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Intramolecular exciplex-typed molecule based on a stereoscopic V-shaped aromatic macrocycle and investigation of host-dependence of exciton utilization.
- Source :
-
Chemical Engineering Journal . Dec2022:Part 3, Vol. 450, pN.PAG-N.PAG. 1p. - Publication Year :
- 2022
-
Abstract
- • A stereoscopic aromatic macrocycle was used to form a new-type TSCT-TADF emitter. • The rigid electron-deficient macrocycle clips the triphenylamine unit. • OC2A2T-TPA shows an extremely small ΔE ST of 18 meV. • OC2A2T-TPA behaves like an intramolecular exciplex. • Sensitizing the high-lying LE states is required to realize high exciton utilization. Through-space charge transfer (TSCT) has been increasingly utilized for the design of efficient thermally activated delayed fluorescence (TADF) emitters. TSCT molecular skeletons with spatially and electronically confined D/A subunits can provide a small ΔE ST , and also ease for fine control of CT properties within a single molecule. However so far TSCT-TADF molecules have not been fully investigated. Herein, we report a new ortho -position molecular pattern for TSCT-TADF design, using a stereoscopic V-shaped aromatic macrocycle of electron-deficient oxacalix[2]arene[2]triazine to "clip" the electron-rich triphenylamine unit. The new emitter OC2A2T-TPA exhibits a small ΔE ST of 18 meV, and the OLED device that uses high-energy-level host DPEPO realizes the first-time electroluminescence application of OC2A2T-type macrocyclic compounds by achieving an impressive external quantum efficiency (EQE) of 14.6 %. Further host-dependence investigation reveals that OC2A2T-TPA actually behaves like an intramolecular exciplex, exhibiting high exciton utilization once its high-lying locally excited (LE) states on D/A could be sensitized first in the case of DPEPO host, otherwise low exciton utilization in the case of lower-energy-level mCP host. This work opens a way to enrich TSCT-TADF design and clarifies the importance to involve the high-lying LE states in the energy transfer routes for high-efficiency intramolecular-exciplex molecules. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 13858947
- Volume :
- 450
- Database :
- Academic Search Index
- Journal :
- Chemical Engineering Journal
- Publication Type :
- Academic Journal
- Accession number :
- 159075390
- Full Text :
- https://doi.org/10.1016/j.cej.2022.138174