Cheng Ying-Chun, Tang Xun, Walia Rajat, Zhang Tong-Yuan, Fan Xiao-Chun, Yu Jia, Wang Kai, Adachi Chihaya, Chen Xian-Kai, Zhang Xiao-Hong
Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University, Suzhou, Jiangsu, 215123, P. R. China.
Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, 15 Fukuoka, Fukuoka, 819-0395, Japan.
Adv Mater. 2025 Aug;37(32):e2500010. doi: 10.1002/adma.202500010. Epub 2025 May 30.
Solution-processable organic light-emitting diodes (OLEDs) have attracted much attention from academia and industry because of their advantages such as low production cost and suitability for large-scale production. However, solution-processable deep-blue OLEDs that simultaneously have high efficiencies and satisfy the BT.2020 standard remain still a great challenge. To address this issue, here a tetraboron multiresonance thermally activated delayed fluorescence (MR-TADF) emitter, tBO-4B, embedded with two soluble 2,12-di-tert-butyl-5,9-dioxa-13b-boranaphtho[3,2,1-de]anthracene groups is designed and synthesized with a linearly fully fused acceptor-donor-acceptor-type molecular structure. tBO-4B not only achieves an ultranarrow full width at half maximum of 12 nm but also has a negligibly small singlet-triplet energy gap and large spin‒orbit coupling, eventually leading to very fast reverse intersystem crossing rate (4.23 × 10 s). The sensitizer-free solution-processed OLED exploiting tBO-4B as the emitter achieves an ultrahigh maximum external quantum efficiency (EQE) of 30.3%, with Commission Internationale de l'Éclairage (CIE) coordinates of (0.147, 0.042) meeting the BT.2020 blue standard. In addition, the corresponding sensitizer-free vacuum-processed deep-blue devices also exhibit an impressive EQE of 39.6% and mild efficiency roll-off with CIE coordinates of (0.147, 0.043). This work will facilitate the development of high-efficiency ultrapure deep-blue MR-TADF materials for solution- and vacuum-processed OLEDs.
溶液可加工有机发光二极管（OLED）因其生产成本低和适合大规模生产等优点而备受学术界和工业界关注。然而，同时具有高效率并满足BT.2020标准的溶液可加工深蓝色OLED仍然是一个巨大挑战。为解决这一问题，本文设计并合成了一种嵌入两个可溶性2,12-二叔丁基-5,9-二氧杂-13b-硼萘并[3,2,1-de]蒽基团的四硼多共振热激活延迟荧光（MR-TADF）发射体tBO-4B，其具有线性全稠合受体-供体-受体型分子结构。tBO-4B不仅实现了12nm的超窄半高宽，而且单重态-三重态能隙极小，自旋-轨道耦合大，最终导致非常快的反向系间窜越速率（4.23×10¹⁰ s⁻¹）。以tBO-4B作为发射体的无敏化剂溶液加工OLED实现了30.3%的超高最大外量子效率（EQE），国际照明委员会（CIE）坐标为（0.147, 0.042），符合BT.2020蓝色标准。此外，相应的无敏化剂真空加工深蓝色器件也表现出令人印象深刻的39.6%的EQE和温和的效率滚降，CIE坐标为（0.147, 0.043）。这项工作将促进用于溶液和真空加工OLED的高效超纯深蓝色MR-TADF材料的开发。
