Abstract
Here, we report a selective multilayer emitter for eco-friendly daytime passive radiative cooling. The types of materials and thickness of up to 10 layers of the multilayer structure are optimized by a genetic algorithm. The passive radiative cooler is designed to mainly target low solar absorption, which allows sub-ambient cooling under direct sunlight. We used a custom objective function in the solar region to achieve high-performance daytime radiative cooling to minimize solar absorption. The designed structure minimizes solar absorption with an average absorptivity of 5.0% in the solar region (0.3-2.5 μm) while strongly emitting thermal radiation with an average emissivity of 86.0% in the atmospheric transparency window (8-13 μm). The designed and fabricated structure achieves daytime net cooling flux of 84.8 W m-2 and 70.6 W m-2, respectively, under the direct AM 1.5 solar irradiation (SI) (total heat flux of 892 W m-2 in the 0.3-2.5 μm wavelength region). Finally, we experimentally demonstrate a passive radiative cooling of the fabricated selective emitter through a 72-hour day-night cycle, showing an average and maximum temperature reduction of 3.1 °C and 6.0 °C, respectively. Our approach provides additional degrees of freedom by designing both materials and thickness and thereby is expected to allow high-performance daytime radiative cooling.
Original language | English |
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Pages (from-to) | 2107-2115 |
Number of pages | 9 |
Journal | Nanophotonics |
Volume | 11 |
Issue number | 9 |
DOIs | |
Publication status | Published - 2022 Apr 1 |
Keywords
- computational optimization
- multilayer structures
- radiative cooling
- selective emitters
ASJC Scopus subject areas
- Biotechnology
- Electronic, Optical and Magnetic Materials
- Atomic and Molecular Physics, and Optics
- Electrical and Electronic Engineering