Development of multi-resonant thermally activated delayed fluorescence emitters and investigation of the impact of hydrogen bonding on the room temperature phosphorescence
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Date
13/06/2024Author
Supervisor
Grant ID
201906250199
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Thermally activated delayed fluorescence (TADF) materials stand out as a highly promising class of emitters for organic light-emitting diodes (OLEDs), capable of achieving up to 100% internal quantum efficiency. Most of these are organic and so are more sustainable to produce than the commercially employed phosphorescent organometallic complexes. Multiresonant TADF (MR-TADF) emitters have garnered significant attention, particularly as they are bright and generally show narrowband emission, making them well-suited for high-definition (HD) display applications. This work is centered on developing new designs for MR-TADF emitters
that span the entire emission color spectrum for efficient OLEDs. The thesis also explores the impact of restricting molecular motion using hydrogen bonding to suppress nonradiative decay and thus turn on room temperature phosphorescence.
Chapter 1 presents the overview the mechanisms of photoluminescence and electroluminescence along with an overview of the development of TADF emitters, with a specific focus on the MR-TADF emitters.
Chapter 2 demonstrates how the character of the charge transfer excited state can be modulated from short-range charge transfer to long-rang charge transfer through attaching different numbers of donors with different electron-donating strengths onto a MR-TADF emitter core, DiKTa.
Chapter 3 documents how decorating the DiKTa core with three donors can lead to efficient green (3TPA-DiKTa) and red (3DPA-DiKTa) MR-TADF emitters. The devices with much supressed efficiency roll-off were obtained with aid of the HF-OLEDs stack.
In Chapter 4, we introduce a fluorene-bridged double carbonyl/amine-based MR-TADF emitter DDiKTa-F, formed by locking the conformation of the previously reported compound DDiKTa. Using this strategy, DDiKTa-F exhibits a narrower, brighter, and red-shifted emission.
Chapter 5 discusses the development of an orange MR-TADF emitter, DDiKTa-A, based on a design that bridges two DiKTa units via a central aniline.
Chapter 6 reveals the design of a blue MR-TADF emitter (DOBDiKTa) formed by the fusion of two MR-TADF emitters, DiKTa and tBuDOBNA, together. Using this strategy, this compound emits desirably at an intermediate blue emission between the sky blue of DiKTa and the purple of tBuDOBNA.
In Chapter 7, two MR-TADF emitters, 2GtBuCzCO2HDCzB and tBuCzCO2HDCzB, are presented. These emitters exhibited resistance to aggregation and aggregation-caused quenching, even in neat films, by encapsulating the MR-TADF emissive core DtBuCzB within flanking donor-acceptor TADF groups.
Chapter 8 demonstrated the generality of embedding a hydrogen-bonding guest fluorophore into a hydrogen bonded network as a means of activating the RTP through the restriction of the molecular motion.
Chapter 9 presented the experimental methods used in this thesis.
Type
Thesis, PhD Doctor of Philosophy
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Embargo Date: 2025-03-28
Embargo Reason: Thesis restricted in accordance with University regulations. Restricted until 28 March 2025
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Data underpinning Sen Wu's thesis Wu, S., University of St Andrews, 28 Mar 2025. DOI: https://doi.org/10.17630/1b001f08-8896-417e-941f-4ce78de78a5dWu, S., Zhang, L., Wang, J., Gupta, A. K., Samuel, I. D. W., & Zysman-Colman, E. (2023). Merging boron and carbonyl based MR-TADF emitter designs to achieve high performance pure blue OLEDs. Angewandte Chemie International Edition, 62(28), Article e202305182. https://doi.org/10.1002/anie.202305182
Wu, S., Sun, D., & Zysman-Colman, E. (2023). Solution-processed high-performance organic light-emitting diodes containing a green-emitting MR-TADF dendrimer. Journal of the Society for Information Display, 31(6), 450-456. https://doi.org/10.1002/jsid.1204
Wang, T., Gupta, A. K., Wu, S., Slawin, A. M. Z., & Zysman-Colman, E. (2023). Conjugation-modulated excitonic coupling brightens multiple triplet excited states. Journal of the American Chemical Society, 145(3), 1945-1954. https://doi.org/10.1021/jacs.2c12320
Wu, S., Gupta, A. K., Yoshida, K., Gong, J., Hall, D., Cordes, D. B., Slawin, A. M. Z., Samuel, I. D. W., & Zysman-Colman, E. (2022). Highly efficient green and red narrowband emissive organic light-emitting diodes employing multi-resonant thermally activated delayed fluorescence emitters. Angewandte Chemie International Edition, 61(52), Article e202213697. https://doi.org/10.1002/anie.202213697
Wu, S., Li, W., Yoshida, K., Hall, D., Madayanad Suresh, S., Sayner, T., Gong, J., Beljonne, D., Olivier, Y., Samuel, I. D. W., & Zysman-Colman, E. (2022). Excited-state modulation in donor-substituted multiresonant thermally activated delayed fluorescence emitters. ACS Applied Materials & Interfaces, Articles ASAP. Advance online publication. https://doi.org/10.1021/acsami.2c02756
Wang, T., De, J., Wu, S., Gupta, A. K., & Zysman-Colman, E. (2022). Thermally activated and aggregation-regulated excitonic coupling enable emissive high-lying triplet excitons. Angewandte Chemie International Edition, 61(33), Article e202206681. https://doi.org/10.1002/anie.202206681
Poulard, L., Kasemthaveechok, S., Coehlo, M., Kumar, R. A., Frédéric, L., Sumsalee, P., d’Anfray, T., Wu, S., Wang, J., Matulaitis, T., Crassous, J., Zysman-Colman, E., Favereau, L., & Pieters, G. (2022). Circularly polarized-thermally activated delayed fluorescent materials based on chiral bicarbazole donors. Chemical Communications, Advance Article. Advance online publication. https://doi.org/10.1039/D2CC00998F
Wu, S., Hu, Y.-N., Wang, J., Sun, D., Wang, K., Zhang, X.-H., & Zysman-Colman, E. (2024). Efficient orange organic light-emitting diodes employing a central aniline bridged multiresonant thermally activated delayed fluorescence emitter. Journal of Materials Chemistry C, 12(17), 6177-6184. https://doi.org/10.1039/D4TC00506F
Related resources
https://doi.org/10.17630/1b001f08-8896-417e-941f-4ce78de78a5dhttps://doi.org/10.1002/anie.202305182
https://doi.org/10.1002/jsid.1204
https://doi.org/10.1021/jacs.2c12320
https://doi.org/10.1002/anie.202213697
https://doi.org/10.1021/acsami.2c02756
https://doi.org/10.1002/anie.202206681
https://doi.org/10.1039/D2CC00998F
https://doi.org/10.1039/D4TC00506F
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