An intelligent electrochromic film with passive radiative cooling and synergistic solar light control capabilities for displays and smart windows

Abstract

Polymer-dispersed liquid crystals (PDLCs) are promising candidates for electrically controlled applications in the fields of displays and smart windows due to their energy efficiency, convenience, and other advantages. However, the elevated operating voltage and limited temperature tolerance of these devices are not conducive to use in outdoor settings. In this study, fluorinated liquid crystal (LC) molecules with high clearing points were introduced to alter the physical properties of the LC mixture and the effects of their chemical structure on the electro-optical properties of PDLC films were investigated. The phase transition temperature of liquid crystals increased from 72.98 to 82.13 °C. They maintain a low drive voltage (<20 V) and a high contrast ratio (>70) when the temperature is raised from 0 °C to 60 °C. At the same time, they have a good modulation capability within the solar spectrum (ΔT_lum = 75.13 and ΔT_sol = 66.41). By adjusting the chemical structure of liquid crystal molecules and polymer monomers, the thin film exhibits high emissivity in the longwave infrared (LWIR) band (approximately 92%), promising excellent radiation efficiency. Simulated calculations show that the maximum cooling power during the day and night reaches 97.63 W⁻¹ m⁻² K⁻¹ and 136.24 W⁻¹ m⁻² K⁻¹ respectively. This work offers valuable insights for developing new intelligent devices in the fields of energy conservation and environmental protection.