Molecular Design Based on Donor-Weak Donor Scaffold for Blue Thermally-Activated Delayed Fluorescence Designed by Combinatorial DFT Calculations

Tsuchiya, Youichi; Tsuji, Keita; Inada, Ko; Bencheikh, Fatima; Geng, Yanfang; Kwak, Hyunwook; Mustard, Thomas J. L.; Nakanotani, Hajime; Adachi, Chihaya

doi:10.3389/fchem.2020.00403

Cited by 26 publications

(37 citation statements)

References 25 publications

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“…For DTCz-DPz, TDA-DFT predicted a higher energy HLCT transition on 340 nm and a LE transition on the carbazole moiety at 300 nm (Table S3). The oscillator strengths (f) for DTCz-Pz and DTCz-DPz are calculated to be 0.2514 and 0.5255, respectively, from the spectra, [24] which are consistent with the trend observed from the TDADFT calculations (0.2414 and 1.3927, respectively). The steady-state PL spectra for DTCz-Pz and DTC-DPz are shown in Figure 4b and Figure 4c, respectively.…”

Section: Photophysical Propertiessupporting

confidence: 83%

Planar and Rigid Pyrazine‐Based TADF Emitter for Deep Blue Bright Organic Light‐Emitting Diodes

et al. 2021

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Two blue thermally activated delayed fluorescence (TADF) emitters bearing di-tert-butyl carbazoles as the electron donor groups and pyrazine (DTCz-Pz) or dipyrazine (DTCz-Pz) as the electron acceptor are presented. The DFT calculations predict DTCz-Pz and DTCz-DPz to possess high S 1 energies (3.19 eV and 3.08 eV, respectively), and relatively large ΔE ST values (0.52 eV and 0.56 eV, respectively). The closely layered intermediate triplet states between S 1 and T 1 , predicted by DFT calculations, are expected to facilitate the reverse intersystem crossing (RISC) and improve spin-vibronic coupling efficiency between the excited states, even the relatively larger ΔE ST s. The ΔE ST s for DTCz-Pz and DTCz-DPz are 0.27 eV and 0.38 eV, and both molecules show high photoluminescence quantum yields (65 %, and 70 %, respectively). The decay lifetimes show temperature dependence in a PPT host, which is consistent with the fact that both molecules are TADF emitters in PPT. The OLEDs based on DTCz-Pz exhibit deep blue emission with λ EL of 460 nm and CIE of (0.15, 0.16). The maximum external quantum efficiency (EQE max ) reaches 11.6 %, with a maximum luminance (L max ) of up to 6892 cd m À 2 , while the device based on DTCz-DPz exhibits sky blue emission with λ EL of 484 nm and CIE of (0.15, 0.30), an EQE max of 7.2 %, and L max of 8802 cd m À 2 .

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Section: Photophysical Propertiessupporting

confidence: 83%

Planar and Rigid Pyrazine‐Based TADF Emitter for Deep Blue Bright Organic Light‐Emitting Diodes

et al. 2021

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“…For DTCz-DPz, TDA-DFT predicted a higher energy HLCT transition on 340 nm and a LE transition on the carbazole moiety at 300 nm (Table S2). The oscillator strengths (f) for DTCz-Pz and DTCz-DPz are calculated to be 0.2514 and 0.5255, respectively, from the spectra, [24] which are consistent with the trend observed from the TDADFT calculations (0.2414 and The time-resolved PL decays of these materials were measured in 10 -5 M toluene solution under nitrogen (Figure 5). In both compounds, the emission decays with bi-exponential kinetics.…”

Section: Photophysical Propertiessupporting

confidence: 82%

Planar and Rigid Pyrazine Based TADF Emitter for Deep Blue Bright Organic Light Emitting Diodes

Rajamalli¹,

Chen²,

Suresh³

et al. 2021

Preprint

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Two blue thermally activated delayed fluorescence (TADF) emitters bearing di-tert-butyl carbazoles as the electron donor groups and pyrazine (DTCz-Pz) or dipyrazine (DTCz-Pz) as the electron acceptor are presented. The DFT calculations predict DTCz-Pz and DTCz-DPz to possess high S1 energies (3.19 eV and 3.08 eV, respectively), and relatively large EST values (0.52 eV and 0.56 eV, respectively). The closely layered intermediate triplet states between S1 and T1, predicted by DFT calculations, are expected to facilitate the reverse intersystem crossing (RISC) and improve spin-vibronic coupling efficiency between the excited states even the relatively larger ΔESTs. The ΔESTs for DTCz-Pz and DTCz-DPz are 0.27 eV and 0.38 eV, and both molecules show high photoluminescence quantum yields (65%, and 70%, respectively) and the decay lifetimes show temperature dependence in a PPT host, which is consistent that both molecules are TADF emitters in PPT. The OLEDs based on DTCz-Pz exhibit deep blue emission with λEL of 460 nm and CIE of (0.15, 0.16). The maximum external quantum efficiency (EQEmax) reaches 11.6%, with a maximum luminance (Lmax) of up to 6892 cd m-2, while the device based on DTCz-DPz exhibits sky blue emission with λEL of 484 nm and CIE of (0.15, 0.30), an EQEmax of 7.2%, and Lmax of 8802 cd m-2.

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“…The rather slow nature of the TADF process can be related to the fact that, even though there is participation of a higher CT triplet state in the RISC process and

E_{a}^{RISC}

is small enough for efficient TADF, S 1 , T 1 , and T 2 have all a similar CT character, leading to slow upconversion. [ 27,29,30 ]…”

Section: Resultsmentioning

confidence: 99%

Thermally Activated Delayed Fluorescence Properties of Trioxoazatriangulene Derivatives Modified with Electron Donating Groups

Tsuchiya

Ishikawa

Lee

et al. 2021

Advanced Optical Materials

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With the aim of achieving high‐performance thermally activated delayed fluorescence, a series of trioxoazatriangulene derivatives are systematically developed by modifying the donor substituents. The emission colors are shifted from green to greenish‐yellow and to yellow with rather broad spectral widths of 70–95 nm by introducing carbazole, triphenylamine, or diphenylamine donor units, indicating that each emission originates from a charge‐transfer transition. On the other hand, the trioxoazatriangulene modified with three diphenylamines shows orange emission with a narrow emission spectrum (45 nm), suggesting that the transition mainly originates from a multiple resonance effect.

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Molecular Design Based on Donor-Weak Donor Scaffold for Blue Thermally-Activated Delayed Fluorescence Designed by Combinatorial DFT Calculations

Cited by 26 publications

References 25 publications

Planar and Rigid Pyrazine‐Based TADF Emitter for Deep Blue Bright Organic Light‐Emitting Diodes

Planar and Rigid Pyrazine‐Based TADF Emitter for Deep Blue Bright Organic Light‐Emitting Diodes

Planar and Rigid Pyrazine Based TADF Emitter for Deep Blue Bright Organic Light Emitting Diodes

Thermally Activated Delayed Fluorescence Properties of Trioxoazatriangulene Derivatives Modified with Electron Donating Groups

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