 145, Seonguk-gu Seoul 136-713 Republic of Korea.
Adv Sci (Weinh). 2020 Aug 18;7(19):2001577. doi: 10.1002/advs.202001577. eCollection 2020 Oct.
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.
日间辐射冷却作为一种将地球上物体的热量泵送到寒冷外层空间的方法，是一种无需任何能量输入的有吸引力的冷却选择。在辐射冷却器结构中，由无机材料组成的多层或光子结构辐射冷却器仍然是最难制造的结构之一。在本研究中，提出了一种基于透明蓝宝石衬底的辐射冷却器，其结构简单且具有类似选择性发射体的光学特性。利用蓝宝石衬底的固有光学特性并采用额外的红外发射层，如由氮化硅薄膜或氧化铝纳米颗粒组成的发射层，可以制造出高性能的辐射冷却器，其在0.3-2.5微米处的平均吸收率较低（3-4%），在8-13微米处的平均发射率超过90%。实验表明，制造出的辐射冷却器在白天可实现约10°C的温度下降。从辐射冷却性能的理论计算来看，基于蓝宝石衬底的辐射冷却器展现出高达100 W/m²的净冷却功率。
