Triarylboryl-substituted carbazoles as bipolar host materials for efficient green phosphorescent organic light-emitting devices

Lu, Chin‐Wei; Tsai, Chih-Chieh; Huang, Yun-Syuan; Chih, Hsin-Yun; Li, Weicheng; Chiu, Ting-Ya; Chang, Chih-Hao

doi:10.1016/j.dyepig.2018.11.042

Cited by 23 publications

(18 citation statements)

References 39 publications

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“…This phenomenon can be attributed to the S 1 charge‐transfer (CT) character between the donor and acceptor moieties when the target compound is stimulated by light, which results in a considerable change in the dipole moment for the whole molecule from the ground state to the excited state. In addition, when the polarity of the solvent increases, it markedly stabilizes the molecules in the excited state, and therefore causes a redshifted emission . The same behavior can be observed in TH‐2PTZ and TH‐2DPAC .…”

Section: Resultssupporting

confidence: 54%

“…In addition, when the polarity of the solventi ncreases, it markedly stabilizes the molecules in the excited state, and therefore causes a redshifted emission. [22,23] Thes ame behavior can be observed in TH-2PTZ and TH-2DPAC.N otably,aweak emission band occurs in the 400-450 nm region of TH-2PTZ in CH 2 Cl 2 .A t shorter wavelengths, this type of emission differs from the CT band and can often be attributed to localized excitation (LE) presumably owing to the relatively more distorted architecture of TH-2PTZ. [24,25] The delayedf luorescencen ature of TH-2PTZ, TH-2DMAC,a nd TH-2DPAC was supportedb ys howing the nearly microsecond lifetimes (1292-4416 ns) in deoxygenated solution (cf.…”

Section: Photophysical Propertiesmentioning

confidence: 99%

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Facile Generation of Thermally Activated Delayed Fluorescence and Fabrication of Highly Efficient Non‐Doped OLEDs Based on Triazine Derivatives

Chih

Chen

Hsieh

et al. 2019

Chemistry A European J

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As eries of donor-acceptor-donor triazine-based molecules with thermally activated delayedf luorescence (TADF) properties were synthesized to obtain highly efficient blue-emitting OLEDs with non-doped emitting layers (EMLs). The targeted molecules use at riazinec ore as the electron acceptor,a nd ab enzene ring as the conjugated linker with different electrond onors to alternate the energy level of the HOMO to further tune the emission color.T he introduction of long alkyl chains on the triazine core inhibits the unwanted intermolecular D-D/A-A-type p-p interactions, resulting in the intermolecularD -A charget ransfer.T he weak aggregation-causedq uenching (ACQ) effectc aused by the sup-pressed intermolecular D-D/A-A-type p-p interaction further enhancest he emission.T he crowded molecular structure allows the electrond onor and acceptort ob en early orthogonal, thereby reducing the energy gap between triplet and singlet excited states (DE ST ). As ar esult, blue-emitting devices with TH-2DMAC and TH-2DPAC non-doped EMLs showed satisfactory efficiencies of 12.8 %a nd 15.8 %, respectively,w hichi so ne of the highest external quantum efficiency (EQEs) reported for blue TADF emitters( l peak < 475 nm), demonstratingt hat our tailored molecular designsare promising strategies to endow OLEDs with excellent electroluminescent performances.

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Section: Resultssupporting

confidence: 54%

Section: Photophysical Propertiesmentioning

confidence: 99%

Facile Generation of Thermally Activated Delayed Fluorescence and Fabrication of Highly Efficient Non‐Doped OLEDs Based on Triazine Derivatives

Chih

Chen

Hsieh

et al. 2019

Chemistry A European J

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“…Both sets used a thin DPEPO layer as the ECL between the DPEPO EML and the HTL. Furthermore, considering the HOMO energy level matching, di‐[4‐( N , N ‐ditolyl‐amino)‐phenyl]cyclohexane (TAPC) and 4,4’,4”‐tris(carbazol‐9‐yl)‐triphenylamine (TCTA) were combined to form a stepwise HTL in both sets of devices [25c] . Moreover, since 1,3,5‐tri[(3‐pyridyl)‐phen‐3‐yl] benzene (TmPyPB) has a high electron mobility of 1×10 −3 cm 2 V −1 s −1 and a large E T of 2.78 eV, it was used as the electron transport layer (ETL), thereby promoting the carrier balance and the exciton confinement [31] .…”

