Harnessing the synergy of ZrO2 and SiO2 dielectric micro-/nanoparticles in polymer-based photonic films for robust passive daytime radiative cooling

Polymer-based materials emerge as promising building blocks for passive daytime radiative cooling (PDRC) due to their affordability and ease of production. Enhancing these polymers with inorganic particle doping has shown to boost their mechanical properties and light scattering ability, a result of the increased refractive index contrast with air. However, the incorporation of a single type of inorganic particle often falls short in optimizing overall performance. Herein, we introduce a novel approach by simultaneously integrating high refractive index ZrO2 and wide band gap SiO2 dielectric particles into polydimethylsiloxane (PDMS) matrix. This dual-particle strategy synergistically improves the radiative cooling capabilities of the resulting photonic film. Remarkably, with a thickness of 1000 μm, it achieves an impressive 96.7% reflection of solar irradiance, while maintaining a high emissivity of 95.2% in the atmospheric window. Under solar intensity of ∼ 836.7 W·m-2, it delivers an average cooling power of 82.42 W·m-2, achieving a substantial sub-ambient temperature drop of up to 8.26 °C. We further explored its effectiveness in enhancing freshwater collection efficiency, leveraging its radiative cooling properties. Furthermore, the photonic film also exhibits versatile properties including flexibility, hydrophobicity, thermal stability, color scalability, and weather resistance, thus enhancing its suitability for various practical applications.