Symmetry‐Induced Singlet‐Triplet Inversions in Non‐Alternant Hydrocarbons**

Blaskovits, J. Terence; Garner, Marc H.; Corminbœuf, Clémence

doi:10.1002/ange.202218156

Cited by 4 publications

(1 citation statement)

References 68 publications

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“…Introduction -Molecules with an inverted singlettriplet energy gap (INVEST) have become a hot research topic as they would enable highly efficient emitters for organic light-emitting diodes (OLEDs). [1][2][3][4][5][6][7][8][9][10][11][12] In OLEDs, excited states (or excitons) are created by recombining electrons and holes. 13 According to Fermi-Dirac spin statistics, the ratio of singlet to triplet excited states generated via recombination is 1:3.…”

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confidence: 99%

∆DFT predicts inverted singlet-triplet gaps with chemical accuracy at a fraction of the cost of wavefunction-based approaches

Kunze,

Froitzheim,

Hansen

et al. 2024

Preprint

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Efficient OLEDs must quickly convert singlet and triplet excitons into photons. Molecules with an inverted singlet-triplet energy gap (INVEST) are promising candidates for this task. However, typical INVEST molecules have drawbacks like too low oscillator strengths and excitation energies. High-throughput screening could identify suitable INVEST molecules, but existing methods are problematic: The workhorse method TD-DFT cannot reproduce gap inversion, while wavefunction-based methods are too slow. This study proposes a state-specific method based on unrestricted Kohn-Sham DFT with common hybrid functionals. Tuned on the new INVEST15 benchmark set, this method achieves an error of less than 1 kcal/mol, which is traced back to error cancellation between spin contamination and dynamic correlation. Applied to the larger and structurally diverse NAH159 set in a black-box fashion, the method maintains a small error (1.2 kcal/mol) and accurately predicts gap signs in 83% of cases, confirming its robustness and suitability for screening workflows.

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mentioning

confidence: 99%

∆DFT predicts inverted singlet-triplet gaps with chemical accuracy at a fraction of the cost of wavefunction-based approaches

Kunze,

Froitzheim,

Hansen

et al. 2024

Preprint

View full text Add to dashboard Cite

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Rational Design of Organic Emitters with Inverted Singlet–Triplet Gaps for Enhanced Exciton Management

Sanyam,

Sorout,

Mondal

2024

J. Phys. Chem. A

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In organic light-emitting diodes (OLEDs), the pursuit of efficient molecular emitters has led to the development of thermally activated delayed fluorescence (TADF) molecules. While TADF compounds have promising properties, they face challenges such as energy gap constraints and uphill exciton transfer. Inverted emitters (INVEST) offer a novel solution with an inverted singlet−triplet energy (ΔE ST ) gap, enabling efficient utilization of excitons. This study examines the design and computational analysis of an array of molecules, including 23 INVEST emitters and remaining with positive energy gaps. Within the STEOM-DLPNO−CCSD framework, we explore the role of various molecular fragments in determining ΔE ST . We also assess the importance of dynamic spin-polarization (DSP) obtained via the Pariser−Parr−Pople (PPP) scheme in energy gap determination. Exciting trends emerged from our results, with pentalenecontaining compounds consistently manifesting negative ΔE ST values while their naphthalene counterparts exhibited contrasting behavior. Moreover, we observed a negative DSP correlates with inverted singlet−triplet gaps. Overall, this research advances OLED materials through molecular design and computational analysis, offering avenues for optimizing exciton management and enhancing device performance.

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Searching the Best Double-Hybrid Density Functional to Correctly Predict the Singlet–Triplet Excited-State Inversion in Organic Systems

Derradji,

Valverde,

Brémond

et al. 2024

J. Phys. Chem. C

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The theoretically disclosed, and experimentally confirmed, energy inversion of the lowest singlet (S 1 ) and triplet (T 1 ) excited states of organic molecules (i.e., Hund's rule violation) is investigated herein with the aid of modern and nonempirically derived double-hybrid (DH) density functionals, in the search of the best trade-off between accuracy and computational cost of viable electronic structure methods. For that purpose, we have selected a family of parameter-free expressions differing in their specific formulation (DFT-0DH, DFT-QIDH, DFT0-2, SOS1-DFT-0DH, SOS1-DFT-QIDH, SOS1-DFT0-2, RSX-DFT-0DH, RSX-DFT-QIDH, SOS1-RSX-DFT-0DH, and SOS1-RSX-DFT-QIDH) as well as in the underlying exchange−correlation functional used (PBE vs r 2 SCAN). For the sake of evaluating which DH can correctly describe the singlet−triplet excited-state energy inversion, second-order approximate with singles and doubles method with a spin-component scaling (SCS-CC2) and equation-of-motion coupled cluster singles and doubles (EOM-CCSD) calculations are also carried out. The results highlight the importance of the delicate balance between all the energy terms composing DH density functionals, with the correlation part being particularly significant for achieving the most accurate results. We have also derived a new DH density functional (PBE-DH-INVEST) exploiting that relationship, providing low error metrics and expected to yield robust results in, e.g., high-throughput studies.

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Symmetry‐Induced Singlet‐Triplet Inversions in Non‐Alternant Hydrocarbons**

Cited by 4 publications

References 68 publications

∆DFT predicts inverted singlet-triplet gaps with chemical accuracy at a fraction of the cost of wavefunction-based approaches

∆DFT predicts inverted singlet-triplet gaps with chemical accuracy at a fraction of the cost of wavefunction-based approaches

Rational Design of Organic Emitters with Inverted Singlet–Triplet Gaps for Enhanced Exciton Management

Searching the Best Double-Hybrid Density Functional to Correctly Predict the Singlet–Triplet Excited-State Inversion in Organic Systems

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