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Abstract
With the surge of interest in multiresonant thermally activated delayed fluorescent (MR-TADF) materials, it is important that there exist computational methods to accurately model their excited states. Here, building on our previous work, we demonstrate how the spin-component scaling second-order approximate coupled-cluster (SCS-CC2), a wavefunction-based method, is robust at predicting the EST(i.e., the energy difference between the lowest singlet S1and triplet T1excited states) of a large number of MR-TADF materials, with a mean average deviation (MAD) of 0.04 eV compared to experimental data. Time-dependent density functional theory calculations with the most common DFT functionals as well as the consideration of the Tamm-Dancoff approximation (TDA) consistently predict a much larger ESTas a result of a poorer account of Coulomb correlation as compared to SCS-CC2. Very interestingly, the use of a metric to assess the importance of higher order excitations in the SCS-CC2 wavefunctions shows that Coulomb correlation effects are substantially larger in the lowest singlet compared to the corresponding triplet and need to be accounted for a balanced description of the relevant electronic excited states. This is further highlighted with coupled cluster singles-only calculations, which predict very different S1energies as compared to SCS-CC2 while T1energies remain similar, leading to very large EST, in complete disagreement with the experiments. We compared our SCS-CC2/cc-pVDZ with other wavefunction approaches, namely, CC2/cc-pVDZ and SOS-CC2/cc-pVDZ leading to similar performances. Using SCS-CC2, we investigate the excited-state properties of MR-TADF emitters showcasing large ET2T1for the majority of emitters, while π-electron extension emerges as the best strategy to minimize EST. We also employed SCS-CC2 to evaluate donor-acceptor systems that contain a MR-TADF moiety acting as the acceptor and show that the broad emission observed for some of these compounds arises from the solvent-promoted stabilization of a higher-lying charge-transfer singlet state (S2). This work highlights the importance of using wavefunction methods in relation to MR-TADF emitter design and associated photophysics.
Original language | English |
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Pages (from-to) | 4903-4918 |
Number of pages | 16 |
Journal | Journal of Chemical Theory and Computation |
Volume | 18 |
Issue number | 8 |
DOIs | |
Publication status | Published - 9 Aug 2022 |
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Dive into the research topics of 'Modeling of Multiresonant Thermally Activated Delayed Fluorescence Emitters─Properly Accounting for Electron Correlation Is Key!'. 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