摘要：thermally activated delayed fluorescence(TADF) sensitized fluorescent organic light-emitting diodes(TSF-OLEDs) have shown great potential for the realization of high efficiency with low efficiency rolloff and good color purity. However, the superior examples of TSF-OLEDs are still limited up to ***, a trade-off strategy is presented for designing efficient TADF materials and achieving highperformance TSF-OLEDs via the construction of a new type of triazolotriazine(TAZTRZ) acceptor. The enhanced electron-withdrawing ability of TAZTRZ acceptor, fused by triazine(TRZ) and triazole(TAZ)together, enables TADF luminogens with small singlet-triplet energy gap(ΔE_(ST)) values. Meanwhile, the increased planarity from the TRZ-phenyl linkage(6:6 system) to the TAZ-phenyl linkage(5:6 system)can compensate the decrease of oscillator strength(f) while lowing ΔE_(ST), thus achieving a trade-off between small ΔE_(ST) and high f. As a result, the related TSF-OLED achieved an extremely low turn-on voltage of 2.1 V, an outstanding maximum external quantum efficiency(EQEmax) of 23.7% with small efficiency roll-off(EQE1000 of 23.2%;EQE5000 of 20.6%) and an impressively high maximum power efficiency of 82.1 lm W^(-1), which represents the state-of-the-art performance for yellow TSF-OLEDs.

摘要：An optimized compound 9-(9,9-dimethylacridin-10(9 H)-yl)-6 H-benzo[c]ch-romen-6-one(MAB) was designed and synthesized based on our previously reported TADF emitter 6-(9,9-dimethylacridin-10(9 H)-yl)-3-methyl-1 H-isochromen-1-one(MAC) to further improve the performance of thermally activated delayed fluorescence(TADF)emitters. With the additional phenyl in coumarin-contained plane, MAB possesses an extended distribution of the lowest unoccupied molecular orbitals(LUMO), and thus realizes reduced electron exchange between the frontier molecular orbitals and a stretched molecular dipole moment compared with MAC. MAB based organic light-emitting diode(OLED)exhibits a remarkable maximum external quantum efficiency(EQE) of 21.7%, which is much better than the maximum EQE of MAC-based OLED with a value of 12.8%. Our work proves that extending the distribution of LUMO is a simple but effective method to improve the efficiency of TADF emitter.

摘要：How to control the dipole orientation of organic emitters is a challenge in the field of organic light-emitting diodes(OLEDs).Herein,a linear thermally activated delayed fluorescence(TADF)molecule,PhNAI-PMSBA,bearing a 1,8-naphthalimide-acridine framework was designed by a doublesite long-axis extension strategy to actively control the dipole *** horizontal ratio of emitting dipole orientation of PhNAI-PMSBA reaches 95%,substantially higher than that of isotropic emitters(67%).This unique feature is associated with the intrinsically horizontal molecular orientation of PhNAI-PMSBA and the good agreement between its transition dipole moment direction and molecular long *** PhNAI-PMSBA-based OLED achieves an ultrahigh optical outcoupling efficiency of 43.2%and thus affords one of the highest red electroluminescence with an external quantum efficiency of 22.3%and the Commission International de l’Eclairage 1931 coordinates at around(0.60,0.40).

摘要：基于空间电荷转移(TSCT)的热激活延迟荧光(TADF)材料因其可同时实现小的单重态-三重态分裂能(ΔEST)和快速的辐射速率(kf)而受到广泛关注,但对这类材料的合理设计仍面临挑战.本工作使用极化连续介质模型和量子力学与分子力学结合的方法,对咔唑基TSCTTADF材料在液相和固相中的光物理性质进行了理论研究,阐明其实验性能的差异并揭示分子设计规则.研究表明给体(D)、受体(A)单元平面度逐渐增强的分子表现出D和A单元之间的距离减小、分子内相互作用增强,导致其在固相中有利的辐射过程;并且A单元平面度的增强显著限制了分子的拉伸和旋转振动,减少了非辐射损失,有助于分子性能的提高.此外,这类分子的前线轨道分布显示出明显的分离,有利于实现较小的ΔEST.这些新的理论认识可以对TSCT-TADF材料的结构-性能关系提供深入的光物理见解,为设计和探索高性能TADF材料提供有效策略.