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Froitzheim T, Kunze L, Grimme S, Herbert JM, Mewes JM. Benchmarking Charge-Transfer Excited States in TADF Emitters: ΔDFT Outperforms TD-DFT for Emission Energies. J Phys Chem A 2024; 128:6324-6335. [PMID: 39028862 DOI: 10.1021/acs.jpca.4c03273] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/21/2024]
Abstract
Charge-transfer (CT) excited states are crucial to organic light-emitting diodes (OLEDs), particularly to those based on thermally activated delayed fluorescence (TADF). However, accurately modeling CT states remains challenging, even with modern implementations of (time-dependent) density functional theory [(TD-)DFT], especially in a dielectric environment. To identify shortcomings and improve the methodology, we previously established the STGABS27 benchmark set with highly accurate experimental references for the adiabatic energy gap between the lowest singlet and triplet excited states (ΔEST). Here, we diversify this set to the STGABS27-EMS benchmark by including experimental emission energies (Eem) and use this new set to (re)-evaluate various DFT-based approaches. Surprisingly, these tests demonstrate that a state-specific (un)restricted open-shell Kohn-Sham (U/ROKS) DFT coupled with a polarizable continuum model for perturbative state-specific nonequilibrium solvation (ptSS-PCM) provides exceptional accuracy for predicting Eem over a wide range of density functionals. In contrast, the main workhorse of the field, Tamm-Dancoff-approximated TD-DFT (TDA-DFT) paired with the same ptSS-PCM, is distinctly less accurate and strongly functional-dependent. More importantly, while TDA-DFT requires the choice of two very different density functionals for good performance on either ΔEST or Eem, the time-independent U/ROKS/PCM approaches deliver excellent accuracy for both quantities with a wide variety of functionals.
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Affiliation(s)
- Thomas Froitzheim
- Mulliken Center for Theoretical Chemistry, University of Bonn, Beringstr. 4, 53115 Bonn, Germany
| | - Lukas Kunze
- Mulliken Center for Theoretical Chemistry, University of Bonn, Beringstr. 4, 53115 Bonn, Germany
| | - Stefan Grimme
- Mulliken Center for Theoretical Chemistry, University of Bonn, Beringstr. 4, 53115 Bonn, Germany
| | - John M Herbert
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio 43210, United States
| | - Jan-Michael Mewes
- Mulliken Center for Theoretical Chemistry, University of Bonn, Beringstr. 4, 53115 Bonn, Germany
- beeOLED GmbH, Niedersedlitzer Str. 75 C, 01257 Dresden, Germany
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2
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Froitzheim T, Grimme S, Mewes JM. Either Accurate Singlet-Triplet Gaps or Excited-State Structures: Testing and Understanding the Performance of TD-DFT for TADF Emitters. J Chem Theory Comput 2022; 18:7702-7713. [PMID: 36409831 DOI: 10.1021/acs.jctc.2c00905] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The energy gap between the lowest singlet and triplet excited states (ΔEST) is a key property of thermally activated delayed fluorescence (TADF) emitters, where these states are dominated by charge-transfer (CT) character. Despite its well-known shortcomings concerning CT states, time-dependent density functional theory (TD-DFT) is widely used to predict this gap and study TADF. Moreover, polar CT states exhibit a strong interaction with their molecular environment, which further complicates their computational description. Addressing these two major challenges, this work studies the performance of Tamm-Dancoff-approximated TD-DFT (TDA-DFT) on the recent STGABS27 benchmark set,1 exploring different strategies to include orbital and structural relaxation, as well as dielectric embedding. The results show that the best-performing strategy is to calculate ΔEST at the ground-state structure using functionals with a surprisingly small amount of Fock exchange of ≈10% and without a (complete) solvent model. However, as this approach heavily relies on error cancellation to mimic dielectric relaxation, it is not robust and exhibits large systematic deviations in excited state energies, state characters, and structures. More rigorous approaches, including state-specific solvation, do not share these systematic deviations, but their predicted ΔEST values exhibit larger statistical errors. We thus conclude that for the description of CT states in dielectric environments, none of the tested TDA-DFT methods is competitive with the recently presented ROKS/PCM approach regarding robustness, accuracy, and computational efficiency.
