Characteristics of an electropolymerized PPV and its light-emitting diode

Poly(phenylene vinylene) (PPV) has been prepared successfully from p-xylylenebis(triphenylphosphonium bromide) in acetonitrile solution via an electroreduction polymerization. p-Xylylenebis(triphenylphosphonium bromide) also acted as an electrolyte in the solution. The resultant electropolymerized PPV film was transparent and dense, and had considerable adhesion to an indium-tin oxide (ITO) electrode. The electropolymerized PPV showed a blue shift both in the ultraviolet-visible absorption spectrum and photoluminescence, compared with the PPV prepared from a p-xylylenebis(tetrahydrothiophenium chloride) precursor route, indicating that it has a shorter pi-conjugated chain length. The infra-red absorption spectra showed a stable P-C bond on the electropolymerized PPV chain. The Al/electropolymerized PPV/ITO light-emitting diode emitted green light with an emission maximum at 530 nm. Annealing the electroluminescence device in a high vacuum oven at 160 degrees C for 3 h significantly enhanced the electroluminescence performance as a result of improvement of the interfacial contact between PPV and the Al metal electrode. Copyright (C) 1996 Elsevier Science Ltd.