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The role of excited-state character, structural relaxation, and symmetry breaking in enabling delayed fluorescence activity in push-pull chromophores
journal contribution
posted on 2021-11-16, 11:56 authored by Patrick Kimber, Pooja GoddardPooja Goddard, Iain Wright, Felix PlasserFelix PlasserThermally activated delayed fluorescence (TADF) is a current promising route for generating highly
efficient light-emitting devices. However, the design process of new chromophores is hampered by
the complicated underlying photophysics. In this work, four closely related donor-π-acceptor-π-donor
systems are investigated, two of which were synthesised previously, with the aim of elucidating their
varying effectiveness for TADF. We outline that the frontier orbitals are insufficient for discriminating
between the molecules. Subsequently, a detailed analysis of the excited states at a correlated ab
initio level highlights the presence of a number of closely spaced singlet and triplet states of varying
character. Results from five density functionals are compared against this reference revealing dramatic
changes in, both, excited state energies and wavefunctions following variations in the amount of
Hartree-Fock exchange included. Excited-state minima are optimised in solution showing the crucial
role of structural variations and symmetry breaking for producing a strongly emissive S1 state. The
adiabatic singlet-triplet gaps thus obtained depend strongly on the range separation parameter used
in the hybrid density functional calculations. More generally, this work highlights intricate differences
present between singlet and triplet excited state wavefunctions and the challenges in describing them
accurately.
History
School
- Science
Department
- Chemistry
Published in
Physical Chemistry Chemical PhysicsVolume
23Issue
46Pages
26135-26150Publisher
Royal Society of Chemistry (RSC)Version
- VoR (Version of Record)
Rights holder
© The AuthorsPublisher statement
This is an Open Access Article. It is published by Royal Society of Chemistry under the Creative Commons Attribution 4.0 International Licence (CC BY). Full details of this licence are available at: https://creativecommons.org/licenses/by/4.0/Acceptance date
2021-11-05Publication date
2021-11-08Copyright date
2021ISSN
1463-9076eISSN
1463-9084Publisher version
Language
- en
Depositor
Dr Felix Plasser . Deposit date: 15 November 2021Usage metrics
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