Multifunctional metallophosphors with anti-triplet–triplet annihilation properties for solution-processable electroluminescent devices
作者:Gui-Jiang Zhou、Wai-Yeung Wong、Bing Yao、Zhiyuan Xie、Lixiang Wang
DOI:10.1039/b718653c
日期:——
With the goal to provide organometallic triplet emitters with good hole-injection/hole-transporting properties, highly amorphous character for simple solution-processed organic light-emitting diodes, and negligible tripletâtriplet (TâT) annihilation, a series of new phosphorescent cyclometalated IrIII and PtII complexes with triphenylamine-anchored fluorenylpyridine dendritic ligands were synthesized and characterized. The photophysical, thermal, electrochemical and electroluminescent properties of these molecules are reported. The incorporation of two sterically hindered electron-rich triphenylamino groups to the 9-position of the fluorene skeleton was found not only to afford triplet emitters in the glassy state with high Tg, but also to elevate the HOMO levels and confer the hole-injection ability to the phosphorescent center. These highly amorphous metal phosphors can serve as doped emitters in a small molecular host for spin-coated emission layer in suitable OLED structures to achieve good device performance with a maximum luminance of 29380 cd mâ2 at 23 V, a peak external quantum efficiency of 7.0%, a luminance efficiency of 21.4 cd Aâ1 and a power efficiency of 2.9 lm Wâ1. Both the electrophosphorescent device characterization as well as the theoretical simulation results show that these iridium electrophosphors show negligible TâT annihilation even at high operating current densities and moderately high doping levels. Our investigations indicate that attaching the triphenylamino moieties to the fluorene ring is an effective way to overcome the TâT annihilation caused by the strong interactions among the emitting molecules.
为了提供具有良好载流子注入/载流子运输性质、高度无定形特性以便简单溶液加工的有机发光二极管,并且在三重态-三重态(T-T)湮灭方面可以忽略不计,合成并表征了一系列新的磷光环金属IrIII和PtII络合物,这些络合物具有锚定于三苯胺的荧蒽吡啶树枝状配体。报告了这些分子的光物理性质、热性能、电化学性质和电致发光性质。研究发现,将两个立体阻碍的富电子三苯胺基团加入到荧蒽骨架的9位,不仅能够在玻璃态下提供具有高玻璃转变温度(Tg)的三重态发射体,还能提高最高占据分子轨道(HOMO)能级,并赋予磷光中心良好的载流子注入能力。这些高度无定形的金属磷光体可以作为掺杂发射体,应用于适合的有机发光二极管结构的小分子宿主中的旋涂发射层,以实现良好的器件性能,最大亮度为29380 cd m⁻²,工作电压为23 V,峰值外量子效率为7.0%,亮度效率为21.4 cd A⁻¹,功率效率为2.9 lm W⁻¹。无论是电磷光器件的特性测试还是理论模拟结果均表明,这些铱电磷光体在高工作电流密度和适中掺杂水平下表现出几乎可以忽略不计的T-T湮灭。我们的研究表明,将三苯胺基团连接到荧蒽环上是一种有效的方法,可以克服发射分子间强相互作用导致的T-T湮灭。