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.
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