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

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

doi:10.1038/s41467-023-38086-4

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

Nat Commun. 2023 Apr 26;14(1):2394. doi: 10.1038/s41467-023-38086-4.

Authors

Guoyun Meng¹, Hengyi Dai¹, Qi Wang¹, Jianping Zhou¹, Tianjiao Fan¹, Xuan Zeng¹, Xiang Wang¹, Yuewei Zhang^{1

2}, Dezhi Yang³, Dongge Ma³, Dongdong Zhang^{4

5}, Lian Duan^{6

7}

Affiliations

¹ Key Laboratory of Organic Optoelectronics, Department of Chemistry, Tsinghua University, Beijing, 100084, P. R. China.
² Laboratory of Flexible Electronics Technology, Tsinghua University, Beijing, 100084, P. R. China.
³ Institute of Polymer Optoelectronic Materials and Devices State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou, 510640, P. R. China.
⁴ Key Laboratory of Organic Optoelectronics, Department of Chemistry, Tsinghua University, Beijing, 100084, P. R. China. ddzhang@mail.tsinghua.edu.cn.
⁵ Laboratory of Flexible Electronics Technology, Tsinghua University, Beijing, 100084, P. R. China. ddzhang@mail.tsinghua.edu.cn.
⁶ Key Laboratory of Organic Optoelectronics, Department of Chemistry, Tsinghua University, Beijing, 100084, P. R. China. duanl@mail.tsinghua.edu.cn.
⁷ Laboratory of Flexible Electronics Technology, Tsinghua University, Beijing, 100084, P. R. China. duanl@mail.tsinghua.edu.cn.

Abstract

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 (ΔE_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 ΔE_ST and a large f. Moreover, the incorporation of dual equivalent multiresonance-acceptors is found to double the f value without affecting the ΔE_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 >10⁶ s^-1 are simultaneously obtained in one emitter, leading to a short delayed-lifetime of ~0.88 μs. 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.