Banik Udayan, Agrawal Ashutosh, Meddeb Hosni, Sergeev Oleg, Reininghaus Nies, Götz-Köhler Maximilian, Gehrke Kai, Stührenberg Jonas, Vehse Martin, Sznajder Maciej, Agert Carsten
DLR Institute of Networked Energy Systems, 26129 Oldenburg, Germany.
DLR Institute of Space Systems, 28359 Bremen, Germany.
ACS Appl Mater Interfaces. 2021 May 26;13(20):24130-24137. doi: 10.1021/acsami.1c04056. Epub 2021 May 11.
Radiative cooling to subambient temperatures can be efficiently achieved through spectrally selective emission, which until now has only been realized by using complex nanoengineered structures. Here, a simple dip-coated planar polymer emitter derived from polysilazane, which exhibits strong selective emissivity in the atmospheric transparency window of 8-13 μm, is demonstrated. The 5 μm thin silicon oxycarbonitride coating has an emissivity of 0.86 in this spectral range because of alignment of the frequencies of bond vibrations arising from the polymer. Furthermore, atmospheric heat absorption is suppressed due to its low emissivity outside the atmospheric transparency window. The reported structure with the highly transparent polymer and underlying silver mirror reflects 97% of the incoming solar irradiation. A temperature reduction of 6.8 °C below ambient temperature was achieved by the structure under direct sunlight, yielding a cooling power of 93.7 W m. The structural simplicity, durability, easy applicability, and high selectivity make polysilazane a unique emitter for efficient prospective passive daytime radiative cooling structures.
通过光谱选择性发射可以有效地实现向低于环境温度的辐射冷却，到目前为止，这仅通过使用复杂的纳米工程结构来实现。在此，展示了一种由聚硅氮烷衍生的简单浸涂平面聚合物发射器，它在8-13μm的大气透明窗口中表现出很强的选择性发射率。由于聚合物产生的键振动频率的排列，5μm厚的碳氮氧化硅涂层在该光谱范围内的发射率为0.86。此外，由于其在大气透明窗口之外的低发射率，大气热吸收受到抑制。所报道的具有高透明聚合物和底层银镜的结构反射了97%的入射太阳辐射。在直射阳光下，该结构实现了比环境温度低6.8°C的降温，产生了93.7W/m的冷却功率。结构简单、耐用、易于应用和高选择性使聚硅氮烷成为用于高效潜在被动日间辐射冷却结构的独特发射器。
