Novel D-D′-A structure thermally activated delayed fluorescence emitters realizing over 20% external quantum efficiencies in both evaporation- and solution-processed organic light-emitting diodes

• Published in: Organic electronics 2021-12, Vol.99, p.106312, Article 106312
• Main Authors: Zhang, Ming, Dai, Gao-Le, Zheng, Cai-Jun, Wang, Kai, Shi, Yi-Zhong, Fan, Xiao-Chun, Lin, Hui, Tao, Si-Lu, Zhang, Xiao-Hong
• Format: Article
• Language: English
• Subjects: Intramolecular and intermolecular charge-transfer transitions; Organic light-emitting diode; Solution process; Thermally activated delayed fluorescence
• ISSN: 1566-1199; 1878-5530
• DOI: 10.1016/j.orgel.2021.106312

Thermally activated delayed fluorescence (TADF) emitters have only realized limited performance in solution-processed organic light-emitting diodes (OLEDs) comparing to in evaporation-processed OLEDs. To address this issue, a novel D-D′-A structure, where A is the electron-accepting group, D is the primary electron-donating group and D′ is the secondary electron-donating group, was proposed to develop efficient solution-processable TADF emitters in this work. As the intermediate D′ spacer weakens the direct intramolecular interaction between D and A groups, D-D′-A structure molecules simultaneously possess intramolecular and intermolecular charge-transfer transition channels, suppressing the aggregation-caused quenching induced by solution process. Accordingly, a novel TADF emitter 2-(3,6-bis(9,9-dimethylacridin-10(9H)-yl)-9H-carbazol-9-yl)thianthrene 5,5,10,10-tetraoxide (DMAC-Cz-TTR) was designed and synthesized. In the optimized evaporation- and solution-processed OLEDs, DMAC-Cz-TTR successfully realized similar maximum external quantum efficiencies (EQEs) of 21.1% and 20.6%, respectively. To the best of our knowledge, this is the first TADF emitter realizing nearly equal performance in both evaporation- and solution-processed OLEDs with over 20% EQEs. The outstanding performance of DMAC-Cz-TTR successfully demonstrates the feasibility of the D-D′-A structure to develop efficient solution-processable TADF emitters. [Display omitted] •A novel D-D′-A structure was proposed to develop efficient solution-processed TADF emitters.•A new TADF emitter DMAC-Cz-TTR was developed accordingly with intra- and inter-CT transition channels simultaneously.•In the evaporation- and solution-processed OLEDs, DMAC-Cz-TTR realized maximum EQEs of 21.1% and 20.6%, respectively.