Electro-optical and dielectric properties of TiO₂ nanoparticles in nematic liquid crystals with high dielectric anisotropy

The electrical, optical and dielectric performance of high-dielectric-constant TiO₂ nanoparticles (NPs) dispersed in nematic liquid crystals (NLCs) with high dielectric anisotropy is demonstrated. TiO₂ doping decreases the pretilt angle of the NLC cell because of the increase in Van der Waals interaction between the NLC molecule and alignment layer. Moreover, TiO₂ doping strengthens the electric field in the NLC bulk and suppresses the ionic screen effect on the substrate surface, thus decreasing the threshold and driving voltages of the NLC cell. The measured field-off response time and estimated conductivity initially increase and then decrease with increased TiO₂ concentrations. This phenomenon is due to the antagonism between the entrained ion impurities during fabrication and the ion harvest effect of TiO₂ NPs. Dielectric spectral measurements reveal that TiO₂ doping changes the relative permittivity and dielectric anisotropy of NLCs because of the changed space–charge polarisation and order parameters in the NLC bulk. The physical mechanisms are discussed in detail accordingly.