Optical properties of La2O3 and HfO2 for radiative cooling via multiscale simulations

Abstract Radiative cooling materials have gained prominence as a zero-energy solution for mitigating global warming. However, a comprehensive understanding of the atomic-scale optical properties and macroscopic optical performance of radiative cooling materials remains elusive, limiting insight into the underlying physics of their optical response and cooling efficacy. La 2 O 3 and HfO 2 , which represent rare earth and third/fourth subgroup inorganic oxides, respectively, show promise for radiative cooling applications. In this study, we used multiscale simulations to investigate the optical properties of La 2 O 3 and HfO 2 across a broad spectrum. First-principles calculations revealed their dielectric functions and intrinsic refractive indices, and the results indicated that the slightly smaller bandgap of La 2 O 3 compared to HfO 2 induces a higher refractive index in the solar band. Additionally, three-phonon scattering was found to provide more accurate infrared optical properties than two-phonon scattering, which enhanced the emissivity in the sky window. Monte Carlo simulations were also used to determine the macroscopic optical properties of La 2 O 3 and HfO 2 coatings. Based on the simulated results, we identified that the particle size and particle volume fraction play a dominant role in the optical properties. Our findings underscore the potential of La 2 O 3 and HfO 2 nanocomposites for environment-friendly cooling and offer a new approach for high-throughput screening of optical materials through multiscale simulations.