Cascade Effect of a Dimerized Thermally Activated Delayed Fluorescence Dendrimer

Abstract Thermally activated delayed fluorescence (TADF) emitters with a high horizontal orientation are highly essential for improving the external quantum efficiency (EQE) of organic light‐emitting diodes; however, pivotal molecular design strategies to improve the horizontal orientation of soluti...

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Published in:Angewandte Chemie International Edition 2024-09, p.e202412720
Main Authors: Zhao, Guimin, Lv, Shuai, Lou, Yuheng, Zhang, Yuewei, Zhang, Dongdong, Jiang, Wei, Sun, Yueming, Duan, Lian
Format: Article
Language:English
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Summary:Abstract Thermally activated delayed fluorescence (TADF) emitters with a high horizontal orientation are highly essential for improving the external quantum efficiency (EQE) of organic light‐emitting diodes; however, pivotal molecular design strategies to improve the horizontal orientation of solution‐processable TADF emitters are still scarce and challenging. Herein, a phenyl bridge is adopted to connect the double TADF units, and generate a dimerized TADF dendrimer, D4CzBNPh‐SF. Compared to its counterpart with a single TADF unit, the proof‐of‐the‐concept molecule not only exhibits an improved horizontal dipole ratio (78 %) due to the π‐delocalization‐induced extended molecular conjugation, but also displays a faster reversed intersystem crossing rate constant (6.08×10 6 s −1 ) and a high photoluminescence quantum yield of 95 % in neat film. Consequently, the non‐doped solution‐processed device with D4CzBNPh‐SF as the emitter achieves an ultra‐high maximum EQE of 32.6 %, which remains at 26.6 % under a luminance of 1000 cd/m 2 . Furthermore, when using D4CzBNPh‐SF as a sensitizer, the TADF‐sensitized fluorescence device exhibits a high maximum EQE of 30.7 % at a luminance of 575 cd/m 2 and a full width at half maximum of 36 nm.
ISSN:1433-7851
1521-3773
1521-3773
DOI:10.1002/anie.202412720