A Janus Smart Window for Temperature-Adaptive Radiative Cooling and Adjustable Solar Transmittance

The advancement of sophisticated smart windows exhibiting superior thermoregulation capabilities in both solar spectrum and long-wave infrared range maintains a prominent objective for researchers in this field. In this study, a Janus window is proposed and prepared based on polymer-stabilized liquid-crystal films/thermochromic materials. It can achieve switchable front long-wave infrared emissivity (ε_Front) and solar modulation ability (ΔT_sol) through dynamic flipping, making it suitable for different seasonal energy-saving requirements. Outdoor experiments show that under daytime illumination, the indoor temperature decreases by 8 °C, and the nighttime temperature drops by 5 °C. MATLAB simulation calculations indicate that the daytime cooling power is 93 W m^-2, while the nighttime cooling power reaches 142 W m^-2. Interestingly, by modifying the conductive layer, it can effectively shield electromagnetic radiation (within the X-band frequency range (8.2-12.4) GHz). Energy simulation reveals the substantial superiority of this device in energy savings compared with single-layer polymer-stabilized liquid crystal, poly(N-isopropyl acrylamide), and normal glass when applied in different climate zones. This research presents a compelling opportunity for the development of sophisticated smart windows characterized by exceptional thermoregulation capabilities.