Photoluminescence and Electroluminescence in Combination of Rare-Earth Metal Complexes and Phosphorescent Molecules
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0965-S04-02
Photoluminescence and Electroluminescence in Combination of Rare-Earth Metal Complexes and Phosphorescent Molecules Zenken Kin1, Yuichi Hino1, Hirotake Kajii1, Yasuchika Hasegawa2, Tsuyoshi Kawai2, and Yutaka Ohmori1 1 Center for Advanced Science and Innovation, Osaka University, 2-1 Yamada-oka, Suita, 5650871, Japan 2 Graduate School of Materials Science, Nara Institute of Science and Technology, 8916-5 Takayama-cho, Ikoma, 630-0192, Japan
ABSTRACT We investigated luminescent properties of rare-earth metal complexes and phosphorrescent molecules doped in a conducting polymer. Electroluminescent (EL) properties in combination of a red emissive europium complex of tris(di-benzoylmethane)-mono(4,7-diphenylphenanthroline) europium (III) (Eu(dbm)3phen) and a blue phosphorescent molecule of bis[(4,6-difluoro-phenyl)-pyridinato-N,C2’] (picolinate) iridium (III) (FIrpic) doped in poly(Nvinyl-carbazole) (PVK) and a new rare-earth complex tris(hexafluoroacethylacetonato) (phenanthroline) samarium(III) [Sm(hfa)3(phen)2] have been investigated as an EL emitter. White EL has been obtained from mixed layer of Eu(dbm)3phen and FIrpic, and EL from Sm complex has been obtained. Energy transfer and the emission mechanisms have been discussed. INTRODUCTION Organic light-emitting diodes (OLEDs) have attracted attention because they have potential application for full color and flat panel displays [1-3]. A great number of research works have been concentrated in organic materials such as small molecules and conjugated polymers. However, a great part of these materials shows broad emission spectra. The rare earth ions, such as europium (Eu3+) [4], terbium (Tb3+) [5], thulium (Tm3+) [6], and neodymium (Nd3+) [7] complexes exhibit bright and spectrally narrow red, green and blue emission, respectively. For Eu complex, photoluminescence (PL) and electroluminescence (EL) originate from the 5 D0→7Fj transition, where j = 0,1···6 of the Eu3+ ion [4]. On the other hand, phosphorescent organic light-emitting diodes (PHOLEDs) fabricated using phosphorescent dyes have demonstrated high external quantum efficiencies [8-10]. Phosphorescence derives from either direct injection into the triplet metal ligand charge transfer state (3MLCT), or intersystem crossing (ISC) via the singlet charge transfer state (1MLCT). Additionally, the Eu complex and phosphorescent molecules mixed system was hardly studied. Under standing the energy transfer mechanism and the improvement of emission from Eu complex [11] will be useful for the organic optical devices by using sharp emission spectrum.
There are some reports on OLEDs with rare-earth complex, however, the samarium (Sm) complex has been less studied than Eu and Tb complexes, taking into consideration that the Sm3+ ion in general presents low fluorescence intensity. In this report, we discuss the energy transfer between the Eu complex and phosphorescent dye, and discuss the optical and electroluminescent (EL) properties of tris(hexafluoroacethylacetonato) (phenanthroline)samarium(III) [Sm(hfa)3
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