Effect of Perovskite Quantum Dots on the Dielectric Properties of a Nematic Liquid Crystal Material

Abstract

Dispersion of quantum dots (QDs) in liquid crystal (LC) medium can effectively modify their dielectric and electro-optical properties which can be useful in LC based display as well as non-display applications. Here, we reported the effect of doping of perovskite quantum dots (PQDs) on the dielectric properties of a nematic liquid crystal (NLC) material namely ZLI-1565 throughout its nematic and isotropic phases. The dielectric parameters of pure NLC and its composites with PQDs (0.1 wt.%, 0.25 wt.% and 0.5 wt. %) were observed in the frequency range of 20 Hz - 2 MHz.The value of dielectric permittivity (ε') and dielectric loss (ε") increases in composites as compared to pure NLC in the low frequency region due to the increment in the mobile ion density. The spectral peak of loss factor (tan δ) of pure NLC shifts towards the high frequency region with the addition of PQDs. Moreover, the temperature dependent dielectric parameters were also evaluated for pure NLC and 0.25 wt.% PQDs-NLC composite (i.e. optimum concentration). Moreover, the dielectric anisotropy and threshold voltage were also evaluated for pure sample and 0.25 wt.% composite. A point to be noted here that the clearing temperature (TN-I) of 0.25 wt.% composite is reduced by ~4 °C as compared to pure NLC. The results obtained on such PQDs-NLC composites could be utilized in the fabrication of NLC based electrical devices with tunable dielectric features.