Application of monolayer WSe₂ as the planar-alignment agent in an electro-optic liquid crystal device

Two-dimensional (2D) tungsten diselenide (WSe₂) nanosheets were transferred onto indium tin oxide (ITO) coated glass slides. Two such 2D WSe₂-covered ITO glass slides were placed together to fabricate a liquid crystal (LC) cell. A nematic LC inside this WSe₂-based cell exhibits uniform planar-alignment. This planar-alignment at the molecular scale is achieved due to the coherent overlay of the LC molecules along the selenium (Se) array on the WSe₂ lattice. This WSe₂-based LC device shows the typical electro-optical effect when an electric field is applied via ITO electrodes. This electro-optical effect also reveals a standard Fréedericksz transition of the LC, confirming that the 2D WSe₂, as the planar-alignment agent, supplies adequate planar anchoring energy—which can be overcome by the Fréedericksz threshold voltage.