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


Affiliations
1 Department of Physics, Aligarh Muslim University, Aligarh 202 002 (U.P.), India
2 Department of Applied Physics, Amity Institute of Applied Science, Amity University Uttar Pradesh, Noida 201 313, India

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 (ɛʹ) and dielectric loss (ɛʺ) 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.

Keywords

Nematic liquid crystal; Quantum dots; Dielectric permittivity
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  • Effect of Perovskite Quantum Dots on the Dielectric Properties of a Nematic Liquid Crystal Material

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Authors

Asif Ali Ansari
Department of Physics, Aligarh Muslim University, Aligarh 202 002 (U.P.), India
Jai Prakash
Department of Physics, Aligarh Muslim University, Aligarh 202 002 (U.P.), India
Nidhia
Department of Physics, Aligarh Muslim University, Aligarh 202 002 (U.P.), India
Aafreena
Department of Physics, Aligarh Muslim University, Aligarh 202 002 (U.P.), India
Shikha Chauhan
Department of Physics, Aligarh Muslim University, Aligarh 202 002 (U.P.), India
Gautam Singh
Department of Applied Physics, Amity Institute of Applied Science, Amity University Uttar Pradesh, Noida 201 313, India

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 (ɛʹ) and dielectric loss (ɛʺ) 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.

Keywords


Nematic liquid crystal; Quantum dots; Dielectric permittivity