Electromagnetic Simulation on Optical Performance of Thermochromic Film: Influences of Particle Size, Shape, Concentration, and Film Substrate

Abstract Thermochromic (TC) film possesses dynamic optical behaviors in response to change in environmental temperature, i.e., high solar reflectance during hot season and high solar absorptance during cold season. It has been proposed as an effective strategy to minimize energy use in buildings and improve indoor and outdoor thermal comfort. This study aims to computationally optimizing temperature-dependent optical properties of TC film in terms of particle size, shape, and volume concentration of TC pigment as well as film substrate. The computational system consists of electromagnetic simulation and Kubelka-Munk model. It has demonstrated that as particle size increases from 100 nm to 1000 nm, the total diffuse reflectance of TC film decreases from 10% to 2% below the transition temperature of TC pigment while decreases from 11% to 2% above the transition temperature. When changing particle shape from sphere to rod, the total diffuse reflectance of TC film is increased to 27% below the transition temperature and 31% above the transition temperature. Furthermore, with the substrate of aluminum, the total diffuse reflectance of TC film reaches up to 92%. Finally, as the TC pigment concentration increases from 5% to 50%, the total reflectance of TC film increases from 5% to 34%. This methodology provides guideline to tailor optical behaviors of optical film for better performance.