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Selenium Substitution Enhances Reverse Intersystem Crossing in a Delayed Fluorescence Emitter
journal contribution
posted on 2020-03-05, 14:20 authored by Bluebell
H. Drummond, Gabrielle C. Hoover, Alexander J. Gillett, Naoya Aizawa, William K. Myers, Bryony T. McAllister, Saul T. E. Jones, Yong-Jin Pu, Dan Credgington, Dwight S. SeferosOrganic emitters
exhibiting delayed fluorescence (DF) are promising
luminescent materials for next-generation organic light-emitting diodes
(OLEDs). Faster intersystem crossing rates and shorter emission lifetimes
can be achieved in luminescent molecules through the incorporation
of heavy atoms, which enhance spin–orbit coupling and promote
intersystem crossing between singlet and triplet states. DF molecules
often contain a sulfur atom, and reports of selenium-containing DF
OLEDs also exist. However, the literature lacks a direct exploration
of the effect of spin–orbit coupling on reverse intersystem
crossing in a delayed fluorescence emitter by the substitution of
selenium for sulfur. Here we show that substitution of selenium for
sulfur in a modified thioxanthenone-triphenylamine analogue increases
the rate of forward intersystem crossing by a factor of over 250 and
the rate of reverse intersystem by a factor of 22. We attribute the
increased rates to enhanced spin–orbit coupling from heavy
atom substitution, and computational and electron spin resonance studies
support this. This work provides an insight into future molecular
design strategies for heavy-atom-containing, DF emitters.
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factorDelayed Fluorescence Emitter Organic emittersthioxanthenone-triphenylamine analogue increasesSelenium Substitution Enhancesatom substitutionresonance studies supportemission lifetimesDF emittersdesign strategiesfluorescence emitterlight-emitting diodesselenium-containing DF OLEDssulfur atomDF moleculesintersystemtriplet states
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