Suppressed-scattering spectral windows for radiative cooling applications

The scattering of light by resonant nanoparticles is a key process for enhancing the solar reflectance in daylight radiative cooling. Here, we investigate the impact of material dispersion on the scattering performance of popular nanoparticles for radiative cooling appli-cations. We show that, due to material dispersion, nanoparticles with a qualitatively similar response at visible frequencies exhibit fundamentally different scattering properties at infrared frequencies. It is found that dispersive nanoparticles exhibit suppressed-scattering windows, allowing for selective thermal emission within a highly reflective sample. The existence of suppressed-scattering windows solely depends on material dispersion, and they appear pinned to the same wavelength even in random composite materials and periodic metasurfaces. Finally, we investigate calcium-silicate-hydrate (CSH), the main phase of concrete, as an example of a dispersive host, illustrating that the co-design of nanoparticles and host allows for tuning of the suppressed-scattering windows. Our results indicate that controlled nanoporosities would enable concrete with daylight passive radiative cooling capabilities.(c) 2023 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

Automated summary

This study investigates the influence of material dispersion on the scattering performance of nanoparticles for daylight radiative cooling. It reveals that nanoparticles with similar responses at visible frequencies exhibit fundamentally different scattering properties at infrared frequencies due to material dispersion. These dispersive nanoparticles show suppressed-scattering windows, enabling selective thermal emission within a highly reflective sample. The existence of suppressed-scattering windows depends solely on material dispersion and remains fixed at the same wavelength even in random composite materials and periodic metasurfaces. Additionally, calcium-silicate-hydrate (CSH), the main component of concrete, is explored as an example of a dispersive host, showing that the co-design of nanoparticles and host material allows for tuning of the suppressed-scattering windows. The results suggest that controlled nanoporosity can enable concrete with passive radiative cooling capabilities.