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Molecular Design Approach Managing Molecular Orbital Superposition for High Efficiency without Color Shift in Thermally Activated Delayed Fluorescent Organic Light-Emitting Diodes |
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| Authors: | Dr Mounggon Kim Seong-Jun Yoon Si Hyun Han Ramin Ansari Prof John Kieffer Prof Jun Yeob Lee Prof Jinsang Kim |
| Institution: | 1. Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan, 48109 USA
These authors contributed equally to this work.;2. School of Chemical Engineering, Sungkyunkwan University, 2066, Seobu-ro, Jangan-gu, Suwon, Gyeonggi, 440-746 Korea These authors contributed equally to this work.;3. Department of Chemical Engineering, University of Michigan, Ann Arbor, Michigan, 48109 USA;4. Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan, 48109 USA;5. School of Chemical Engineering, Sungkyunkwan University, 2066, Seobu-ro, Jangan-gu, Suwon, Gyeonggi, 440-746 Korea |
| Abstract: | Molecular design principles of thermally activated delayed fluorescent (TADF) emitters having a high quantum efficiency and a color tuning capability was investigated by synthesizing three TADF emitters with donors at different positions of a benzonitrile acceptor. The position rendering a large overlap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) enhances the quantum efficiency of the TADF emitter. Regarding the orbital overlap, donor attachments at 2- and 6-positions of the benzonitrile were more beneficial than 3- and 5-substitutions. Moreover, an additional attachment of a weak donor at the 4-position further increased the quantum efficiency without decreasing the emission energy. Therefore, the molecular design strategy of substituting strong donors at the positions allowing a large molecular orbital overlap and an extra weak donor is a good approach to achieve both high quantum efficiency and a slightly increased emission energy. |
| Keywords: | electronic structure energy conversion fluorescence OLEDs TADF |