Two-Dimensional Hexagonal Boron Nitride Nanosheet as an Ion-Capturing Planar-Alignment Agent in a Liquid Crystal-Based Electro-Optic Device

The two-dimensional (2D) hexagonal boron nitride (h-BN) nanosheet is employed as a planar-alignment agent on one side of a liquid crystal (LC) cell, where the other side of the cell has a standard planar-aligning polyimide (PI) layer. The LC exhibits uniform planar-alignment in this h-BN/PI hybrid cell. The free-ion impurities in the LC are found to be suppressed dramatically in this h-BN/PI hybrid cell compared to that in a standard PI/PI LC cell. The free-ion concentration is reduced in the hybrid cell due to the 2D h-BN nanosheet’s ion-capturing process. The reduction of ionic impurities results in an accelerated electro-optic response of the LC in the hybrid cell. The dielectric anisotropy of the LC is enhanced in the h-BN/PI hybrid cell, indicating an improved orientational order parameter of the LC due to the reduction of ionic impurities.