A New Design Strategy for Efficient Thermally Activated Delayed Fluorescence Organic Emitters: From Twisted to Planar Structures.

Abstract
In the traditional molecular design of thermally activated delayed fluorescence (TADF) emitters composed of electron-donor and electron-acceptor moieties, achieving a small singlet-triplet energy gap (ΔEST ) in strongly twisted structures usually translates into a small fluorescence oscillator strength, which can significantly decrease the emission quantum yield and limit efficiency in organic light-emitting diode devices. Here, based on the results of quantum-chemical calculations on TADF emitters composed of carbazole donor and 2,4,6-triphenyl-1,3,5-triazine acceptor moieties, a new strategy is proposed for the molecular design of efficient TADF emitters that combine a small ΔEST with a large fluorescence oscillator strength. Since this strategy goes beyond the traditional framework of structurally twisted, charge-transfer type emitters, importantly, it opens the way for coplanar molecules to be efficient TADF emitters. Here, a new emitter, composed of azatriangulene and diphenyltriazine moieties, is theoretically designed, which is coplanar due to intramolecular H-bonding interactions. The synthesis of this hexamethylazatriangulene-triazine (HMAT-TRZ) emitter and its preliminary photophysical characterizations point to HMAT-TRZ as a potential efficient TADF emitter.

Citation
Chen, X., Tsuchiya, Y., Ishikawa, Y., Zhong, C., Adachi, C., & Brédas, J. (2017). A New Design Strategy for Efficient Thermally Activated Delayed Fluorescence Organic Emitters: From Twisted to Planar Structures. Advanced Materials, 29(46), 1702767. doi:10.1002/adma.201702767

Acknowledgements
X.-K.C., C.Z., and J.-L.B. thank King Abdullah University of Science and Technology (KAUST) for generous research funding as well as the KAUST IT Research Computing Team and the Supercomputing Laboratory for providing continuous assistance as well as computational and storage resources. This work was supported in part by the Exploratory Research for Advanced Technology (ERATO, JPMJER1305) from Japan Science and Technology Agency (JST).

Publisher
Wiley

Journal
Advanced Materials

DOI
10.1002/adma.201702767

PubMed ID
29044726

Additional Links
http://onlinelibrary.wiley.com/doi/10.1002/adma.201702767/abstracthttps://rss.onlinelibrary.wiley.com/doi/am-pdf/10.1002/adma.201702767

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