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Abstract
Thermally activated delayed fluorescence (TADF) relies on a small energy gap between the emissive singlet and the nonemissive triplet state, obtained by reducing the wave function overlap between donor and acceptor moieties. Efficient emission, however, requires maintaining a good oscillator strength, which is itself based on sufficient overlap of the wave functions between donor and acceptor moieties. We demonstrate an approach to subtly fine-tune the required wave function overlap by employing donor dendrons of changing functionality. We use a carbazolyl-phthalonitrile based donor–acceptor core (2CzPN) as a reference emitter and progressively localize the hole density through substitution at the 3,6-positions of the carbazole donors (Cz) with further carbazole, (4-tert-butylphenyl)amine (tBuDPA), and phenoxazine (PXZ). Using detailed photoluminescence studies, complemented with density functional theory (DFT) calculations, we show that this approach permits a gradual decrease of the singlet–triplet gap, ΔEST, from 300 to around 10 meV in toluene, yet we also demonstrate why a small ΔEST alone is not enough. While sufficient oscillator strength is maintained with the Cz- and tBuDPA-based donor dendrons, this is not the case for the PXZ-based donor dendron, where the wave function overlap is reduced too strongly. Overall, we find the donor dendron extension approach allows successful fine-tuning of the emitter photoluminescence properties.
Original language | English |
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Pages (from-to) | 552-562 |
Number of pages | 11 |
Journal | The Journal of Physical Chemistry. B, Condensed matter, materials, surfaces, interfaces & biophysical |
Volume | 126 |
Issue number | 2 |
DOIs | |
Publication status | Published - 20 Jan 2022 |
Funding
This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement no. 812872 (TADFlife). S.B. acknowledges support from the German Science Foundation (392306670/HU2362). The St Andrews team would also like to thank the Leverhulme Trust (RPG-2016-047) and EPSRC (EP/P010482/1) for financial support. Computational resources have been provided by the Consortium des Équipements de Calcul Intensif (CÉCI), funded by the Fonds de la Recherche Scientifiques de Belgique (F.R.S.-FNRS) under Grant No. 2.5020.11. D.B. is a FNRS Research Director. Y.O. acknowledges funding from the FRS-FNRS under the grant F.4534.21 (MIS-IMAGINE). EZ-C is a Royal Society Leverhulme Trust Senior Research fellow (SRF\R1\201089). Y.O. is grateful for the fruitful discussions with Prof. Juan-Carlos Sancho-Garcia from the University of Alicante and Prof. Luca Muccioli from the University of Bologna.
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Dive into the research topics of 'Enhancing Thermally Activated Delayed Fluorescence by Fine-Tuning the Dendron Donor Strength'. Together they form a unique fingerprint.Projects
- 1 Finished
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Equipment renewal for the Consortium des Equipements de Calcul Intensif (CECI)
Bontempi, G. (PI), CHAMPAGNE, B. (CoPI), Geuzaine , C. (CoPI), RIGNANESE, G. M. (CoPI) & Lazzaroni, R. (CoPI)
1/01/22 → 31/12/23
Project: Research
Equipment
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High Performance Computing Technology Platform
Champagne, B. (Manager)
Technological Platform High Performance ComputingFacility/equipment: Technological Platform