Donor–σ–Acceptor Motifs: Thermally Activated Delayed Fluorescence Emitters with Dual Upconversion

• Published in: Angewandte Chemie International Edition Vol. 56; no. 52; pp. 16536 - 16540
• Main Authors: Geng, Yan, D'Aleo, Anthony, Inada, Ko, Cui, Lin‐Song, Kim, Jong Uk, Nakanotani, Hajime, Adachi, Chihaya
• Format: Journal Article
• Language: English
• Published: WEINHEIM Wiley 22.12.2017; Wiley Subscription Services, Inc; Wiley-VCH Verlag
• Edition: International ed. in English
• Subjects: Charge transfer; Chemical Sciences; Chemistry; Chemistry, Multidisciplinary; delayed fluorescence; donor–acceptor molecules; Emitters; Fluorescence; hyperconjugation; Material chemistry; organic light-emitting diodes; Photoluminescence; Photons; Physical Sciences; Quantum efficiency; Science & Technology; TADF lifetime; Toluene; Triplet state; Upconversion; DESIGN; donor-acceptor molecules; TADF lifetime; STRATEGY; COMPLEXES; OLEDS; hyperconjugation; GREEN; organic light-emitting diodes; LIGHT-EMITTING-DIODES; EXTERNAL QUANTUM EFFICIENCY; delayed fluorescence; DEVICES; CHARGE-TRANSFER
• ISSN: 1433-7851; 1521-3773; 1521-3773
• DOI: 10.1002/anie.201708876

A family of organic emitters with a donor–σ–acceptor (D‐σ‐A) motif is presented. Owing to the weakly coupled D‐σ‐A intramolecular charge‐transfer state, a transition from the localized excited triplet state (3LE) and charge‐transfer triplet state (3CT) to the charge‐transfer singlet state (1CT) occurred with a small activation energy and high photoluminescence quantum efficiency. Two thermally activated delayed fluorescence (TADF) components were identified, one of which has a very short lifetime of 200–400 ns and the other a longer TADF lifetime of the order of microseconds. In particular, the two D‐σ‐A materials presented strong blue emission with TADF properties in toluene. These results will shed light on the molecular design of new TADF emitters with short delayed lifetimes. Avoid long delays: A novel molecular design for thermally activated delayed fluorescence (TADF) emitters based on a donor–σ–acceptor motif led to short TADF decay lifetimes of less than 400 ns. Since shorter delayed lifetimes in TADF emitters are highly beneficial for device performance, this design strategy is expected to provide an effective approach to advanced TADF materials.