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 by two different alignment techniques. For the copolymer, the crystalline and liquid crystalline state were found to differ only slightly and alignment was achieved in the crystalline state, whereas the two phases differ substantially for the polyfluorene and alignment could be obtained in the liquid crystalline state. Light emitting diodes of differing structures were developed using the two materials as emissive layers. In the case of the polyfluorene, a state-of-the-art polarization ratio of 21 was realized.