Using Graphene As Transparent Electrodes And Alignment Layers For Liquid Crystal Devices

Using Graphene As Transparent Electrodes And Alignment Layers For Liquid Crystal Devices - Electronics Featured Graphene
Figure 1: (a) A schematic representation of a conventional LC cell containing a layer of ITO and a layer of polyimide coating with unidirectional rubbing on each glass slide, (b) the picture of a conventional LC cell, (c) a schematic representation of a graphene-based cell which contains a single layer of on each glass slide, (d) the picture of a graphene-based LC cell, (e) A schematic representation of the alignment of nematic LC molecules on graphene due to – electron stacking. The ellipsoids are LCs and the black honeycomb structure is the graphene surface. The LC molecular structure is shown in the ellipsoid on the graphene surface. The ?-? electron stacking is illustrated by matching the LC’s benzene rings on the graphene-honeycomb structure. (click on image to enlarge)

Liquid crystals (LC) are technologically important for their wide applications in optical displays—known as liquid crystal displays (LCD). In conventional LCDs, the LC material is contained in conventional LC cells, where the polyimide layers are used to align the LC homogeneously in the cell, and the transmissive indium tin oxide (ITO) electrodes are used to apply the electric field to reorient the LC along the field.

Associate Professor Rajratan Basu and his student Midshipman Samuel Shalov in the Department of Physics at the United States Naval Academy have experimentally demonstrated that monolayer graphene on the two glass substrates can function concurrently as the LC alignment layers and the transparent electrodes to fabricate an LC cell, without using the conventional polyimide and ITO substrates.

This replacement can effectively decrease the thickness of all the alignment layers and electrodes from about 100 nm to less than 1 nm. The transmission of the graphene film is more that of the ITO film. Reducing this effective thickness could offer the potential to minimize the transmissive losses and optimize throughput of light over a wide range of spectral bands for modern backlit LCDs.

 

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