Study of Energy Transfer and Triplet Exciton Diffusion in Hole-Transporting Host Materials
Study of Energy Transfer and Triplet Exciton Diffusion in Hole-Transporting Host Materials
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DOI：
10.1002/adfm.200900357
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发表时间：
2009-10-09
影响因子：
19
通讯作者：
Thompson, Mark E.
中科院分区：
文献类型：
--
作者：
Wu, Chao;Djurovich, Peter I.;Thompson, Mark E.
使用了一种器件结构，其中OLED的空穴传输层(HTL)掺杂有荧光或磷光发射体，即阳极/HTL主体/空穴阻滞剂/电子传输层/阴极。HTL主体具有更高的HOMO能量，允许空穴在不被掺杂剂分子捕获的情况下被传输，从而避免在掺杂剂上直接复合。主体和掺杂剂之间HOMO能量的非常规失配使得能够研究这些主体/客体系统中的能量传递和OLED器件HTL主体层中的三重态激子扩散，而不会出现掺杂电荷陷阱的复杂情况。这里考察的主体材料是四芳基对苯二胺。数据表明，这些主体与器件中发光掺杂剂之间的Forster能量传递是低效的，三重态激子在这些主体材料中的扩散与分子结构和分子间相互作用的程度密切相关。与密度泛函理论计算和光物理测量结果一致，含有萘基的主体材料比含苯基的主体材料表现出更长的三重态激子扩散长度。
A device structure is used in which the hole-transporting layer (HTL) of an OLED is doped with either fluorescent or phosphorescent emitters, that is, anode/HTL-host/hole blocker/electron-transporting layer/cathode. The HTL hosts have higher HOMO energy allowing holes to be transported without being trapped by dopant molecules, avoiding direct recombination on the dopant. The unconventional mismatch of HOMO energies between host and dopant allow for the study of energy transfer in these host/guest systems and triplet exciton diffusion in the HTL-host layers of OLED device, without the complication of charge trapping at dopants. The host materials, examined here are tetraaryl-p-phenylenediamines. Data shows that Forster energy transfer between these hosts and emissive dopant in devices is inefficient Triplet exciton diffusion in these host materials is closely related to molecular structure and the degree of intermolecular interaction. Host materials that contain naphthyl groups demonstrate longer triplet exciton diffusion lengths than those with phenyl substituents, consistent with DFT calculations and photophysical measurements.