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7535616 
Journal Article 
Molecular Configuration Fixation with C-H center dot center dot center dot F Hydrogen Bonding for Thermally Activated Delayed Fluorescence Acceleration 
Yuan, W; Yang, H; Duan, C; Cao, X; Zhang, J; Xu, Hui; Sun, N; Tao, Y; Huang, Wei; , 
2020 
CELL PRESS 
CAMBRIDGE 
1998-2008 
WOS:000558679600015 
The conflict between improving reverse intersystem crossing (RISC) and singlet radiation is one of the key fundamental issues for thermally activated delayed fluorescence (TADF) materials. Here, we demonstrate that the excited-state structural relaxation can be effectively suppressed through fixing the molecular configuration with intramolecular C-H center dot center dot center dot F hydrogen bonds. The resulted TADF emitter 7CzFDCF(3)DPh reveals the nearly identical ground state, the first singlet (S-1) and triplet (T-1) excited-state configurations. Therefore, the singlet-triplet energy gap is reduced to <0.06 eV, establishing the multiple RISC channels through either electronic or vibrational couplings. 7CzFDCF(3)DPh reveals a state-of-the-art RISC rate constant (k(RISC)) of similar to 10(6) s(-1), accompanied by the doubled RISC efficiency ((phi(RISC)) as high as 97%. The dramatically accelerated TADF renders the photoluminescence and electroluminescence quantum efficiencies more than 90% and 20% for 7CzFDCF(3)DPh. These results manifest the significance of the configuration fixation for improving TADF performance.