Polarized electroluminescence from highly aligned liquid crystalline polymers

Two classes of polymer materials, hexyl-dodecyl copoly(phenylene-ethynylene ) and poly(2,7-(9,9-di(ethylhexyl)-fluorene)), respectively, were aligned b y two different alignment techniques. For the copolymer, the crystalline an d liquid crystalline state were found to differ only slightly and alignment was achieved in the crystalline state, whereas the two phases differ subst antially for the polyfluorene and alignment could be obtained in the liquid crystalline state. Light emitting diodes of differing structures were deve loped using the two materials as emissive layers. In the case of the polyfl uorene, a state-of-the-art polarization ratio of 21 was realized. (C) 2000 Elsevier Science S.A. All rights reserved.