Concentration effect of Cadmium Selenide Sulphide/Zinc Sulphide quantum dots on electro-optic and dielectric properties in nematic liquid crystals composite

In this work, we have studied concentration effect of Cadmium Selenide Sulphide/Zinc Sulphide (CdSeS/ZnS) quantum dots (QDs) dispersed on liquid crystalline material, 4-pentyl-4′-cyanobiphenyl nematic liquid crystal (5CB NLC). We used the dielectric spectroscopy technique to obtain electrical and dielectric properties for pure 5CB and doped with QDs form. To observe the effect of CdSeS/ZnS QDs concentration, 5CB was dispersed with 0.05, 0.1 and 0.15 % wt/wt CdSeS/ZnS QDs. Some physical parameters such as real part of dielectric permittivity (ε′), imaginary part of dielectric permittivity (ε"), loss tangent (tanδ), dielectric anisotropy (Δε′) and ac conductivity (σac) of pure 5CB NLC and CdSeS/ZnS QDs doped 5CB NLC composite were measured in the frequency range of 1 kHz-10 MHz at various bias voltages by using dielectric spectroscopy technique at room temperature. In addition, the threshold voltage (Vth) and splay elastic constant (K11) parameters were calculated dependent on doping concentration. The current-voltage (I-V) characteristics of the samples were also investigated. The results showed that the electro-optic and dielectric parameters change significantly with CdSeS/ZnS QDs doping and which were explained by the molecular interaction mechanism between LC molecules and CdSeS/ZnS QDs.