Efficient donor-acceptor-donor borylated compounds with extremely small ΔEST for thermally activated delayed fluorescence OLEDs

Tsai, Chih-Chieh; Huang, Wen-Chin; Chih, Hsin-Yun; Hsh, Yu-Chien; Liao, Chia-Wei; Lin, Chi‐Hui; Kang, Yu-Xuan; Chang, Chih-Hao; Chang, Yuan Jay; Lu, Chin‐Wei

doi:10.1016/j.orgel.2018.09.023

Cited by 33 publications

(17 citation statements)

References 60 publications

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“…For molecules to achieve efficient TADF, a subtle linkage of electron-donor and -acceptor moieties can lead to limited overlaps between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of a chromophore, giving a sufficiently small (<0.2 eV) singlet–triplet energy gap (Δ E ST ) to enable rISC. 6,7 Consequently, the up-conversion mechanism could be realized with the aid of environmental thermal energy to give highly efficient TADF-based OLEDs. Alternatively, blending judiciously selected donor (D) and acceptor (A) molecules can result in the formation of exciplex via intermolecular charge transfer.…”

Section: Introductionmentioning

confidence: 99%

Harnessing bipolar acceptors for highly efficient exciplex-forming systems

et al. 2022

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Section: Introductionmentioning

confidence: 99%

Harnessing bipolar acceptors for highly efficient exciplex-forming systems

et al. 2022

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“…1.0 × 10 4 M –1 cm –1 ) and similar spectral characteristics and negligible solvent effects, which can be attributed to the spin-allowed acceptor-centered π → π* electronic transition of the dicyano-imidazole unit. The relatively low-intensity broadband at 290–350 nm can be presumably assigned to the combination of π → π* and n → π* electronic transitions of carbazole and intramolecular CT (ICT) from the carbazole fragment to the dicyano-imidazole moiety. − Compared to imM- o -Cz and imM- m -Cz , the conjugate system is more continuous because of the better planarity of the structure of imM- p -Cz , thus showing a higher intensity of ICT absorption. In addition, the corresponding optical energy band gaps evaluated using the absorption onset for imM- o -Cz , imM- m -Cz , and imM- p -Cz were 3.59, 3.54, and 3.40 eV, respectively.…”

Section: Resultsmentioning

confidence: 99%

Dicyano-Imidazole-Based Host Materials Possessing a Balanced Bipolar Nature To Realize Efficient OLEDs with Extremely High Luminance

Shao

Lin

et al. 2020

J. Phys. Chem. C

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Most phosphorescent devices suffer from severe triplet−triplet annihilation (TTA), and the efficiency recording at high luminance is much lower than that at low luminance, making the practicality worse than expected. In this study, a series of donor−acceptor (D−A) molecules consisting of dicyano-imidazole and phenylcarbazole were synthesized and applied to the host materials. For electroluminescence applications, imM-m-Cz-based green-emitting organic light-emitting diodes show a maximum luminance of 1.68 × 10 5 cd m −2 at 11.2 V, which is 20% higher than that of the benchmark host 4,4′-bis(N-carbazolyl)-1,1′-biphenyl at 13.4 V; in addition, the turn-on voltage (V on ) is only 2.3 V. In terms of hole and electron mobility, imM-m-Cz shows one of the most balanced carrier mobilities in the reported literature (electron and hole mobilities of 3.64 × 10 −5 and 4.23 × 10 −5 cm 2 V −1 s −1 , respectively). The balanced carrier mobility can help expand the recombination region and thus reduce the formation of TTA. Furthermore, the high maximum luminance of about 2.80 × 10 5 cd m −2 obtained in an imM-m-Cz-based tandem device demonstrates a sufficiently high current density/luminance, and the peak efficiency achieves an even higher efficiency of 40.6% (1.51 × 10 5 cd A −1 and 98.6 lm W −1 ), which is among the highest reported properties based on imidazole-based host materials. Combining the balanced carrier mobility with the proper device design in this study, the efficiency roll-off under high luminance can be greatly reduced, and the practicality of the resulting phosphorescent device can be significantly improved.

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“…33 Various donor and acceptor groups were designed to enhance charge transfer in TADF luminophores. The most frequently used donor moieties are diphenylamine, 2,34,35 carbazole, 23,[36][37][38][39][40][41][42][43][44] acridine, 17,20,45 and phenoxazine derivatives, [46][47][48][49] while the most common acceptor units include boron, [50][51][52][53][54][55][56][57][58] sulfone, 23,25,41 and benzophenone derivatives (Figure 2). 20,24,59,60 However, TADF systems are not limited to these building blocks, other interesting frameworks were designed such as cyanobenzenes, 59 triazines, 61 oxadiazoles, 31 sulfones, 62 and spiro derivatives.…”

Section: Introductionmentioning

confidence: 99%

A Computational Descriptor Analysis on Excited State Behaviours of a Series of TADF and Non-TADF Compounds

Ulukan

Baş

Ozek

et al. 2021

Preprint

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The thermally activated delayed fluorescence (TADF) behaviours of seventeen organic TADF emitters and two non-TADF chromophores bearing various donor and acceptor moieties were investigated, focusing on their torsion angles, singlet-triplet gap (ΔEST), spin orbit couplings (SOC) and topological ΦS index. Electronic structure calculations were performed in the framework of the Tamm-Dancoff approximation (TDA) allowing to characterize reverse intersystem crossing (RISC) probability between the S1 and T1 states. In addition, experimental ΔEST data were taken into account to choose the most appropriate functional and basis set, while absorption spectra were obtained by considering vibrational and dynamical effects through a Wigner sampling of the ground state equilibrium regions. Examining all the parameters obtained in our computational study, we rationalized the influence of electron-donating and electron-accepting groups and the effects of geometrical factors, namely torsion angles, on a wide class of diverse compounds ultimately providing an easy and computationally effective protocol to assess TADF efficiencies.

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Efficient donor-acceptor-donor borylated compounds with extremely small ΔEST for thermally activated delayed fluorescence OLEDs

Cited by 33 publications

References 60 publications

Harnessing bipolar acceptors for highly efficient exciplex-forming systems

Harnessing bipolar acceptors for highly efficient exciplex-forming systems

Dicyano-Imidazole-Based Host Materials Possessing a Balanced Bipolar Nature To Realize Efficient OLEDs with Extremely High Luminance

A Computational Descriptor Analysis on Excited State Behaviours of a Series of TADF and Non-TADF Compounds

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