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Affiliation(s)
- Thomas Froitzheim
- Mulliken Center for Theoretical Chemistry, University of Bonn, Beringstr. 4, 53115Bonn, Germany
| | - Stefan Grimme
- Mulliken Center for Theoretical Chemistry, University of Bonn, Beringstr. 4, 53115Bonn, Germany
| | - Jan-Michael Mewes
- Mulliken Center for Theoretical Chemistry, University of Bonn, Beringstr. 4, 53115Bonn, Germany
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3
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Eşme A. Structural, spectral characterization, and topological study of (E)-5-(diethylamino)-2-((3,5-dinitrophenylimino)methyl)phenol. Struct Chem 2022. [DOI: 10.1007/s11224-022-01956-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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4
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Grabarz AM, Ośmiałowski B. Benchmarking Density Functional Approximations for Excited-State Properties of Fluorescent Dyes. Molecules 2021; 26:7434. [PMID: 34946515 PMCID: PMC8703901 DOI: 10.3390/molecules26247434] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2021] [Revised: 11/28/2021] [Accepted: 12/04/2021] [Indexed: 12/05/2022] Open
Abstract
This study presents an extensive analysis of the predictive power of time-dependent density functional theory in determining the excited-state properties of two groups of important fluorescent dyes, difluoroboranes and hydroxyphenylimidazo[1,2-a]pyridine derivatives. To ensure statistically meaningful results, the data set is comprised of 85 molecules manifesting diverse photophysical properties. The vertical excitation energies and dipole moments (in the electronic ground and excited states) of the aforementioned dyes were determined using the RI-CC2 method (reference) and with 18 density functional approximations (DFA). The set encompasses DFAs with varying amounts of exact exchange energy (EEX): from 0% (e.g., SVWN, BLYP), through a medium (e.g., TPSSh, B3LYP), up to a major contribution of EEX (e.g., BMK, MN15). It also includes range-separated hybrids (CAM-B3LYP, LC-BLYP). Similar error profiles of vertical energy were obtained for both dye groups, although the errors related to hydroxyphenylimidazopiridines are significantly larger. Overall, functionals including 40-55% of EEX (SOGGA11-X, BMK, M06-2X) ensure satisfactory agreement with the reference vertical excitation energies obtained using the RI-CC2 method; however, MN15 significantly outperforms them, providing a mean absolute error of merely 0.04 eV together with a very high correlation coefficient (R2 = 0.98). Within the investigated set of functionals, there is no single functional that would equally accurately determine ground- and excited-state dipole moments of difluoroboranes and hydroxyphenylimidazopiridine derivatives. Depending on the chosen set of dyes, the most accurate μGS predictions were delivered by MN15 incorporating a major EEX contribution (difluoroboranes) and by PBE0 containing a minor EEX fraction (hydroxyphenylimidazopiridines). Reverse trends are observed for μES, i.e., for difluoroboranes the best results were obtained with functionals including a minor fraction of EEX, specifically PBE0, while in the case of hydroxyphenylimidazopiridines, much more accurate predictions were provided by functionals incorporating a major EEX contribution (BMK, MN15).
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Affiliation(s)
- Anna M. Grabarz
- Faculty of Chemistry, Wrocław University of Science and Technology, Wyb. Wyspiańskiego 27, PL-50370 Wrocław, Poland
| | - Borys Ośmiałowski
- Faculty of Chemistry, Nicolaus Copernicus University, Gagarina 7, PL-87100 Toruń, Poland;
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5
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Ait Tayeb MA, Tchouar N, Miannay FA, Idrissi A. Effect of the mixture composition of C4mimBF4/acetonitrile on the charge transfer in Coumarin 153: DFT and TD-DFT analysis. J Mol Liq 2021. [DOI: 10.1016/j.molliq.2021.116830] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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6
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Guido CA, Chrayteh A, Scalmani G, Mennucci B, Jacquemin D. Simple Protocol for Capturing Both Linear-Response and State-Specific Effects in Excited-State Calculations with Continuum Solvation Models. J Chem Theory Comput 2021; 17:5155-5164. [PMID: 34224244 DOI: 10.1021/acs.jctc.1c00490] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We present an effective computational protocol (cLR2) to describe both solvatochromism and fluorosolvatochromism. This protocol, which couples the polarizable continuum model to time-dependent density functional theory, simultaneously accounts for both linear-response and state-specific solvation effects. A series of test cases, including solvatochromic and fluorosolvatochromic compounds and excited-state intramolecular proton transfers, are used to highlight that cLR2 is especially beneficial for modeling bright excitations possessing a significant charge-transfer character, as well as cases in which an accurate balance between states of various polarities should be restored.
