An optimized self-adaptive thermal radiation turn-down coating with vanadium dioxide nanowire array

• Published in: International journal of heat and mass transfer Vol. 191; p. 122835
• Main Authors: Araki, Ken, Zhang, Richard Z.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01-08-2022; Elsevier BV
• Subjects: Arrays; Coating; Computational Optimization; Cooling; Emittance; Fabry-Perot Cavity; Fabry-Perot interferometers; Far infrared radiation; High temperature; Incident light; Insulators; Metasurface; Multilayers; Nanowire; Nanowires; Optimization; Parameter identification; Phase transitions; Photovoltaic cells; Refractivity; Self-Adaptive Radiative Cooling; Solar cells; Thermal radiation; Thickness; Thin films; Turn-Down; Vanadium Dioxide; Vanadium oxides; Turn-Down; Self-Adaptive Radiative Cooling; Nanowire; Fabry-Perot Cavity; Metasurface; Vanadium Dioxide; Computational Optimization
• ISSN: 0017-9310; 1879-2189
• DOI: 10.1016/j.ijheatmasstransfer.2022.122835

Insulator-to-metal temperature phase transition Vanadium Dioxide (VO2) can enable radiative property switching in the mid- to far-infrared wavelengths. With computational optimization of grating arrangement and layer thickness parameters, we identify a monolithic high-performance turn-down thermal emittance coating of no more than 2 μm thick, consisting of a VO2 sub-wavelength nanowire grating array on an index-matched Fabry-Perot dielectric thin film on an additional absorbing VO2 sublayer. The working principles of this optimized VO2 structure are its gradient refractive index allowing high through-coating transmittance in the cold state, and its near-unity emissivity from semi-metal-insulator-metal plasmonic coupling in the hot state. This anisotropic patterned structure also considers performance over polarized incident light. A survey of other Fabry-Perot cavity materials with refractive index matching points to higher turn-down performances given an optimal VO2 nanowire volume filling ratio. With 24-hour solar and environmental analysis in comparison to other VO2 metasurfaces and multilayers, this coating enables responsive passive radiative cooling at high temperatures exceeding transition. This nano/micro-patterned coating could potentially impact self-cooling of the solar cells, batteries, and electrical devices where risk presents at high temperatures.
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