Effect of electronic and phonon properties on polar dielectric embedded polymer-based radiative cooling materials

Polar dielectric embedded polymer-based radiative cooling (RC_PDP) materials are more attractive since they can not only achieve daytime radiative cooling but also be fabricated on a large scale at a low cost. In this paper, we propose a screening method for dielectric particles with high absorption capacity in the solar spectrum based on electronic energy band structures. We derive the dielectric function of dielectric particles using the four-parameter semi-quantum (FPSQ) model and determine the optical properties of the dielectric particles through the FDTD simulation and Mie theory. Then, we obtain the electromagnetic wave attenuation depth of the hybrid material accounting for the derived effective complex refractive index. Finally, the proposed method is validated with experiments. The results show that the calculated emissivity of the hybrid material is in high agreement with the measurement. Furthermore, α-SiO₂ is the most suitable dielectric particle for RC_PDP materials among the selected dielectric particles of α-SiO₂, α-Al₂O₃, TiO₂, and SiC. This work provides a theoretical explanation for the high performance of RC_PDP materials and a theoretical guide for the selection of substrates for achieving radiative cooling.