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Thermally Activated Delayed Fluorescence in an Organic Cocrystal: Narrowing the Singlet–Triplet Energy Gap via Charge Transfer
Author(s) -
Sun Lingjie,
Hua Weijie,
Liu Yang,
Tian Guangjun,
Chen Mingxi,
Chen Mingxing,
Yang Fangxu,
Wang Shufeng,
Zhang Xiaotao,
Luo Yi,
Hu Wenping
Publication year - 2019
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201904427
Subject(s) - cocrystal , intersystem crossing , photoluminescence , singlet state , exciton , photochemistry , intermolecular force , triplet state , spectroscopy , chemistry , band gap , organic semiconductor , materials science , fluorescence , optoelectronics , atomic physics , excited state , physics , molecule , optics , condensed matter physics , organic chemistry , hydrogen bond , quantum mechanics
Harvesting non‐emissive spin‐triplet charge‐transfer (CT) excitons of organic semiconductors is fundamentally important for increasing the operation efficiency of future devices. Here we observe thermally activated delayed fluorescence (TADF) in a 1:2 CT cocrystal of trans ‐1,2‐diphenylethylene (TSB) and 1,2,4,5‐tetracyanobenzene (TCNB). This cocrystal system is characterized by absorption spectroscopy, variable‐temperature steady‐state and time‐resolved photoluminescence spectroscopy, single‐crystal X‐ray diffraction, and first‐principles calculations. These data reveal that intermolecular CT in cocrystal narrows the singlet–triplet energy gap and therefore facilitates reverse intersystem crossing (RISC) for TADF. These findings open up a new way for the future design and development of novel TADF materials.