Photo and electroluminescence of a phenylene vinylene conjugated polymer containing bipirydine units and chelated europium complex

Abstract

A conjugated polymer, poly[5,5'-(2,2′-bipyridylene)vinylene-alt-2,5-(1,4-bis(octyloxy)vinylene)] (PBPyVOctV), was synthesized by the polymerization of 5,5′-divinyl-2,2′-bipyridine with 1,4-dibromo-2,5-bis(octyloxy) benzene through a Heck cross-coupling reaction. Then, a metallopolymer, PBPyVOctV-Eu(tta)3, was obtained by the bipyridine chelating coordination of PBPyVOctV with europium (Eu(III)) complex, Eu(tta)3.xH2O (where tta is 2-thenoyltrifluoroacetonate). The incorporation of an europium center into the polymer backbone changed the optical and electronic properties of the conjugated polymer. The photoluminescence of the materials and electroluminescence properties of solution-processed organic light-emitting diodes (OLEDs) consisting of composites of PVK as a host with PBPyVOctV, Eu(tta)3.xH2O or PBPyVOctV-Eu(tta)3 as guests were studied. The diode containing PVK:PBPyVOctV-Eu(tta)3 as emissive layer delivered the highest luminance and highest current efficiency, with an orange color emission, as a result of combined emissions from the europium ions and polymer structure.