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Affiliation(s)
- Ciro A Guido
- Université de Nantes, CNRS, CEISAM UMR 6230, F-44000 Nantes, France.,Dipartimento di Scienze Chimiche, Università di Padova, Via F. Marzolo 1, I-35131 Padova, Italy
| | - Amara Chrayteh
- Université de Nantes, CNRS, CEISAM UMR 6230, F-44000 Nantes, France
| | - Giovanni Scalmani
- Gaussian Inc., 340 Quinnipiac St Bldg 40, Wallingford, Connecticut 06492, United States
| | - Benedetta Mennucci
- Dipartimento di Chimica e Chimica Industriale, University of Pisa, Via Moruzzi 3, 56124 Pisa, Italy
| | - Denis Jacquemin
- Université de Nantes, CNRS, CEISAM UMR 6230, F-44000 Nantes, France
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7
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Herbert JM. Dielectric continuum methods for quantum chemistry. WILEY INTERDISCIPLINARY REVIEWS-COMPUTATIONAL MOLECULAR SCIENCE 2021. [DOI: 10.1002/wcms.1519] [Citation(s) in RCA: 37] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- John M. Herbert
- Department of Chemistry and Biochemistry The Ohio State University Columbus Ohio USA
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8
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Electronic and nonlinear optical properties of 3-(((2-substituted-4-nitrophenyl)imino)methyl)phenol. COMPUT THEOR CHEM 2020. [DOI: 10.1016/j.comptc.2020.113050] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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9
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Nelson TR, White AJ, Bjorgaard JA, Sifain AE, Zhang Y, Nebgen B, Fernandez-Alberti S, Mozyrsky D, Roitberg AE, Tretiak S. Non-adiabatic Excited-State Molecular Dynamics: Theory and Applications for Modeling Photophysics in Extended Molecular Materials. Chem Rev 2020; 120:2215-2287. [PMID: 32040312 DOI: 10.1021/acs.chemrev.9b00447] [Citation(s) in RCA: 213] [Impact Index Per Article: 53.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Optically active molecular materials, such as organic conjugated polymers and biological systems, are characterized by strong coupling between electronic and vibrational degrees of freedom. Typically, simulations must go beyond the Born-Oppenheimer approximation to account for non-adiabatic coupling between excited states. Indeed, non-adiabatic dynamics is commonly associated with exciton dynamics and photophysics involving charge and energy transfer, as well as exciton dissociation and charge recombination. Understanding the photoinduced dynamics in such materials is vital to providing an accurate description of exciton formation, evolution, and decay. This interdisciplinary field has matured significantly over the past decades. Formulation of new theoretical frameworks, development of more efficient and accurate computational algorithms, and evolution of high-performance computer hardware has extended these simulations to very large molecular systems with hundreds of atoms, including numerous studies of organic semiconductors and biomolecules. In this Review, we will describe recent theoretical advances including treatment of electronic decoherence in surface-hopping methods, the role of solvent effects, trivial unavoided crossings, analysis of data based on transition densities, and efficient computational implementations of these numerical methods. We also emphasize newly developed semiclassical approaches, based on the Gaussian approximation, which retain phase and width information to account for significant decoherence and interference effects while maintaining the high efficiency of surface-hopping approaches. The above developments have been employed to successfully describe photophysics in a variety of molecular materials.
