High contrast ratio light-emitting liquid crystal device based on AIEE dyes

In this paper, we have fabricated a light-emitting liquid crystal device (LELCD) with high contrast ratio (CR) using aggregation-induced emission enhancement (AIEE) dye, a photoluminescent (PL) material connected with liquid crystals (LCs) on weak surface anchoring boundaries. This LELCD can continually vary the PL intensity by controlling the direction of AIEE-dye molecules following the orientation of the LCs responding to the strength of the electric field. In order to check the effect of surface anchoring on the CR of this device, we used both horizontal and vertical alignment layers. For the horizontal alignment layer, we investigated the effect of CR at three different types of alignment layers with different anchoring energy and at different rubbing conditions for each alignment layer. For the vertical alignment layer, changes in the CR according to the rubbing strength were observed. Additionally, our study was conducted on the impact of LELCD cell thickness variations on the CR. Consequently, we achieved CR of about 30:1 at LELCD with cell thickness of 10 µm using polymethyl methacrylate as a horizontal alignment layer with weak surface anchoring boundary. This is the best result to date for CR of display devices using AIEE. We anticipate that the results of this study can be applied to optical devices and various other applications.