High-efficiency and stable short-delayed fluorescence emitters with hybrid long- and short-range charge-transfer excitations

作者：Meng, Guoyun; Dai, Hengyi; Wang, Qi; Zhou, Jianping; Fan, Tianjiao; Zeng, Xuan; Wang, Xiang; Zhang, Yuewei; Yang, Dezhi; Ma, Dongge; Zhang, Dongdong^*; Duan, Lian^*

来源：Nature Communications, 2023, 14(1): 2394.

DOI：10.1038/s41467-023-38086-4

• LIGHT-EMITTING-DIODES

To possess a small singlet-triplet energy gap and a large oscillator strength simultaneously is critical for efficient thermally activated delayed fluorescent emitters. Here, the authors attach an multiresonance-acceptor onto a sterically-uncrowded donor for realizing a device efficiency of 40.4%. @@@ The pursuit of ideal short-delayed thermally activated delayed fluorescence (TADF) emitters is hampered by the mutual exclusion of a small singlet-triplet energy gap (Delta E-ST) and a large oscillator strength (f). Here, by attaching an multiresonance-acceptor onto a sterically-uncrowded donor, we report TADF emitters bearing hybrid electronic excitations with a main donor-to-acceptor long-range (LR) and an auxiliary bridge-phenyl short-range (SR) charge-transfer characters, balancing a small Delta E-ST and a large f. Moreover, the incorporation of dual equivalent multiresonance-acceptors is found to double the f value without affecting the Delta E-ST. A large radiative decay rate over an order of magnitude higher than the intersystem crossing (ISC) rate, and a decent reverse ISC rate of >10(6) s(-1) are simultaneously obtained in one emitter, leading to a short delayed-lifetime of similar to 0.88 mu s. The corresponding organic light-emitting diode exhibits a record-high maximum external quantum efficiency of 40.4% with alleviated efficiency roll-off and extended lifetime.

• 单位
  清华大学