Europium β-diketonates for red-emitting electroluminescent devices

Organic light-emitting devices were fabricated, wherein europium β-diketonates of the general formula Eu(X)3(L) are the active emitting materials [L = 2,4,6-tri(2-pyridyl)-1,3,5-triazine (TPTZ) or 4,4′-dimethoxy-2,2′-bipyridine (dmbipy); X is the conjugate base of 4,4,4-trifluoro-1-phenyl-1,3-butanedione (HBTFA), thenoyltrifluoroacetone (HTTA), or 1,1,1,5,5,5-hexafluoro-2,4-pentanedione (HHFAC)]. Red luminescence characteristic of Eu(III) at about 614 nm was observed in each of the five devices of the general device configuration ITO/NPB/Eu(X)3(L):CBP/BCP/AlQ/LiF/Al [ITO, indium tin oxide; NPB, 4,4′-bis[n-(1-naphthyl)-N-phenyl-amino]biphenyl; CBP, 4,4′-N,N′-dicarbazolebiphenyl; BCP, 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline; AlQ, tris(8-hydroxy)quinoline aluminum]. Except for Eu(BTFA)3(TPTZ), each of the other four complexes gave practically meaningful device performance. In particular, the device utilizing Eu(TTA)3(TPTZ) exhibited a maximum brightness of 781 cd/m2 and the highest current efficiency reported so far of 4.76 cd/A at a typical computer screen brightness (100 cd/m2).