Robust luminogens with thermally activated delayed fluorescence (TADF) and aggregation-induced emission (AIE) characteristics are desirable for high efficiency, low efficiency roll-off and low-cost organic light-emitting diodes (OLEDs). Derived from the 2,4,5,6-tetra(carbazol-9-yl)-1,3-dicyanobenzene (4CzIPN) framework, two TADF-characterized luminogens, 4CzIPN-MO and 4CzPhIPN-MO, are presented in this paper. Encouragingly, along with the carbazole fragment modification of 4CzIPN by using methoxy groups, an unexpected AIE behavior can be observed as for 4CzPhIPN-MO with the insertion of phenyl-bridges between the carbazole moieties and the central benzene ring. The advantages of the novel designed 4CzPhIPN-MO structure are found to be capable to reduce the injection barrier, suppress nonradiative decay, and increase the solid-state photoluminescence (PL) efficiency. Consequently, the nondoped OLED performs outstandingly with a maximum EQE of 14.5%, and extremely low efficiency roll-off of 3.8% and 3.9%, respectively, at a luminance of 100 and 1000 cd m⁻², which is among the best EQE roll-off performance of nondoped solution-processed TADF OLEDs reported so far. This work demonstrates that the manipulation of the molecular topologies is a promising and practical strategy for achieving efficient and stable solution-processed OLEDs.

中文翻译：

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操纵空间阻碍效应，以实现AIE和TADF，以实现高效非掺杂溶液处理的OLED，且效率极低。

具有高效率，低效率滚降和低成本有机发光二极管（OLED）的具有热激活延迟荧光（TADF）和聚集诱导发射（AIE）特性的稳健发光剂是理想的。本文从2,4,5,6-四（咔唑-9-基）-1,3-二氰基苯（4CzIPN）框架派生而来，介绍了两种TADF特征的发光剂，分别为4CzIPN-MO和4CzPhIPN-MO。令人鼓舞的是，连同通过使用甲氧基对4CzIPN的咔唑片段进行修饰，可以观察到与4CzPhIPN-MO一样的意想不到的AIE行为，在咔唑部分和中心苯环之间插入了苯基桥。新颖设计的优点发现4CzPhIPN-MO结构能够减少注入势垒，抑制非辐射衰减并提高固态光致发光（PL）效率。因此，无掺杂OLED在100和1000 cd m ^-2的亮度下表现出色，最大EQE为14.5％，效率极低的下降率分别为3.8％和3.9％，这是最佳EQE值之一迄今为止，未掺杂的溶液处理的TADF OLED的低通性能。这项工作表明，分子拓扑结构的操纵是实现有效且稳定的溶液处理OLED的一种有前途的实用策略。