Novel electroluminescent devices containing Eu3+-(2-acyl-1,3-indandionate) complexes with TPPO ligand

Abstract

Fabrication and electroluminescent properties of devices containing europium complexes of general formula [Eu(ACIND)3(TPPO)2], where ACIND, 2-acyl-1,3-indandionate ligands; and TPPO, triphenylphosphine oxide, as emitter layers are discussed. The double-layer devices based on these complexes present the following configurations: device 1: ITO/TPD/[Eu(AIND)3(TPPO)2]/Al; device 2: ITO/TPD/[Eu(ISOVIND)3(TPPO)2]/Al and device 3: ITO/TPD/[Eu(BIND)3(TPPO)2]/Al, where AIND, 2-acetyl-1,3-indandionate; ISOVIND, 2-isovaleryl-1,3-indandionate; and BIND, 2-benzoyl-1,3-indandionate, respectively. These devices exhibited photo and electroluminescent emissions. An important characteristic presented by devices is that their electroluminescent (EL) spectra, in the region of 5D0 → 7FJ (J = 0, 1, 2, 3 and 4) transitions of Eu3+ ion, show profiles that are different from photoluminescent (PL) ones. In addition to narrow bands arising from intraconfigurational-4f6 transitions, devices 1 and 2 also exhibited a broad band with maximum at around 500 nm which is assigned to electrophosphorescence from the indandionate ligands. On the other hand, EL spectra of device 3 present only narrow bands from 5D0 → 7FJ transitions. [Eu(ACIND)3(TPPO)2] complexes are promising candidates to prepare efficient organic light-emitting devices (OLEDs) when compared with those containing Eu3+-complexes of aliphatic β-diketonate anions.