Abstract
A planar liquid crystal (LC) cell is designed by placing together a monolayer graphene coated glass slide and a planar-aligning polyimide layer on an indium tin oxide (ITO) coated glass slide. It is shown that the monolayer graphene film on one side of the cell can serve as the planar-alignment agent. At the same time, the monolayer graphene film also functions as the transparent electrode. The successful optical and electro-optical operations of this hybrid LC cell with monolayer graphene on one side and with ITO and associated planar-aligning polyimide on the other side are demonstrated. The measured optical transmission of the graphene electrode is found to be much better than that of the combined ITO-PI layers. The electro-optical effect and the dynamic electro-optic response of the LC in this graphene-polyimide-based hybrid cell reveal the typical director reorientation of the LC on the application of an electric field.
Highlights
One atomic layer thick two-dimensional (2D) monolayer graphene (MGP) [1,2] shows high optical transparency [3], high electrical conductivity [4], high chemical resistance [5], and mechanical flexibility [5]
Since MGP has a few advantages over indium tin oxide (ITO) electrodes, such as better mechanical strength, higher chemical resistance, and higher mechanical flexibility, several reports in the literature have shown that MGP can serve as an ITO replacement in an liquid crystal (LC) device [11,12,13,14,15,16]
It is demonstrated that the two-dimensional MGP sheet can serve both as the planar-alignment agent and the transparent electrode, simultaneously, at one side of the cell
Summary
One atomic layer thick two-dimensional (2D) monolayer graphene (MGP) [1,2] shows high optical transparency [3], high electrical conductivity [4], high chemical resistance [5], and mechanical flexibility [5]. It is, difficult to obtain a unidirectional planar alignment of the LC on MGP on a large scale. It is experimentally verified that the two-dimensional MGP film can function as a planar-alignment agent on one side in the hybrid cell which has a rubbed PI layer on the other side We fabricated another cell with a rubbed PI layer on one side and a plain glass slide (with no MGP) on the other side. As the cell was rotated by 45°, the rubbing direction of the PI became parallel to the polarizer, and the micrograph in Fig. 3(g) shows a non-uniform dark texture This proves that the absence of the MGP on one side of the cell disrupts the unidirectional planar-alignment
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