The focus of this chapter is the application of reactive mesogens in organic lightemitting devices (OLEDs). OLEDs have attracted enormous interest since 1986 when C. Tang and S. vanSlyke described the first thin layer OLEDwith high brightness and a low operating voltage [1]. The basic structure and the materials used in C. Tang’s OLED are shown in Figure 11.1. Two different organic materials have been used, the electron conductor and green emitter tris(8-hydroxyquinoline)aluminum (Alq3) and the hole conducting aromatic amine 1,1-bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC). Both materials are deposited on top of an indium tin oxide (ITO) glass by vacuum evaporation.