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Updated: Sep 13, 2025
08:04
Excitonic Hamiltonians for Calculating Optical Absorption Spectra and Optoelectronic Properties of Molecular Aggregates and Solids
Published on: May 27, 2020
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Excited State Dynamics of a MR-TADF Emitter in Host Matrices
Pratiksha Dad1, Alexandra N Stuart1, William J Kendrick2
1School of Chemistry, The University of Sydney, Camperdown, New South Wales 2050, Australia.
The Journal of Physical Chemistry Letters
|July 31, 2025
Summary
Multi-resonance thermally activated delayed fluorescence (MR-TADF) emitters show potential for pure color organic light-emitting diodes (OLEDs). This study reveals a second triplet state in OQAO(mes)3 emitters, influencing delayed fluorescence via reverse intersystem crossing.
Area of Science:
- Materials Science
- Organic Electronics
- Photophysics
Background:
- Multi-resonance thermally activated delayed fluorescence (MR-TADF) emitters offer narrow emission bandwidths for pure color organic light-emitting diodes (OLEDs).
- Understanding their excited-state photophysics is key to enhancing device performance.
Purpose of the Study:
- To investigate the excited-state photophysical properties of the MR-TADF emitter OQAO(mes)3.
- To examine the influence of host matrix polarity on these properties and the resultant delayed fluorescence.
Main Methods:
- Transient absorption spectroscopy.
- Time-resolved fluorescence spectroscopy.
- Host-guest systems with varying polarity, including OLED-relevant hosts.
Main Results:
- A second, lower-lying triplet state was identified in high polarity matrices, consistent with solution studies.
- Interconversion between triplet states allows harvesting of low-lying triplets to bright singlets via reverse intersystem crossing (rISC), generating delayed fluorescence.
- No evidence of exciplex-like interactions impacting the TADF process was observed in host-guest systems.
Conclusions:
- The presence of a second triplet state significantly influences the photophysics of MR-TADF emitters in polar environments.
- Host matrix polarity plays a critical role in determining the photophysical pathways and performance of MR-TADF materials.
- The findings clarify the mechanisms behind delayed fluorescence in OQAO(mes)3, differentiating from exciplex-mediated processes.
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