Design and optimization of PDMS-based passive radiative cooling coatings

Abstract Passive daytime radiative cooling lowers surface temperature without external power by reflecting solar radiation and emitting heat through the 8 - 13 um atmospheric window. This paper develops an integrated thermo-optical modeling and optimization framework for PDMS-based passive radiative cooling coatings, combining thin-film spectral analysis, multi-objective structural optimization, and robustness evaluation under practical uncertainties. A single-layer spectral-emissivity model is first established with thin-film optics and the transfer matrix method, then coupled with an energy-balance model to evaluate net cooling power under daytime conditions. To improve the thickness sensitivity of the single-layer baseline, a multilayer structure composed of PDMS, SiO 2 , Al 2 O 3 , and TiO 2 is optimized under multiple objectives, including solar rejection, window emissivity, thickness, and cost. A practical thermo-optical model further tests the optimized design under environmental forcing and manufacturing uncertainty. The results show that PDMS keeps low emissivity in the solar band, its atmospheric-window emissivity rises with thickness and gradually saturates, and the optimized multilayer design improves cooling performance while retaining practical robustness.