Design of efficient radiative emission and daytime cooling structures with Si₃N₄ and SiO₂ nanoparticle laminate films

Research on radiative cooling has attracted recent widespread interest owing to the potential for low-cost passive structures to enable large-scale thermal energy management. Using a generalized effective medium theory, we theoretically show that two-layer films comprised of SiO₂ and Si₃N₄ nanoparticle layers on an Ag back reflector exhibit superior radiative cooling compared to single-layer or two-layer dense solid films, and can outperform other reported designs. The performance enhancement is a result of the ability to tune the nanoparticle fill fraction, which improves the spectral match between emissivity of this structure and the atmospheric transmission window. We also propose a standardized method for comparing the performance of radiative cooling structures reported by the research community.