Chen Jia-Xiong, Xiao Ya-Fang, Wang Kai, Sun Dianming, Fan Xiao-Chun, Zhang Xiang, Zhang Ming, Shi Yi-Zhong, Yu Jia, Geng Feng-Xia, Lee Chun-Sing, Zhang Xiao-Hong
Institute of Functional Nano & Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Soochow University, Suzhou, Jiangsu, 215123, P. R. China.
Center of Super-Diamond and Advanced Films (COSDAF) and Department of Chemistry, City University of Hong Kong, Hong Kong SAR, P. R. China.
Angew Chem Int Ed Engl. 2021 Feb 1;60(5):2478-2484. doi: 10.1002/anie.202012070. Epub 2020 Nov 27.
Developing red thermally activated delayed fluorescence (TADF) emitters for high-performance OLEDs is still facing great challenge. Herein, three red TADF emitters, pDBBPZ-DPXZ, pDTBPZ-DPXZ, and oDTBPZ-DPXZ, are designed and synthesized with same donor-acceptor (D-A) backbone with different peripheral groups attaching on the A moieties. Their lowest triplet states change from locally excited to charge transfer character leading to significantly enhance reverse intersystem crossing process. In particular, oDTBPZ-DPXZ exhibits efficient TADF feature and exciton utilization. It not only achieves an external quantum efficiency (EQE) of 20.1 % in red vacuum-processed OLED, but also realize a high EQE of 18.5 % in a solution-processed OLED, which is among the best results in solution-processed red TADF OLEDs. This work provides an effective strategy for designing red TADF molecules by managing energy level alignments to facilitate the up-conversion process and thus enhance exciton harvesting.
开发用于高性能有机发光二极管（OLED）的红色热激活延迟荧光（TADF）发光体仍面临巨大挑战。在此，设计并合成了三种红色TADF发光体pDBBPZ-DPXZ、pDTBPZ-DPXZ和oDTBPZ-DPXZ，它们具有相同的供体-受体（D-A）骨架，且在受体部分连接有不同的外围基团。它们的最低三重态从局域激发态转变为电荷转移态，从而显著增强了反向系间窜越过程。特别地，oDTBPZ-DPXZ表现出高效的TADF特性和激子利用率。它不仅在红色真空处理OLED中实现了20.1%的外量子效率（EQE），还在溶液处理OLED中实现了18.5%的高EQE，这是溶液处理红色TADF OLED中的最佳结果之一。这项工作通过管理能级排列以促进上转换过程并因此增强激子捕获，为设计红色TADF分子提供了一种有效策略。
