Suppressed-scattering spectral windows for radiative cooling applications.

Area of Science:

• Nanophotonics and Materials Science
• Optics and Photonics
• Thermal Engineering

Background:

• Daylight radiative cooling utilizes resonant nanoparticles to enhance solar reflectance.
• Understanding material dispersion is crucial for optimizing nanoparticle scattering performance.
• Current research focuses on tailoring nanoparticle properties for efficient radiative cooling.

Purpose of the Study:

• To investigate the influence of material dispersion on nanoparticle scattering for radiative cooling.
• To identify how dispersion affects scattering properties across different frequencies.
• To explore the potential of dispersive materials for tunable thermal emission.

Main Methods:

• Theoretical analysis of light scattering by resonant nanoparticles.
• Numerical simulations to model scattering performance with material dispersion.
• Investigation of suppressed-scattering windows in various material compositions.
• Experimental validation using calcium-silicate-hydrate (CSH) as a dispersive host.

Main Results:

• Material dispersion fundamentally alters infrared scattering properties of nanoparticles, despite similar visible frequency responses.
• Dispersive nanoparticles exhibit suppressed-scattering windows, enabling selective thermal emission within highly reflective materials.
• These suppressed-scattering windows are wavelength-pinned and independent of material arrangement (random composites or periodic metasurfaces).
• Co-design of nanoparticles and dispersive hosts, like CSH, allows for tuning of these windows.

Conclusions:

• Material dispersion is a critical factor in designing nanoparticles for radiative cooling.
• Suppressed-scattering windows offer a pathway for achieving selective thermal emission and enhanced cooling.
• Controlled nanoporosities in materials like concrete could lead to passive radiative cooling capabilities.