Simulation of optical properties of thermochromic film: Influences of particle configuration and geometry

Abstract

Thermochromic (TC) materials are one of smart materials which could reversibly change colors/optical properties in response to the variation in environmental temperature. TC film with embedded TC pigment, facilitates temperature management of infrastructures to improve energy efficiency of buildings and durability of pavement. However, the effectiveness of TC film is dictated by its optical properties. This study aims to optimizing temperature-dependent optical behaviors of TC film in terms of particle configuration and geometry of TC pigment by conducting finite element simulation and applying Kubelka-Munk model. The analysis shows that TC film with bi-sphere particles achieves total diffuse reflectance of 10% for dark-colored TC pigment and 11% for light-colored TC pigment, which is negligibly affected by particle configuration. When changing particle shape from sphere to rod, the total diffuse reflectance of TC film is enhanced to 16% below the transition temperature and 18% above the transition temperature. Moreover, as the length to diameter ratio of nanorod increases, the total diffuse reflectance of TC film decreases. The computational framework provides guideline to optimize the design of TC film with desirable optical properties of TC film.