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Affiliation(s)
- Tammie R Nelson
- Theoretical Division , Los Alamos National Laboratory , Los Alamos , New Mexico 87545 , United States
| | - Alexander J White
- Theoretical Division , Los Alamos National Laboratory , Los Alamos , New Mexico 87545 , United States
| | - Josiah A Bjorgaard
- Theoretical Division , Los Alamos National Laboratory , Los Alamos , New Mexico 87545 , United States
| | - Andrew E Sifain
- Theoretical Division , Los Alamos National Laboratory , Los Alamos , New Mexico 87545 , United States.,U.S. Army Research Laboratory , Aberdeen Proving Ground , Maryland 21005 , United States
| | - Yu Zhang
- Theoretical Division , Los Alamos National Laboratory , Los Alamos , New Mexico 87545 , United States
| | - Benjamin Nebgen
- Theoretical Division , Los Alamos National Laboratory , Los Alamos , New Mexico 87545 , United States
| | | | - Dmitry Mozyrsky
- Theoretical Division , Los Alamos National Laboratory , Los Alamos , New Mexico 87545 , United States
| | - Adrian E Roitberg
- Department of Chemistry , University of Florida , Gainesville , Florida 32611 , United States
| | - Sergei Tretiak
- Theoretical Division , Los Alamos National Laboratory , Los Alamos , New Mexico 87545 , United States
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10
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Zhang X, Shi Y, Cai L, Zhou Y, Wang CK, Lin L. Solvent effect on the photophysical properties of thermally activated delayed fluorescence molecules. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2020; 225:117473. [PMID: 31470345 DOI: 10.1016/j.saa.2019.117473] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2019] [Revised: 07/27/2019] [Accepted: 08/15/2019] [Indexed: 06/10/2023]
Abstract
As the third-generation organic electroluminescent materials, thermally activated delayed fluorescence (TADF) molecules have become the research focus recently. Significant solvent effect on TADF molecules were found experimentally, while theoretical investigations are quite limited. In this work, the solvent effect on photophysical properties of DCBPy and DTCBPy are investigated with first-principles calculations. The solvent polarity has slight influence on the molecular geometries and orbitals, while it can decrease the energy gap between the first singlet excited state (S1) and first triplet excited state (T1) significantly. Both the oscillator strength and the radiation rates of S1 increase with larger solvent polarity. The large energy gap between S1 and T1 induce negligible intersystem crossing (ISC) and reverse ISC rates between them, which also indicates higher triplet excited states are involved in the up-conversion process. Our results provide valuable information about solvent influence on the light-emitting properties of TADF molecules, which could help one better understand the light-emitting mechanism of them and favor the design of TADF molecules.
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Affiliation(s)
- Xiaotong Zhang
- Shandong Province Key Laboratory of Medical Physics and Image Processing Technology, School of Physics and Electronics, Shandong Normal University, 250014 Jinan, China
| | - Yurong Shi
- Shandong Province Key Laboratory of Medical Physics and Image Processing Technology, School of Physics and Electronics, Shandong Normal University, 250014 Jinan, China
| | - Lei Cai
- Shandong Province Key Laboratory of Medical Physics and Image Processing Technology, School of Physics and Electronics, Shandong Normal University, 250014 Jinan, China
| | - Yong Zhou
- Shandong Province Key Laboratory of Medical Physics and Image Processing Technology, School of Physics and Electronics, Shandong Normal University, 250014 Jinan, China
| | - Chuan-Kui Wang
- Shandong Province Key Laboratory of Medical Physics and Image Processing Technology, School of Physics and Electronics, Shandong Normal University, 250014 Jinan, China.
| | - Lili Lin
- Shandong Province Key Laboratory of Medical Physics and Image Processing Technology, School of Physics and Electronics, Shandong Normal University, 250014 Jinan, China.
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11
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Giovannini T, Riso RR, Ambrosetti M, Puglisi A, Cappelli C. Electronic transitions for a fully polarizable QM/MM approach based on fluctuating charges and fluctuating dipoles: Linear and corrected linear response regimes. J Chem Phys 2019; 151:174104. [PMID: 31703497 DOI: 10.1063/1.5121396] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The fully polarizable Quantum Mechanics/Molecular Mechanics (QM/MM) approach based on fluctuating charges and fluctuating dipoles, named QM/FQFμ [T. Giovannini et al., J. Chem. Theory Comput. 15, 2233 (2019)], is extended to the calculation of vertical excitation energies of solvated molecular systems. Excitation energies are defined within two different solvation regimes, i.e., linear response (LR), where the response of the MM portion is adjusted to the QM transition density, and corrected-Linear Response (cLR) in which the MM response is adjusted to the relaxed QM density, thus being able to account for charge equilibration in the excited state. The model, which is specified in terms of three physical parameters (electronegativity, chemical hardness, and polarizability) is applied to vacuo-to-water solvatochromic shifts of aqueous solutions of para-nitroaniline, pyridine, and pyrimidine. The results show a good agreement with their experimental counterparts, thus highlighting the potentialities of this approach.
