凹凸界面结构对磷光材料器件性能影响的研究

Influence of Concavo-Convex Interface Structure on Performance of Phosphorescent Material Device

以有机电致磷光器件ITO/NPB/CBP+Ir(ppy)3/Li F/Al为研究对象,在该器件中,CBP(4,4'-N,N'-二咔唑联苯)为主体材料,Ir(ppy)3(三(2-苯基吡啶)铱)为磷光掺杂剂,NPB为空穴传输层。然后在参考器件的NPB/CBP+Ir(ppy)3界面处构建了凹凸结构,制备了一系列凹凸发光层的磷光器件。通过电流密度-电压-亮度曲线、电流效率-电压曲线考察了不同凹凸发光层磷光器件的电致发光性能,并分析了这些器件的界面电荷俘获以及注入电荷动力学。研究结果发现,当凸起个数为3个时,器件的最大电流效率为22 cd/A,与传统结构器件相比提高了26%。电流效率的提高主要归结于以下两个原因:一方面,凹凸结构拓宽了载流子复合界面的面积,从而减弱了三线态激子-三线态激子的淬灭;另一方面,凹凸结构有利于减弱器件的光波导效应,增强器件内部的光耦合输出效率。

In this paper, a traditional phosphorescent organic light emitting device （PHOLED） with the structure of ITO /NPB（N, N0-bis（naphthalen-l-yl）-N, N0-bis（phenyl）-benzidine） /CBP（ 4, 4＇-N, N＇-two carbazole biphenyl ）： Ir （ PPY ） 3 （ three （ 2-phenyl pyridine ） Iridium ） / liF / Al was selected as reference, in which CBP was used as the host material, Ir （ppy） 3 served as phosphorescent dopant, NPB served as a hole transport layer. Then, the concavo-convex shape was introduced into the NPB/CBP： Ir（ppy） 3 interface of reference device, to structure a series of different concavo- convex emitting layer phosphorescent devices. The electroluminescence performance of above devices was carefully investi- gated by using the current density-voltage-brightness and current efficiency-voltage curve, with further analysis on device interface charge trapping and injected charge dynamics. The results indicate that when the convex number is 3, the maxi- mum current efficiency of this device is 22 cd/A, 26% higher than traditional structure device. The improvement of effi- ciency in concavo-convex shape emitting layer devices is attributed to the following reasons： on the one hand, concavo- convex shape emitting layer broadens the carrier recombination zone of device, further suppresses the triplet-triplet （T-T） annihilation; on the other hand, concavo-eonvex shape emitting layer can weaken wave guiding effects, inducing an improved light extraction efficiency.