Europium complexes as emitters in organic electroluminescent devices

Using two different trivalent europium (Eu3+) complexes, europium(dibenzoylmethanato) 3(bathophenanthroline) [Eu(DBM) 3bath] and europium (dibenzoylmethanato) 3(monophenanthroline) [Eu(DBM) 3phen], with different ligands for emission-layer materials, various types of electroluminescent (EL) devices have been fabricated. Combined with a triphenylamine derivative (TPD) and an oxadiazole derivative (OXD7) as hole-transport-layer materials, two-layer- and three-layer-type devices have been fabricated. We find that these two emission-layer materials have similar EL spectra, but their EL performances are different. The EL capability of the Eu complexes and their carrier-transporting characteristics are largely dependent on the ligands.