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Affiliation(s)
- Tommaso Giovannini
- Department of Chemistry, Norwegian University of Science and Technology, 7491 Trondheim, Norway
| | | | | | | | - Chiara Cappelli
- Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa, Italy
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12
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Caricato M. CCSD‐PCM Excited State Energy Gradients with the Linear Response Singles Approximation to Study the Photochemistry of Molecules in Solution. CHEMPHOTOCHEM 2019. [DOI: 10.1002/cptc.201900152] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Marco Caricato
- Department of ChemistryUniversity of Kansas 1567 Irving Hill Rd. Lawrence KS 66045 USA
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13
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Study on the spectral complementary composite dye molecules designed for high performance dye-sensitized solar cells: A theoretical investigation. COMPUT THEOR CHEM 2019. [DOI: 10.1016/j.comptc.2019.03.017] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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14
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Kulinich AV, Ishchenko AA. Electronic structure of merocyanine dyes derived from 3H-indole and malononitrile in the ground and excited states: DFT/TD-DFT analysis. COMPUT THEOR CHEM 2019. [DOI: 10.1016/j.comptc.2019.03.018] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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15
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García-Iriepa C, Zemmouche M, Ponce-Vargas M, Navizet I. The role of solvation models on the computed absorption and emission spectra: the case of fireflies oxyluciferin. Phys Chem Chem Phys 2019; 21:4613-4623. [DOI: 10.1039/c8cp07352j] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Absorption and emission energies calculation covering both implicit and explicit solvation models using oxyluciferin as the case of study.
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Affiliation(s)
- Cristina García-Iriepa
- Université Paris-Est
- Laboratoire Modélisation et Simulation Multi Échelle
- MSME UMR 8208 CNRS
- UPEM
- 77454 Marne-la-Vallée
| | - Madjid Zemmouche
- Université Paris-Est
- Laboratoire Modélisation et Simulation Multi Échelle
- MSME UMR 8208 CNRS
- UPEM
- 77454 Marne-la-Vallée
| | - Miguel Ponce-Vargas
- Université Paris-Est
- Laboratoire Modélisation et Simulation Multi Échelle
- MSME UMR 8208 CNRS
- UPEM
- 77454 Marne-la-Vallée
| | - Isabelle Navizet
- Université Paris-Est
- Laboratoire Modélisation et Simulation Multi Échelle
- MSME UMR 8208 CNRS
- UPEM
- 77454 Marne-la-Vallée
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16
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Vérité PM, Guido CA, Jacquemin D. First-principles investigation of the double ESIPT process in a thiophene-based dye. Phys Chem Chem Phys 2019; 21:2307-2317. [DOI: 10.1039/c8cp06969g] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Explanation of the experimental triple emission with theoretical tools requires advanced solvent models.
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Affiliation(s)
- Pauline M. Vérité
- Laboratoire CEISAM – UMR CNRS 6230
- Université de Nantes
- 44322 Nantes Cedex 3
- France
| | - Ciro A. Guido
- Laboratoire CEISAM – UMR CNRS 6230
- Université de Nantes
- 44322 Nantes Cedex 3
- France
| | - Denis Jacquemin
- Laboratoire CEISAM – UMR CNRS 6230
- Université de Nantes
- 44322 Nantes Cedex 3
- France
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17
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Siddique F, Silva CP, Medeiros Silva GT, Lischka H, Quina FH, Aquino AJA. The electronic transitions of analogs of red wine pyranoanthocyanin pigments. Photochem Photobiol Sci 2019; 18:45-53. [DOI: 10.1039/c8pp00391b] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
High level theoretical methods have been used in order to understand structural effects on the absorption spectra of pyranoanthocyanins.
