Measurement of triplet exciton diffusion in organic light-emitting diodes
Measurement of triplet exciton diffusion in organic light-emitting diodes
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DOI：
10.1103/physrevb.81.245201
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发表时间：
2010-06
影响因子：
3.7
通讯作者：
J. Wünsche;S. Reineke;B. Lüssem;K. Leo
中科院分区：
文献类型：
--
作者：
J. Wünsche;S. Reineke;B. Lüssem;K. Leo
详细研究了有机发光二极管中三重态激子在-二-1-萘基-二苯基-[1,1':4',1":4",1‴-四联苯]-4,4‴-二胺（4P-NPD）层中的扩散。测量荧光主体材料中三重态扩散长度的适当方法是通过插入不同厚度的主体间隔层将激子产生位点与辐射三重态衰变位点空间分离。然而，需要考虑空腔效应、间隔层边界处激子的猝灭和阻挡以及传感层中的直接电荷载流子复合。我们使用专门设计的层堆叠，排除了空腔效应对测量的影响，并使用强淬火传感层，确保边界条件明确。通过实验研究了传感层、生成区和直接载流子复合对激子的猝灭，并讨论了它们对提取扩散长度的影响。该分析中三重态-三重态湮灭的重要性是通过电流相关评估来估计的。提出了传感层发射对间隔物厚度依赖性的分析模型，其中包括重要的影响。通过这种方式，我们找到了 4P-NPD 的三重态扩散长度。
A detailed investigation of the diffusion of triplet excitons in a layer of-di-1-naphthalenyl--diphenyl-[1,1′:4′,1″:4″,1‴-quaterphenyl]-4,4‴-diamine (4P-NPD) incorporated in organic light-emitting diodes is presented. An appropriate method to measure the triplet diffusion length in fluorescent host materials is the spatial separation of the site of exciton generation from the site of radiative triplet decay by inserting a host spacer layer of varying thickness. However, cavity effects, the quenching and blocking of excitons at the boundaries of the spacer layer, and direct charge-carrier recombination in the sensing layer need to be taken into account. We use a specially designed layer stack, which excludes the influence of cavity effects on the measurements and a strongly quenching sensing layer, which ensures well-defined boundary conditions. The quenching of excitons by the sensing layer, the generation zone, and direct charge-carrier recombination are investigated experimentally and their influence on the extracted diffusion length are discussed. The significance of triplet-triplet annihilation in this analysis is estimated by a current-dependent evaluation. An analytic model for the dependence of the sensing layer emission on the spacer thickness is presented, which includes the important effects. By this means, we find a triplet diffusion length ofin 4P-NPD.