Smart Thermally Switchable Liquid Crystal Window

Abstract

Global warming, due to the consumption of fossil energy, is one of the biggest challenges in recent days. Air conditioning (cooling and heating) of office and residential buildings is one of the largest energy consumptions. One way to reduce the energy consumption is to use switchable architectural windows, which can control radiant energy flow. Herein, a smart thermally switchable window with transmittance sensitive to ambient temperature is reported. This smart window is based on a liquid crystal (LC) whose orientation varies with temperature. At temperatures lower than a low threshold temperature, such as in winter, the LC orients perpendicular to the window substrate, and the window is transparent and lets sunlight pass it to warm interiors of buildings. At temperatures higher than a high threshold temperature, such as in summer, the LC orients parallel to the substrate. The window becomes absorbing and blocks sunlight, resulting in a reduction of the solar heating. When temperature varies between these two thresholds, the window has gray‐level transmittances. It does not use electricity and is very energy‐saving, and has an immense potential in applications of smart architectural and vehicle windows.

Thermochromic Materials for Smart Windows: A State-of-Art Review

“…Further research could focus on various strategies for integration, especially for perovskites, which have shown potential for demonstrating several features beyond thermochromism; 2) Besides the three major thermochromic materials discussed in the review, exploring new materials with novel thermochromic mechanisms will help expand the range of potential candidates. For example, ionic liquids, liquid crystals (Jiang et al, 2021), and metamaterials have shown promising thermochromic properties; 3) Finally, the durability and safety of materials should be considered, especially for materials requiring encapsulation of gas or liquid. The leakage of thermo-responsive materials may lead to a dramatic decline in performance.…”

Liquid Crystals: Versatile Self-Organized Smart Soft Materials

“…A thermally switchable smart window with variable transmittance according to the ambient temperature has been demonstrated. 211 The operation of this smart window is based on temperature dependent orientation of the LC molecules. The LC molecules orient perpendicular to the substrate at low temperature and thus create a transparent state.…”

“…Upon exposure to near-infrared light, the carbon nanotubes absorb the energy and drive the device to alter its transmittance. A thermally switchable smart window with variable transmittance according to the ambient temperature has been demonstrated . The operation of this smart window is based on temperature dependent orientation of the LC molecules.…”

Recent Progress in Liquid Crystal‐Based Smart Windows: Materials, Structures, and Design

“…Thermochromism LC-based smart windows tune their transmittance or color according to the ambient temperature. [121,122] Compared with electrochromism, thermochromism is a passive technology to regulate the optical states of such smart windows. This mechanism is considered as a good candidate for building energy conservation because the light modulation of the smart windows can be achieved in response to the dynamic environmental temperature automatically without extra energy consumption.…”