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Highly Efficient Thermally Activated Delayed Fluorescence via J‐Aggregates with Strong Intermolecular Charge Transfer
Author(s) -
Xue Jie,
Liang Qingxin,
Wang Rui,
Hou Jiayue,
Li Wenqiang,
Peng Qian,
Shuai Zhigang,
Qiao Juan
Publication year - 2019
Publication title -
advanced materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.707
H-Index - 527
eISSN - 1521-4095
pISSN - 0935-9648
DOI - 10.1002/adma.201808242
Subject(s) - materials science , intermolecular force , oled , exciton , photoluminescence , acceptor , quantum efficiency , fluorescence , singlet state , optoelectronics , excited state , phosphorescence , photochemistry , band gap , chemical physics , molecule , nanotechnology , atomic physics , optics , chemistry , physics , organic chemistry , layer (electronics) , quantum mechanics , condensed matter physics
The development of high‐efficiency and low‐cost organic emissive materials and devices is intrinsically limited by the energy‐gap law and spin statistics, especially in the near‐infrared (NIR) region. A novel design strategy is reported for realizing highly efficient thermally activated delayed fluorescence (TADF) materials via J‐aggregates with strong intermolecular charge transfer (CT). Two organic donor–acceptor molecules with strong and planar acceptor are designed and synthesized, which can readily form J‐aggregates with strong intermolecular CT in solid states and exhibit wide‐tuning emissions from yellow to NIR. Experimental and theoretical investigations expose that the formation of such J‐aggregates mixes Frenkel excitons and CT excitons, which not only contributes to a fast radiative decay rate and a slow nonradiative decay rate for achieving nearly unity photoluminescence efficiency in solid films, but significantly decreases the energy gap between the lowest singlet and triplet excited states (≈0.3 eV) to induce high‐efficiency TADF even in the NIR region. These organic light‐emitting diodes exhibit external quantum efficiencies of 15.8% for red emission and 14.1% for NIR emission, which represent the best result for NIR organic light‐emitting diodes (OLEDs) based on TADF materials. These findings open a new avenue for the development of high‐efficiency organic emissive materials and devices based on molecular aggregates.