铕配合物共掺杂电致发光器件效率滚降的延缓(英文)

Suppression of Efficiency Roll-off in Co-doped Electroluminescent Devices Based on Europium Complex

将Alq3[tris(8-hydroxyquinoline)aluminium]和Eu(TTA)3phen(TTA=thenoyltrifluoroacetone,phen=1,10-phenanthroline)共掺杂进入主体材料CBP(4,4′-N,N′-dicarbazole-biphenyl)中,我们制作并研究了一系列电致发光器件。经过优化Alq3的掺杂浓度,在不改变色纯度的情况下,器件的效率滚降被大幅降低并获得了近乎加倍的最大亮度。发光层中的Alq3分子不仅促进了电子的注入和传输,还延缓了空穴的传输。借助电致发光光谱,我们证实Alq3分子作为阶梯加速空穴从CBP分子到Eu(TTA)3phen分子的迁移,从而促进了电子和空穴在Eu(TTA)3phen分子上的平衡。因此,我们认为器件的效率滚降受到抑制的原因有两点:一是复合区间的加宽,二是Eu(TTA)3phen分子上空穴和电子的分布更加平衡。

By co-doping Alq3[tris（8-hydroxyquinoline） aluminum] and Eu（TTA）3phen （TTA=thenoyltrifluoroacetone, phen=1,10-phenanthroline） into CBP （4,4＇-N,N＇ dicarbazole -biphenyl）, a series of electroluminescent （EL） devices were fabricated and investigated. After optimizing the co-doping concentration of Alq3, significant suppression of EL efficiency roll-off and almost doubled maximum brightness were realized without deteriorating the color purity. The presence of Alq3 molecules in light-emitting layer （EML） not only facilitates the injection and transport of electrons but also retards the transport of holes. Alq3 molecules function as ladders of hole transfer from CBP to Eu（TTA）3phen molecules as supported by the EL spectroscopy results, thus facilitating the balance of holes and electrons on Eu（TTA）3phen molecules. Therefore, two possible reasons are suggested to be responsible for the suppression of EL efficiency roll-off： one is the broadening of recombination zone, the other is the improved balance of holes and electrons on Eu（TTA）3phen molecules.