RESUMO
Smart windows with synergetic light modulation have heightened demands for applications in smart cars and novel buildings. However, improving the on-demand energy-saving efficiency is quite challenging due to the difficulty of modulating sunlight with a broad bandwidth in an energy-saving way. Herein, a smart window with switchable near-infrared light transmittance and passive radiative cooling is prepared via a monomer design strategy and photoinduced polymerization. The effects of hydrogen bonds and fluorine groups in acrylate monomers on the electro-optical properties as well as microstructures of polymer-dispersed liquid crystal films have been systematically studied. Some films show a high contrast ratio of 90.4 or a low threshold voltage (Vth) of 2.0 V, which can be roll-to-roll processed in a large area. Besides, the film has a superior indoor temperature regulation ability due to its passive radiative cooling and controllable near-infrared light transmittance properties. Its radiative cooling efficiency is calculated to be 142.69 W/m2 and NIR transmittance could be switched to below 10%. The introduction of a carboxylic monomer and fluorinated monomer into the system endows the film with a highly efficient temperature management capability. The film has great potential for applications in fields such as flexible smart windows, camouflage materials, and so on.
RESUMO
Smart windows with radiative heat management capability using the sun and outer space as zero-energy thermodynamic resources have gained prominence, demonstrating a minimum carbon footprint. However, realizing on-demand thermal management throughout all seasons while reducing fossil energy consumption remains a formidable challenge. Herein, an energy-efficient smart window that enables actively tunable passive radiative cooling (PRC) and multimode heating regulation is demonstrated by integrating the emission-enhanced polymer-dispersed liquid crystal (SiO2@PRC PDLC) film and a low-emission layer deposited with carbon nanotubes. Specifically, this device can achieve a temperature close to the chamber interior ambient under solar irradiance of 700 W m-2, as well as a temperature drop of 2.3 °C at sunlight of 500 W m-2, whose multistage PRC efficiency can be rapidly adjusted by a moderate voltage. Meanwhile, synchronous cooperation of passive radiative heating (PRH), solar heating (SH), and electric heating (EH) endows this smart window with the capability to handle complicated heating situations during cold weather. Energy simulation reveals the substantial superiority of this device in energy savings compared with single-layer SiO2@PRC PDLC, normal glass, and commercial low-E glass when applied in different climate zones. This work provides a feasible pathway for year-round thermal management, presenting a huge potential in energy-saving applications.
