High-Contrast and Energy Efficient Optical Light shutter: Dispersion of Metal-doped Carbon Quantum Dots in Cholesteric Liquid Crystals

Abstract

Cholesteric liquid crystals (CLCs) are emerging multifunctional photonic materials owing to their unique selective reflection and electro-optical properties, enabling applications in smart windows, optical shutters, sensors, lasers, optical security, anti-counterfeiting, and advanced photonic applications. The integration of metal-doped carbon quantum dots (MCQDs) into CLC mixtures offers potential for advanced characteristics. In this work, pure CLC and MCQDs-dispersed CLC mixtures were prepared using nematic LC (E7), chiral (R1011), and MCQDs (zinc-doped carbon quantum dots). The textural, electro-optical, and dielectric characterization of the pure and dispersed CLCs was performed and reported herein. The observed textural and electro-optical behaviour revealed a 19.11% reduction in switching voltage and a 41.34% improvement in contrast ratio with dispersion of MCQDs compared with the pure CLC. Moreover, the improved dielectric permittivity (ε' = 15.98 at 10 kHz) and a shift in relaxation frequency from 6.71 × 10 ^5 Hz (pure CLC) to 13.5 × 10 ^5 Hz indicates faster dielectric responses in CLC dispersed with MCQDs. Thus, the dispersion of MCQDs in the CLC mixture resulted in an advancement in materials promising for energy-efficient smart windows and optical shutters, etc.

Keywords: Cholesteric liquid crystal; smart windows; contrast ratio