Open AccessHigh‐Efficiency Solution‐Processable OLEDs by Employing Thermally Activated Delayed Fluorescence Emitters with Multiple Conversion Channels of Triplet Excitons
Author(s) -
Liu Yuchao,
Hua Lei,
Zhao Zhennan,
Ying Shian,
Ren Zhongjie,
Yan Shouke
Publication year - 2021
Publication title -
advanced science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.388
H-Index - 100
ISSN - 2198-3844
DOI - 10.1002/advs.202101326
Subject(s) - exciton , intersystem crossing , oled , photoluminescence , photochemistry , materials science , quantum efficiency , stacking , fluorescence , common emitter , optoelectronics , chemistry , nanotechnology , excited state , singlet state , atomic physics , physics , optics , organic chemistry , quantum mechanics , layer (electronics)
The state‐of‐the‐art luminescent materials are gained widely by utilizing thermally activated delayed fluorescence (TADF) mechanism. However, the feasible molecular designing strategy of fully exploiting triplet excitons to enhance TADF properties is still in demand. Herein, TADF emitters with multiple conversion channels of triplet excitons are designed by concisely halogenating the electron acceptors containing carbonyl moiety. Compared with the chlorinated and brominated analogues, the fluorinated emitter exhibits distinguishing molecular stacking structures, participating in the formation of trimers through integrating CH···F and C═O···H hydrogen bonds together. It is also demonstrated that the multiple channels can be involved synergistically to accelerate the spin‐flip of triplet excitons, and to take charge of the relatively superior reverse intersystem crossing constant rate of 6.20 × 10 5 s –1 , and thus excellent photoluminescence quantum yields over 90% can easily be achieved. Then the solution‐processable organic light emitting diode based on fluorinated emitter can achieve a record‐high external quantum efficiency value of 27.13% and relatively low efficiency roll‐off with remaining 24.74% at 1000 cd m −2 . This result manifests the significance of enhancing photophysical properties through constructing multiple conversion channels of triplets excitons for high‐efficiency TADF emitters and provides a guideline for the future study.