Spiro[fluorene-9,9‘-thioxanthene] core based host materials for thermally activated delayed fluorescence devices

Li, Yunchuan; Wang, Zhiheng; Cai, Xinyi; Liu, Kunkun; Dong, Jianqiao; Chang, Shuai; Su, Shi‐Jian

doi:10.1016/j.dyepig.2018.12.001

Cited by 11 publications

(8 citation statements)

References 43 publications

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“…However, more studies are required to verify if this property is produced by the synthesis method, or by the structure of the oligomer under study. It is known that fluorene-containing materials are widely studied in optoelectronics because of the planarity and high conjugation promoted in the molecule [ 30 , 31 ].…”

Section: Resultsmentioning

confidence: 99%

Mechanosynthesis of Photochromic Oligophenyleneimines: Optical, Electrochemical and Theoretical Studies

et al. 2019

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In this work, two oligophenyleneimines type pentamers with terminal aldehydes, designated as DAFCHO (4,4′-((((((2,5-bis(octyloxy)-1,4-phenylene)bis(methanylylidene))bis(azanyl ylidene))bis(9H-fluorene-7,2-diyl))bis(azanylylidene))bis(methanylylidene))bis(2,5-bis(octyloxy) benzaldehyde)) and FDACHO (4,4′-((((((2,5-bis(octyloxy)-1,4-phenylene)bis(methanylylidene))bis (azanylylidene))bis(4,1-phenylene))bis(azanylylidene))bis(methanylylidene))bis(2,5-bis(octyloxy) benzaldehyde)) were synthesized by mechanochemistry method using 2,5-bis(octyloxy) terephtal aldehyde and 2,7-diaminofluorene or 1,4-phenylenediamine. All compounds were spectroscopically characterized using 1H and 13C-NMR, FT-IR and mass spectrometry MALDITOF. The optical properties of the compounds were analyzed by UV-vis spectroscopy using different solvents. We observed that DAFCHO and FDACHO exhibit interesting photochromic properties when they are dissolved in chloroform and exposed to sunlight for 3, 5 and 10 min. The value of the energy band gap was calculated from the absorption spectra without irradiation Egap(optical). It was 2.50 eV for DAFCHO in chloroform solution, and it decreased to 2.34 eV when it is in films. For FDACHO, it was 2.41 eV in solution and 2.27 eV in film. HOMO (Highest Occupied Molecular Orbital), LUMO (Lowest Unoccupied Molecular Orbital) and Egap(electrochemical) values were obtained by electrochemical studies. The results indicate that the compounds can be considered as organic semiconductors since their values are 2.35 eV for DAFCHO and 2.06 eV for FDACHO. The structural and electronic properties of the compounds were corroborated with a DFT (Density Functional Theory) study.

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Section: Resultsmentioning

confidence: 99%

Mechanosynthesis of Photochromic Oligophenyleneimines: Optical, Electrochemical and Theoretical Studies

et al. 2019

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“…Another interesting study, reported by Su and co-workers, [110] concerned the independence of EL spectra of TADF emitter (4CzIPN) on the host polarity. In this study, the author reported four new host materials of Cz-S, 2Cz-S, Cz-SO2, and 2Cz-SO2, which were designed based on the spiro[fluorene-9,9′thioxanthene] core.…”

Section: Wwwadvopticalmatdementioning

confidence: 99%

Host‐Dopant Interaction between Organic Thermally Activated Delayed Fluorescence Emitter and Host Material: Insight into the Excited State

