New electron-donating segment to develop thermally activated delayed fluorescence emitters for efficient solution-processed non-doped organic light-emitting diodes

• Published in: Chinese chemical letters 2022-02, Vol.33 (2), p.1110-1115
• Main Authors: Zhang, Ming, Dai, Gaole, Zheng, Caijun, Wang, Kai, Shi, Yizhong, Fan, Xiaochun, Lin, Hui, Tao, Silu, Zhang, Xiaohong
• Format: Article
• Language: English
• Subjects: Electron-donating segment; Non-doped emitter; Organic light-emitting diode; Solution process; Thermally activated delayed fluorescence
• ISSN: 1001-8417; 1878-5964
• DOI: 10.1016/j.cclet.2021.08.064

Thermally activated delayed fluorescent (TADF) materials capable of efficient solution-processed non-doped organic light-emitting diodes (OLEDs) are of important and practical significance for further development of OLEDs. In this work, a new electron-donating segment, 2,7-di(9H-carbazol-9-yl)-9,9-dimethyl-9,10-dihydroacridine (2Cz-DMAC), was designed to develop solution-processable non-doped TADF emitters. 2Cz-DMAC can not only simultaneously increase the solubility of compounds and suppress harmful aggregation-caused quenching, but also efficiently broaden the delocalization of the highest occupied molecular orbital and promote the reverse intersystem crossing process. Three new TADF emitters, 2-(2,7-di(9H-carbazol-9-yl)-9,9-dimethylacridin-10(9H)-yl)dibenzo[b,d]thiophene 5,5-dioxide (2Cz-DMAC-BTB), 2-(2,7-di(9H-carbazol-9-yl)-9,9-dimethylacridin-10(9H)-yl)-9H-thioxanthen-9-one (2Cz-DMAC-TXO), 2-(2,7-di(9H-carbazol-9-yl)-9,9-dimethylacridin-10(9H)-yl)thianthrene 5,5,10,10-tetraoxide (2Cz-DMAC-TTR), were developed by using 2Cz-DMAC segment as the electron-donor. As anticipated, the solution-processed non-doped OLEDs employing 2Cz-DMAC-BTB, 2Cz-DMAC-TXO and 2Cz-DMAC-TTR as the emitters respectively exhibited green, orange and red emissions with maximum external quantum efficiencies of 14.0%, 6.6% and 2.9%. These results successfully demonstrate the feasibility and convenience of developing efficient solution-processable non-doped TADF emitters based on 2Cz-DMAC segment. [Display omitted] A new electron-donating segment 2Cz-DMAC was proposed to develop solution-processable non-doped TADF emitters. Accordingly, 2Cz-DMAC-BTB, 2Cz-DMAC-TXO and 2Cz-DMAC-TTR were designed and synthesized, realizing green, orange and red emissions with maximum EQEs of 14.0%, 6.6% and 2.9% in the solution-processed non-doped OLEDs.