Section: Resultsmentioning

confidence: 99%

Dicyano‐Imidazole: A Facile Generation of Pure Blue TADF Materials for OLEDs

Liu

Luo

et al. 2021

Chemistry A European J

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A series of dicyano-imidazole-based molecules with thermally activated delayed fluorescence (TADF) properties were synthesized to obtain pure blue-emitting organic lightemitting diodes (OLEDs). The targeted molecules used dicyano-imidazole with a short-conjugated system as the electron acceptor to strong intermolecular π-π interactions, and provide a relatively shallow energy level of the lowest unoccupied molecular orbital (LUMO). The cyano group was selected to improve imidazole as an electron acceptor due to its prominent electron-transporting characteristics. Four different electron donors, that is, 9,9-dimethyl-9,10-dihydroacridine (DMAC), 10H-spiro(acridine-9,9'-fluoren) (SPAC), and 9,9diphenyl-9,10-dihydroacridine (DPAC), were used to alternate the highest occupied molecular orbital (HOMO) energy level to tune the emission color further. The crowded molecular structure in space makes the electron donor and acceptor almost orthogonal, reducing the energy gap (ΔE ST ) between the first excited singlet (S 1 ) and the triplet (T 1 ) states and introducing significant TADF property. The efficiencies of the blue-emissive devices with imM-SPAC and imM-DMAC obtained in this work are the highest among the reported imidazole-based TADF-OLEDs, which are 13.8 % and 13.4 %, respectively. Both of Commission Internationale de l'Eclairage (CIE) coordinates are close to the saturated blue region at (0.17, 0.18) and (0.16, 0.19), respectively. Combining these tailor-made TADF compounds with specific device architectures, electroluminescent (EL) emission from sky-blue to deep-blue could be achieved, proving their great potential in EL applications.

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“…In device A2, to decrease the energy barrier between HTL and EML, a 5 nm layer of 4,4',4"-tris(carbazol-9-yl)-triphenylamine (TCTA) was inserted between the TAPC and DPEPO layers to form a step-wise HTL and thus increased the hole injection. [32] The total thickness of the HTLs was fixed at 70 nm.…”

Section: Tadf Based Oled Fabricationmentioning

confidence: 99%

Design and Synthesis of Novel Phenothiazine‐Benzothiadiazine‐1,1‐dioxide Hybrid Organic Material for OLED Applications

et al. 2021

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In this study, yellow thermally activated delayed fluorescence (TADF) emitter PTZ-SA has been designed and synthesized by incorporating phenothiazine as donor and benzothiadiazine-1,1-dioxide as an acceptor. The molecule is also screened for aggregation induced emission in THF/Water system. PTZ-SA shows exceptionally high glass transition temperature (T g ) of 188 °C which clearly highlights good thermal stability of the material. The energy gap (ΔE ST ) between singlet (S1) and triplet (T1) excitons is sufficiently small (0.08 eV) for the reverse intersystem crossing. Yellow electroluminescence peak is observed at 568 nm with Commission Internationale de L'Eclairage coordinates of (0.44, 0.50). The external quantum efficiency of 4.2 % from PTZ-SA is achieved in yellow emitting OLED with turn on voltage of 5.1 V. Moreover, sufficiently high triplet energy of 2.5 eV and good film forming ability of PTZ-SA, encouraged us to study its electro-phosphorescent properties. Nevertheless, the red phosphorescent OLED device incorporating PTZ-SA dopped with a red emitter Ir(piq) 2 acac exhibited maximum external quantum efficiency, power efficiency and luminescence efficiency of 8.1 %, 7.2 lm W À 1 and 5.1 cd A À 1 , respectively.

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Triarylboryl-substituted carbazoles as bipolar host materials for efficient green phosphorescent organic light-emitting devices

Cited by 23 publications

References 39 publications

Facile Generation of Thermally Activated Delayed Fluorescence and Fabrication of Highly Efficient Non‐Doped OLEDs Based on Triazine Derivatives

Facile Generation of Thermally Activated Delayed Fluorescence and Fabrication of Highly Efficient Non‐Doped OLEDs Based on Triazine Derivatives

Dicyano‐Imidazole: A Facile Generation of Pure Blue TADF Materials for OLEDs

Design and Synthesis of Novel Phenothiazine‐Benzothiadiazine‐1,1‐dioxide Hybrid Organic Material for OLED Applications

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