Research on liquid crystal-based smart windows for application of building-integrated solar power system

Smart windows are active windows that can adjust transmittance and can perform functions such as energy saving, indoor illumination control in conjunction with smart lighting or daylighting, user privacy protection, and active space separation. Smart window technology has high potential to expand not only to buildings but also to next-generation mobility fields such as electric vehicles and air taxis. Types of smart windows include electrochromic type(EC), polarized particle type(PP), and liquid crystal type(LC). In the case of liquid crystal systems, polymer dispersed liquid crystal systems (PDLC) are being developed the most. However, the PDLC has the advantage of fast response speed, but has the disadvantage of high driving voltage and difficulty in realizing color. In this study, we developed a liquid crystal-based smart window capable of low-power operation and color implementation that can be combined with building-integrated solar power to save energy in buildings. In order to realize color, dyes were developed in a way that did not affect the liquid crystal. And in order to apply it to building windows, we developed a liquid crystal smart window that can operate without a polarizer for arrangement of liquid crystals, which is different from the existing liquid crystal method by considering transmittance. As a result of measuring the color, operating voltage, and current of the liquid crystal smart window, the CIE-LAB index difference for color was 20.86 (L: 41.33 → 34.23, a: - 10.43 → -3.25, b: -9.88 → -3.3), The voltage was 5V and the current was 4.14X10-7[A]. In addition, the driving voltage and current result was 2.07uW, confirming that low-power driving was possible.