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 now.Herein, 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.
超敏荧光有机发光二极管(TSF-OLEDs)在实现高效率、低效率滚降和良好色纯度方面显示出巨大的潜力.迄今为止,优秀的TSF-OLEDs器件鲜有报道.本文提出了一种新型受体分子的设计策略,通过构建三嗪并三氮唑(TAZTRZ)受体单元,设计合成高效热活化延迟荧光(TADF)材料以获得高性能的TSF-OLEDs器件.通过将三嗪(TRZ)和三氮唑(TAZ)稠合,可以增强受体的吸电子能力,从而减小TADF材料的单-三线态能隙(△E_(ST)).同时,受体-苯桥的连接方式由六元环的TRZ-苯桥(6:6)连接转变为五元环TAZ-苯桥(5:6)连接,可以在降低△E_(ST)的同时,一定程度补偿振子强度(f)的降低,从而实现较小的△E_(ST)与较高f之间的平衡.最后,基于TAZTRZ受体的TADF材料实现了目前综合性能最为优异的TSF-OLEDs器件,其启亮电压仅为2.1 V,外量子效率(EQE_(max))高达23.7%,并且展现出具有极小的效率滚降(EQE_(1000)=23.2%;EQE_(5000)=20.6%)和极高的功率效率(82.1 lm W^(-1)).
基金
This work was supported by the National Natural Science Foundation of China(21432005)
the Fundamental Research Funds for the Central Universities and the Comprehensive Training Platform Specialized Laboratory,College of Chemistry,Sichuan University。
