Perspective on carbazole-based organic compounds as emitters and hosts in TADF applications

Wex, Brigitte; Kaafarani, Bilal R.

doi:10.1039/c7tc02156a

Cited by 272 publications

(204 citation statements)

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“…[18][19][20][21][22] Regardingt he linear organic semiconductors, the bridge has as ignificant impacto nt he structuralp roperties (by notably rigidifying and flattening the molecular structure), which, in turn, modify the electronic properties. [18][19][20][21][22] Regardingt he linear organic semiconductors, the bridge has as ignificant impacto nt he structuralp roperties (by notably rigidifying and flattening the molecular structure), which, in turn, modify the electronic properties.…”

Section: Resultsmentioning

confidence: 99%

[4]Cyclo‐N‐ethyl‐2,7‐carbazole: Synthesis, Structural, Electronic and Charge Transport Properties

Lucas

Sicard

Jeannin

et al. 2019

Chemistry A European J

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Nanorings, which are macrocyclesp ossessing radially directed p-orbitalsh ave shown fantastic developmenti n the last ten years. Unravelling their unusuale lectronicp roperties has been one of the driving forces of this research field. However,a nd despite promising properties, their incorporationi no rganic electronic devices remains very scarce. In this work, we aim to contribute to bridge the gap between organice lectronics and nanorings by reporting the synthesis, the structurala nd electronic properties and the incorporation in an organic field-effect transistor (OFET) of ac yclic tetracarbazole, namely[ 4]cyclo-N-ethyl-2,7-carbazole( [4]C-Et-Cbz). The structural, photophysicala nd electrochemical properties have been compared to those of structurally related analogues [4]cyclo-9,9-diethyl-2,7-fluorene [4]C-diEt-F (with carbon bridges) and [8]-cycloparaphenylene [8]CPP (withouta ny bridge) in ordert os hed light on the impact of the bridging in nanorings. This work shows that nanorings can be used as an active layer in an OFET and provides a first benchmark in term of OFET characteristicsf or this type of molecules.

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Section: Resultsmentioning

confidence: 99%

[4]Cyclo‐N‐ethyl‐2,7‐carbazole: Synthesis, Structural, Electronic and Charge Transport Properties

Lucas

Sicard

Jeannin

et al. 2019

Chemistry A European J

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“…Non-doped OLEDs of these AIDF luminogens exhibit excellent luminance (ca. [1,3] However,like phosphorescent emitters,T ADF ones generally have to be dispersed into host matrices to alleviate concentration quenching. Non-doped OLEDs have merits of process simplicity and advanced stability relative to complicated doped devices that often encounter phase separation and insufficient energy transfer.…”

mentioning

confidence: 99%

“…Non-doped OLEDs have merits of process simplicity and advanced stability relative to complicated doped devices that often encounter phase separation and insufficient energy transfer. [1,3] However,like phosphorescent emitters,T ADF ones generally have to be dispersed into host matrices to alleviate concentration quenching. Forexam-ple,o rganic emitters with thermally activated delayed fluorescence (TADF) [1] are able to efficiently harvest both singlet and triplet excitons via reverse intersystem crossing (RISC) based on small energy splitting between lowest excited triplet state (T 1 )a nd lowest excited singlet state (S 1 ).…”

mentioning

confidence: 99%

“…However,most luminescent materials are unable to function efficiently in non-doped OLEDs because of severe concentration quenching and exciton annihilation. [1][2][3][4] Nevertheless,T ADF emitters still suffer from drastic efficiency roll-off at high voltages,which greatly delays their practical application. [2] They have shown remarkable electroluminescence (EL) performance comparable or even superior to those of expensive noble metal-containing phosphorescent materials.…”

