Perovskite quantum dots doped nematic liquid crystal composites: Influence on dielectric parameters and electrical conductivity

In the current study, we have reported the dispersion of inorganic perovskite quantum dots i.e., CsPbBr₃ PQDs in a cyanobiphenyl based nematic liquid crystal i.e., 5CB (4՛-pentyl-4-biphenylcarbonitrile) at different concentrations (0.1 wt%, 0.25 wt%, 0.5 wt%, and 1.0 wt%) and its effect on the dielectric and electrical parameters of the latter. The polarized optical micrographs were obtained for confirming the uniform and stable dispersion of PQDs in 5CB. Frequency dependent dielectric parameters (ε′, ε″, tan δ) were measured in the range of 20 Hz to 2 MHz using the dielectric spectroscopy. A higher value of ε′ was attained and a corresponding relaxation peak in ε″ and tan δ appeared due to the electrode polarization in low frequency region for composite system. The relaxation process was analyzed using Havriliak-Negami (HN) equation indicating a Debye-type relaxation in this region. The parallel component of permittivity has a lower value for PQDs-5CB composites than the Pure 5CB sample, while the perpendicular component does not change significantly and hence, dielectric anisotropy decreases when PQDs were mixed in LC matrix. Electrical conductivity was evaluated and found to be increased due to higher ionic density for composites. The DC conductivity was calculated by fitting the electrical conductivity data with Jonscher Power Law. The activation energy was computed using the Arrhenius equation. These results suggest that PQDs can be availed as a guest material for modulating the physical properties of LCs making them more efficient for tunable electronic devices.