Realizing Electro-Optic Switching and Radiative Cooling in Smart Window Films via Fluorinated Monomer Doping

Building energy consumption, driven by the escalating demand for cooling, necessitates the development of innovative smart windows capable of dynamic solar modulation and thermal management. Polymer-dispersed liquid crystal (PDLC) devices are promising candidates but are hindered by high driving voltages and a lack of passive radiative cooling capabilities. Herein, we propose a facile strategy to fabricate multifunctional PDLC smart windows by incorporating fluorinated monomers with distinct chemical structures into the polymer matrix. Through the addition of fluorine atoms, the phase separation process was improved, and the matrix surface free energy was decreased. Consequently, the constraint on liquid crystal molecules was significantly alleviated, which led the threshold and saturation voltages to drop to one-third of the values found in the control group. Simultaneously, the strong vibrational absorption of C-F bonds within the 8-13 μm atmospheric transparency window endowed the films with exceptional mid-infrared emissivity (exceeding 0.9), enabling passive radiative cooling without external energy input. Under a solar irradiance of 500 W/m², the film exhibited a subambient cooling performance of 1.5 °C. The results demonstrated that tailored fluorinated monomers bridge the gap between active electro-optical modulation and passive thermal management, presenting a potential strategy for sustainable building facades.