1. Thermally Activated Delayed Fluorescence Mediated through the Upper Triplet State Manifold in Non-Charge-Transfer Star-Shaped Triphenylamine–Carbazole Molecules
- Author
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Piotr Pander, Marilia J. Caldas, Radoslaw Motyka, Tales J. da Silva, Pawel Zassowski, Marc K. Etherington, Daniele Varsano, Andrew P. Monkman, and Przemyslaw Data
- Subjects
Materials science ,Oscillator strength ,F100 ,F200 ,02 engineering and technology ,010402 general chemistry ,Triphenylamine ,Photochemistry ,01 natural sciences ,chemistry.chemical_compound ,Charge transfer ,Physical and Theoretical Chemistry ,Triplet state ,Carbazole ,021001 nanoscience & nanotechnology ,Internal conversion (chemistry) ,Fluorescence ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,General Energy ,Intersystem crossing ,chemistry ,Electronic excitations ,Excited state ,fluorescence ,0210 nano-technology - Abstract
Thermally activated delayed fluorescence has been found in a group of tricarbazolylamines that are purely electron-donating, non-charge-transfer (CT) molecules. We show that the reverse intersystem crossing step in these materials is mediated through upper triplet states. Reverse internal conversion is shown to be the thermally activated mechanism behind the triplet harvesting mechanism. The strongly mixed n−π*/π–π* character of the lowest energy optical transitions retains high oscillator strength and gives rise to high ΦPL. Organic light-emitting diode devices using these materials were fabricated to show very narrow (full width at half-maximum = 38–41 nm) electroluminescence spectra, clearly demonstrating the excitonic nature of the excited states. This new combination of physicochemical properties of a non-CT molecule yields thermally activated delayed fluorescence, but via a different, physical mechanism, reverse internal conversion delayed fluorescence.
- Published
- 2018