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Affiliation(s)
- Farhan Siddique
- School of Pharmaceutical Science and Technology
- Tianjin University
- Tianjin 300072
- People's Republic of China
| | - Cassio P. Silva
- Instituto de Química
- Universidade de São Paulo
- São Paulo
- Brazil
| | | | - Hans Lischka
- School of Pharmaceutical Science and Technology
- Tianjin University
- Tianjin 300072
- People's Republic of China
- Department of Chemistry and Biochemistry
| | - Frank H. Quina
- Instituto de Química
- Universidade de São Paulo
- São Paulo
- Brazil
| | - Adelia J. A. Aquino
- School of Pharmaceutical Science and Technology
- Tianjin University
- Tianjin 300072
- People's Republic of China
- Department of Chemistry and Biochemistry
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18
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Duchemin I, Guido CA, Jacquemin D, Blase X. The Bethe-Salpeter formalism with polarisable continuum embedding: reconciling linear-response and state-specific features. Chem Sci 2018; 9:4430-4443. [PMID: 29896384 PMCID: PMC5956976 DOI: 10.1039/c8sc00529j] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2018] [Accepted: 04/02/2018] [Indexed: 11/25/2022] Open
Abstract
The Bethe-Salpeter equation (BSE) formalism has been recently shown to be a valuable alternative to time-dependent density functional theory (TD-DFT) with the same computing time scaling with system size. In particular, problematic transitions for TD-DFT such as charge-transfer, Rydberg and cyanine-like excitations were shown to be accurately described with BSE. We demonstrate here that combining the BSE formalism with the polarisable continuum model (PCM) allows us to include simultaneously linear-response and state-specific contributions to solvatochromism. This is confirmed by exploring transitions of various natures (local, charge-transfer, etc.) in a series of solvated molecules (acrolein, indigo, p-nitro-aniline, donor-acceptor complexes, etc.) for which we compare BSE solvatochromic shifts to those obtained by linear-response and state-specific TD-DFT implementations. Such a remarkable and unique feature is particularly valuable for the study of solvent effects on excitations presenting a hybrid localised/charge-transfer character.
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Affiliation(s)
- Ivan Duchemin
- Univ. Grenobles Alpes , CEA, INAC-MEM, L_Sim , F-38000 Grenoble , France . ;
| | - Ciro A Guido
- Laboratoire CEISAM - UMR CNR 6230 , Université de Nantes , 2 Rue de la Houssinière, BP 92208 , 44322 Nantes Cedex 3 , France
- Laboratoire MOLTECH - UMR CNRS 6200 , Université de Angers , 2 Bd Lavoisier , 49045 Angers Cedex , France
| | - Denis Jacquemin
- Laboratoire CEISAM - UMR CNR 6230 , Université de Nantes , 2 Rue de la Houssinière, BP 92208 , 44322 Nantes Cedex 3 , France
| | - Xavier Blase
- Univ. Grenobles Alpes , CNRS , Institut Néel , F-38042 Grenoble , France
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19
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Mewes JM. Modeling TADF in organic emitters requires a careful consideration of the environment and going beyond the Franck-Condon approximation. Phys Chem Chem Phys 2018; 20:12454-12469. [PMID: 29700532 DOI: 10.1039/c8cp01792a] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The origin of the thermally-activated delayed fluorescence (TADF) of three organic emitters is investigated, focusing on the nature of the lowest excited states, their transition properties, as well as the role of the environment. For this purpose, the algebraic-diagrammatic construction for the polarization propagator at second order of perturbation theory [ADC(2)], time-dependent density-functional theory in the Tamm-Dancoff approximation (TDA) and unrestricted Kohn-Sham DFT in combination with the maximum-overlap method (ΔDFT) are employed. The influence of the dielectric environment is rigorously included using different variants of the polarizable continuum model. The calculations reveal the lowest excited singlet and triplet states of all studied emitters to be dominated by charge-transfer (CT) character already in the most apolar environment corresponding to cyclo-hexane. The dielectric stabilization entails a drastic reduction of the singlet-triplet gaps, increasing the calculated TADF rates by several orders of magnitude. Another ingredient for accurate TADF rates is hidden in the excited-state potential-energy surfaces along the donor-acceptor twisting angle. A presence of large, shallow plateaus in apolar environments causes the transition properties to be governed by thermal fluctuations rather than the minimum-energy geometries. This leads to a large increase of the oscillator strengths, as well as a breakdown of the Franck-Condon approximation. The last ingredient is a small but significant spin-orbit coupling (SOC) between the singlet and triplet CT states, which is traced back to a delocalization of the excitation hole or excited electron of the triplet CT state. Taking into account all of these effects, a reasonable agreement with experimental TADF and fluorescence lifetimes is obtained. For this, it proves to be sufficient to consider only the lowest lying singlet and triplet excited states.
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Affiliation(s)
- Jan-Michael Mewes
- Jan-Michael Mewes, Centre For Theoretical Chemistry and Physics, New-Zealand Institute for Advanced Study, Massey University (Albany), Private Bag 102-904, North Shore Mail Centre, 0632 Auckland, New Zealand.
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