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

Abstract

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.