Modulation of π-linkers in asymmetric thermally activated delayed fluorescence molecules enabling high performance OLEDs
Modulation of π-linkers in asymmetric thermally activated delayed fluorescence molecules enabling high performance OLEDs
复制标题
调节不对称热激活延迟荧光分子中的 pi 连接体可实现高性能 OLED
DOI：
10.1039/c9tc06608j
复制
发表时间：
2020-03-21
影响因子：
6.4
通讯作者：
Chi, Zhenguo
中科院分区：
文献类型：
--
作者：
Wei, Weichun;Yang, Zhan;Chi, Zhenguo
芳香族π桥（称为π-连接体）用于连接不对称热激活延迟荧光（TADF）发射体中的多个D和A基团，其作用仍然是开发高效有机发光二极管（OLED）的关键问题。在本工作中，基于我们先前的具有电子给体咔唑（D）和吩噻嗪（D '）的不对称TADF发射体（SCP），我们在SCP的两侧引入不同数目的苯环作为π-连接体，导致具有不同共轭水平的四种D-A-D ' TADF发射体（PCz，2 PCz，PSz和2 PSz）。实验和理论结果表明，π-连接体的距离有显着的影响，激发态的调节，从而光电性能。相比之下，具有较短的π-连接体的TADF发射体（PCz和PSz）表现出较高的光致发光量子产率，这是由于有效抑制了基态和激发态之间的构象变化，因此实现了具有20%至30%范围内的外部量子效率（EQE）的较高器件性能。这项工作提供了一个洞察分子设计和非对称TADF发射器的光电性能之间的关系。
The role of aromatic pi bridges (called pi-linkers), which are used to connect multiple D and A groups in asymmetric thermally activated delayed fluorescence (TADF) emitters, remains a critical issue for the development of high-efficiency organic light-emitting diodes (OLEDs). In this work, based on our previous asymmetric TADF emitter (SCP) with electron donors carbazole (D) and phenothiazine (D '), we introduced different numbers of phenyl rings as pi-linkers on both sides of SCP, leading to four D-A-D ' TADF emitters (PCz, 2PCz, PSz, and 2PSz) with different levels of conjugation. Experimental and theoretical results reveal that the pi-linker distance has a significant effect on excited state regulation and thereby the optoelectronic properties. In comparison, the TADF emitters (PCz, and PSz) with shorter pi-linkers exhibit higher photoluminescence quantum yields, due to effective suppression of conformation changes between ground state and excited state, and consequently higher device performance with external quantum efficiencies (EQEs) ranging from 20% to 30% achieved. This work provides an insight into the relationship between molecular design and optoelectronic properties of asymmetric TADF emitters.