Reversed Yolk-Shell Dielectric Scatterers for Advanced Radiative Cooling

Passive daytime radiative cooling dissipates heat from surfaces by reflecting sunlight and emitting infrared radiation to the cold outer space, featuring a zero-energy consumption. Polymer-dielectric radiative cooling coatings have received significant attention because of their scalable preparation, low cost, and ease of use. However, current dielectric scatterers reveal limited solar reflectance in the polymer-dielectric coatings due to the optical crowding, which reduces cooling effect and hinders practical application. Employing a scalable emulsion templated method, reversed yolk-shell dielectric scatterers (RYSS) are developed to alleviate optical crowding effects in polymer-dielectric coatings. This results in coatings with a solar reflectance of approximate to 97.4% and an infrared emittance of approximate to 96.9%, while achieving a substantial reduction in scatterers content. Besides, simulation results show that RYSS outperforms core-shell, hollow, and solid scatterers in enhancing solar reflectance. Using phase change materials as emulsion templates, RYSS with high heat storage effectively enhance daytime cooling and reduce nighttime over-cooling. Moreover, cooling experiments on concentrating photovoltaics demonstrate a temperature drop of 42 degrees C (approximate to 26.2 times extension of lifetime) and a notable 22% increase in open-circuit voltage. This work suggests that RYSS presents a promising solution to overcome the challenges of radiative cooling materials and pave the way for their practical applications. Passive daytime radiative cooling utilizes surface reflection and infrared emission for zero-energy cooling. Polymer-dielectric coatings, due to scalability and cost-effectiveness, are favored. However, optical crowding limits solar reflectance. Here, reversed yolk-shell scatterers (RYSS) are synthesized achieving approximate to 97.4% reflectance, surpassing core-shell, hollow, and solid scatterers, indicating RYSS as a promising solution for radiative cooling material challenges and practical applications. image