Chemical vapor deposition of poly(p-phenylene vinylene) based light emitting diodes with low turn-on voltages

We report fabrication of single layer poly (p-phenylene vinylene) (PPV) light emitting diodes with low turn-on voltages by chemical vapor deposition of dihalo p-xylenes. Devices made from dibromo p-xylene exhibit turn-on fields of 2 x 10(6) V/cm, which is in good agreement with solution processed PPV devices. Devices made from dichloro p-xylene, however, have significantly lower turn-on fields of 6.5 x 10(5) V/cm. The electroluminescent output of bilayer PPV/tris (8-hydroxyquinoline) aluminum devices made from the two monomers suggests that the chlorine based polymer may have improved electron transport characteristics compared to solution processed polymer, which is tentatively attributed to residual chlorine from the thermal conversion process. (C) 1997 American Institute of Physics.