84 research outputs found
Highly suppressed solar absorption in a daytime radiative cooler designed by genetic algorithm
No full text© 2021 Sunae So et al., published by De Gruyter, Berlin/Boston 2021.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.11Ysciescopu
Spectrally Sharp Plasmon Resonances in the Near Infrared: Subwavelength Core-shell Nanoparticles
No full textSubwavelength plasmonic nanostructures have demonstrated many interesting phenomena and applications in recent decades. However, plasmonic resonance and associated properties, such as strong field enhancement, are limited to the visible regime due to the quasistatic nature of subwavelength plasmonic nanoparticles. Here, we numerically demonstrate spectral resonance tuning of subwavelength nanoparticles with a high-index core and a plasmonic shell while maintaining a sharp spectral peak. These core-shell-based nanoparticles have predominantly nonradiative loss and strong near-field enhancement due to their subwavelength feature size. This scheme can be further extended for magnetic and chiral meta-atoms. We suggest that these features of subwavelength core-shell-based nanoparticles are advantageous for many interesting applications including photothermal devices, enhanced light-matter interaction, and photonic circuitry.11Nsciescopu
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