Hybrid vanadium dioxide-liquid crystal tunable non-reciprocal scattering metamaterial smart window for visible and infrared radiation control

Abstract

Smart windows based on VO2 can control the infrared radiation entering the building based on the temperature, however, the visible part of the spectrum is not controlled. Liquid crystal (LC) based privacy windows, on the other hand, control the visibility either with temperature or applied voltage, however, the total transparency remains fixed as the scattering is mainly in the forward direction. To be able to control both the visibility and the temperature in the house, here we combine both layers in which the LC layer is made of a composite of nanoporous organic microparticles called Cochleates at small concentrations embedded in the LC matrix, thus acting as a tunable scattering metamaterial. The VO2-LC interface has less Fresnel reflectivity and therefore higher solar modulation is expected in an optimized window. In addition, being hidden under the LC layer, VO2 will be protected from oxidation. Electro-optic and thermo-optic properties of the device are investigated including the response time measurements. A non-reciprocity effect is observed showing better performance when the VO2 layer is facing the outside world, in which the window becomes more transparent from inside than from outside and also showing higher solar modulation. Response time is 1 ms for the rise and 10 ms fall time at 70 V. This approach opens up a new possibility of thermochromic VO2 and LC-based systems to satisfy the real-life requirements on smart window applications.

Broadband Modulation, Self‐Driven, and Self‐Cleaning Smart Photovoltaic Windows for High Efficiency Energy Saving Buildings

“…[22] However, relatively higher transmittance of SCPSLC in the NIR band is adverse to achieve an ideal energy-saving effect. To overcome this limitation, VO 2 nanoparticles, well known for their exceptional light modulation performance in the NIR band derived from an insulator-tometal phase transition (Table S1, Supporting Information), [23][24][25][26] are combined with SCPSLC to constructure the MCU. As presented in Figure S2 and Table S2, Supporting Information, the phase transition temperature of SCPSLC can be manipulated within a wide range from 40 to 60 °C via simply manipulating the proportion of liquid crystal in SCPSLC without affecting the light modulation performance.…”

Thermochromic Energy Efficient Windows: Fundamentals, Recent Advances, and Perspectives

“…A localized surface plasmon resonance effect from the isolated VO 2 nanoparticles (at the metallic state) was observed through a controllable etching process, which induced an excellent optical performance of T lum of 61.3% and ΔT sol of 11.9% (Figure 12). Long et al 223 successfully fabricated a metamaterial with an isolated VO 2 nanoparticle triangular-like unit array. Significantly enhanced luminous transmittance can be found due to the excellent antireflection properties of isolated VO 2 nanoparticles.…”

Advanced liquid crystal-based switchable optical devices for light protection applications: principles and strategies

“…A hybrid window made of nanoscale and microscale LCs and a layer of thermochromic material (VO 2 ) was demonstrated recently to fulfill this purpose, as shown in Fig. 16a 174 . Furthermore, many researchers tried doping NPs into P-LC materials to expand the modulation band while ensuring the fast response of light protection devices.…”

“…a Schematic illustration of the VO 2 -based LC-cochleate device and transmission spectra of the device plotted as a function of wavelength at different temperatures. Reproduced with permission from ref 174. .…”