et al. 2021

Advanced Optical Materials

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rapidly, and the products based on OLEDs including smartphones, televisions, monitors, etc. are being commercialized.The utilization mechanism of the excitons determines the quantum efficiency of the devices. [13][14][15] OLEDs based on the conventional fluorescent materials can only harvest the singlet excitons for light emission, which results in an upper limit of only 25% for internal quantum efficiency (IQE). The phosphorescent OLEDs incorporating transition metals into the molecular framework of organic emitters represent a huge breakthrough, which demonstrated an IQE of nearly 100%. [16,17] However, phosphorescent emitters contain expensive transition metals, which increases the fabrication costs of the devices and limits their large-scale applications despite the high efficiency. Besides, the toxicity of heavy atoms is also a bothering issue. Thus, novel emission mechanisms are needed to improve both the efficiency and the cost issue. In this context, triplet-triplet annihilation (TTA, also known as P-type delayed fluorescence), [18] hybridized locally and charge transfer (HLCT, also known as the "hot exciton" mechanism), [19][20][21][22] and thermally activated delayed fluorescence (TADF) [23][24][25] are promising. Among them, TADF represents a successful mechanism for realizing high IQE up to 100% (Figure 1). In recent years, TADF emitters based on the multiresonance (MR-TADF) concept have drawn much research attention, which offer a perfect solution to achieving both high efficiency and high color purity. [1,3,6,26,27] Besides, TADF can be realized in purely organic emitters, which is merit for low-cost devices. In the TADF mechanism, the T 1 state can be converted to the S 1 state through a reserve intersystem crossing (RISC) facilitated by a small S 1 -T 1 energy gap (ΔE ST ). The fluorescence resulting from the S 1 on charge recombination is defined as prompt fluorescence with a short lifetime, while the fluorescence originating from the S 1 that is up converted from the T 1 state is defined as the delayed fluorescence with a long lifetime.TADF emitters are typically doped into a suitable organic matrix to address the quenching effects such as concentration quenching, triplet-triplet annihilation, singlet-triplet annihilation (STA), and triplet-polaron annihilation (TPA) to enhance the device efficiency and stability. [28][29][30][31][32][33] Thus, both host materials Organic light-emitting diodes (OLEDs) represent one of the most promising technologies for future displays and lighting sources, which have received extensive research attention. Purely organic thermally activated delayed fluorescence (TADF) emitters offer obvious advantages, including high efficiencies and low costs, and they are typically doped in host materials to achieve optimal device efficiencies. TADF emitters typically feature intramolecular charge transfer characteristics, and their excited states properties are sensitive to local environment, giving the implication that host materials can finely tune their emission properties...

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“…9,10 Based on the above strategies, many small molecule TADF host materials have been designed for high-efficiency OLEDs. [11][12][13] For instance, Li et al reported a series of new spiro[fluorene-9,9 0 -thioxanthene] core-based wide-energy-gap compounds as host materials for the TADF emitter (4CzIPN), and a maximum current efficiency (CE) of 52.1 cd A À1 and maximum external quantum efficiency (EQE) of 16.5% were achieved. 12 However, most of the small molecule TADF materials are easy to crystallize, which leads to poor film formation and low wet processing efficiency.…”

Section: Introductionmentioning

confidence: 99%

“…[11][12][13] For instance, Li et al reported a series of new spiro[fluorene-9,9 0 -thioxanthene] core-based wide-energy-gap compounds as host materials for the TADF emitter (4CzIPN), and a maximum current efficiency (CE) of 52.1 cd A À1 and maximum external quantum efficiency (EQE) of 16.5% were achieved. 12 However, most of the small molecule TADF materials are easy to crystallize, which leads to poor film formation and low wet processing efficiency. Thus, beside the above basic requirements, an excellent host for a solutionprocessable device put forward high demands for molecular design, especially the film-forming properties.…”

Section: Introductionmentioning

confidence: 99%

Benzonitrile-based AIE polymer host with a simple synthesis process for high-efficiency solution-processable green and blue TADF organic light emitting diodes

Zhou¹,

Zhang²,

Cao³

et al. 2022

J. Mater. Chem. C

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Spiro[fluorene-9,9‘-thioxanthene] core based host materials for thermally activated delayed fluorescence devices

Cited by 11 publications

References 43 publications

Mechanosynthesis of Photochromic Oligophenyleneimines: Optical, Electrochemical and Theoretical Studies

Mechanosynthesis of Photochromic Oligophenyleneimines: Optical, Electrochemical and Theoretical Studies

Host‐Dopant Interaction between Organic Thermally Activated Delayed Fluorescence Emitter and Host Material: Insight into the Excited State

Benzonitrile-based AIE polymer host with a simple synthesis process for high-efficiency solution-processable green and blue TADF organic light emitting diodes

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