Pure red organic electroluminescent devices using a novel europium(III) complex as emitting layer

Stable vacuum deposition of a new europium(III) complex, Eu(DBM)(3)(L) {DBM = dibenzoylmethanato, L = 3-ethyl-2-(4'-dimethylaminophenyl)imidazo[4,5-f] 1,10-phenanthroline}, were verified by ultraviolet-visible and infrared spectroscopy. By using the vacuum deposited film of the Eu(III) complex as the emitting layer, aluminum tris(8-hydroxyquinolinate) (AlQ) as electron-transporting layer, 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) as hole-blocking layer, N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-diphenyl-4,4'-diamine (TPD) as hole-transporting layer, a four-layer electroluminescent device of (+)indium-tin oxide/TPD(40 nm)/Eu(DBM)(3)(L)(40 nm)/BCP(10 nm)/AlQ(40 nm)/Mg:Ag(110 nm)/Ag(60 nm)(-) gave high efficient and pure red light emission with a luminance of 230 cd/m(2). A comparison of the electroluminescence properties of the four-layer device with those of a two-layer and a three-layer device was made. (C) 2004 Elsevier B.V. All rights reserved.