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confidence: 99%

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High‐Performance Non‐doped OLEDs with Nearly 100 % Exciton Use and Negligible Efficiency Roll‐Off

et al. 2018

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Non-doped organic light-emitting diodes (OLEDs) possess merits of higher stability and easier fabrication than doped devices. However, luminescent materials with high exciton use are generally unsuitable for non-doped OLEDs because of severe emission quenching and exciton annihilation in neat films. Herein, we wish to report a novel molecular design of integrating aggregation-induced delayed fluorescence (AIDF) moiety within host materials to explore efficient luminogens for non-doped OLEDs. By grafting 4-(phenoxazin-10-yl)benzoyl to common host materials, we develop a series of new luminescent materials with prominent AIDF property. Their neat films fluoresce strongly and can fully harvest both singlet and triplet excitons with suppressed exciton annihilation. Non-doped OLEDs of these AIDF luminogens exhibit excellent luminance (ca. 100000 cd m ), outstanding external quantum efficiencies (21.4-22.6 %), negligible efficiency roll-off and improved operational stability. To the best of our knowledge, these are the most efficient non-doped OLEDs reported so far. This convenient and versatile molecular design is of high significance for the advance of non-doped OLEDs.

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“…TADF emitters are usually composed of electron donor (D) and acceptor (A) moieties, for example, with the D‐A or D‐π‐A type. Due to strong electron‐donating ability as well as stable and high excited triplet state, phenoxazine, carbazole, and triphenylamine have been reported to act as the D fragments, and electron‐deficient aromatic molecules such as triazine, 4‐benzoylpyridine, and diphenyl sulfone can be used as the A moieties. In addition, pyrimidine has also been proposed as an alternative A unit, owing to its electron‐deficient characteristics and facile functionalization .…”

Section: Introductionmentioning

confidence: 99%

Theoretical study on photophysical properties of a series of functional pyrimidine‐based organic light‐emitting diodes emitters presenting thermally activated delayed fluorescence

2019

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Issue concerning accurate prediction of the reverse intersystem crossing rate (kRISC) is critical for developing novel efficient thermally activated delayed fluorescence (TADF) materials. In this contribution, the kRISC rates from the lowest excited triplet T1 state to the lowest excited singlet S1 state were evaluated for five donor‐π‐acceptor‐type pyrimidine‐based TADF emitters using the semiclassical Marcus theory. Both the singlet‐triplet energy difference (ΔEST) and spin–orbit coupling (V) between the S1 and T1 states were investigated by performing the density functional theory (DFT) and time‐dependent density functional theory (TD‐DFT) calculations. In addition, their fluorescence emission wavelengths (λem) were also calculated at the TD‐DFT level. The predicted kRISC and λem values are found to reproduce well the available experimental findings. The present results reveal that the kRISC rates of molecules possessing the unsymmetrical diphenyl pyrimidine acceptor core are calculated to be slightly larger than those of their analogues with the symmetrical diphenyl pyrimidine. In addition, introducing two tert‐butyl groups into the 2,7‐positions of the donor moiety of the latter is also an effective method for increasing kRISC when designing TADF emitters. Such a difference is related to the nature of the T1 excited state. A more remarkable charge‐transfer (CT) contribution to the state can achieve a smaller ΔEST, leading to a more efficient RISC process, and consequently a shorter delayed fluorescence lifetime as observed experimentally. © 2019 Wiley Periodicals, Inc.

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Perspective on carbazole-based organic compounds as emitters and hosts in TADF applications

Abstract: Perspective covering carbazole-containing emitters and hosts for third generation TADF (thermally-activated delayed fluorescence) OLED technology along with computational benchmark studies.

Cited by 272 publications

References 200 publications

[4]Cyclo‐N‐ethyl‐2,7‐carbazole: Synthesis, Structural, Electronic and Charge Transport Properties

[4]Cyclo‐N‐ethyl‐2,7‐carbazole: Synthesis, Structural, Electronic and Charge Transport Properties

High‐Performance Non‐doped OLEDs with Nearly 100 % Exciton Use and Negligible Efficiency Roll‐Off

Theoretical study on photophysical properties of a series of functional pyrimidine‐based organic light‐emitting diodes emitters presenting thermally activated delayed fluorescence

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