Red/Near‐Infrared Thermally Activated Delayed Fluorescence OLEDs with Near 100 % Internal Quantum Efficiency

• Published in: Angewandte Chemie International Edition Vol. 58; no. 41; pp. 14660 - 14665
• Main Authors: Chen, Jia‐Xiong, Tao, Wen‐Wen, Chen, Wen‐Cheng, Xiao, Ya‐Fang, Wang, Kai, Cao, Chen, Yu, Jia, Li, Shengliang, Geng, Feng‐Xia, Adachi, Chihaya, Lee, Chun‐Sing, Zhang, Xiao‐Hong
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 07-10-2019
• Edition: International ed. in English
• Subjects: Chemical synthesis; Diodes; Efficiency; Emission; Emitters; Energy dissipation; Energy loss; Fluorescence; molecular design; OLEDs; Organic light emitting diodes; Photoluminescence; Photons; Pyridines; Quantum efficiency; red/near-IR emission; rigid segments; thermally activated delayed fluorescence; rigid segments; thermally activated delayed fluorescence; OLEDs; molecular design; red/near-IR emission
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.201906575

Developing red thermally activated delayed fluorescence (TADF) emitters, attainable for both high‐efficient red organic light‐emitting diodes (OLEDs) and non‐doped deep red/near‐infrared (NIR) OLEDs, is challenging. Now, two red emitters, BPPZ‐PXZ and mDPBPZ‐PXZ, with twisted donor–acceptor structures were designed and synthesized to study molecular design strategies of high‐efficiency red TADF emitters. BPPZ‐PXZ employs the strictest molecular restrictions to suppress energy loss and realizes red emission with a photoluminescence quantum yield (ΦPL) of 100±0.8 % and external quantum efficiency (EQE) of 25.2 % in a doped OLED. Its non‐doped OLED has an EQE of 2.5 % owing to unavoidable intermolecular π–π interactions. mDPBPZ‐PXZ releases two pyridine substituents from its fused acceptor moiety. Although mDPBPZ‐PXZ realizes a lower EQE of 21.7 % in the doped OLED, its non‐doped device shows a superior EQE of 5.2 % with a deep red/NIR emission at peak of 680 nm.
Two red emitters, BPPZ‐PXZ and mDPBPZ‐PXZ, with twisted donor–acceptor structures were designed and synthesized to study molecular design strategies of high‐efficiency red TADF emitters. BPPZ‐PXZ employs the strictest molecular restrictions to suppress energy loss and realizes red emission with a photoluminescence quantum yield (ΦPL) of 100±0.8 % and external quantum efficiency (EQE) of 25.2 % in a doped OLED.