Fundamental functions of peripheral and core pyridine rings in a series of bis-terpyridine derivatives for high-performance organic light-emitting devices

Watanabe, Yuichiro; Yoshioka, Ryo; Sasabe, Hiroyuki; Kamata, Toshihide; Katagiri, Hiroshi; Yokoyama, Daisuke; Kido, Junji

doi:10.1039/c6tc02631a

Cited by 29 publications

(11 citation statements)

References 58 publications

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“…Pyridine rings at the ends of the molecule were expected to undergo intermolecular weak H‐bond interactions with neighboring molecules in the films. In contrast, the inner pyridine rings were expected to exhibit planarization of the molecular structure, which reduced the steric hindrance of the hydrogen atoms located at ortho‐ positions of the aromatic rings and introducing intramolecular H‐bonds (Figure B) . The molecular orientations were carefully validated and analyzed by two different methods, GIWAXD and VASE.…”

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confidence: 99%

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Control of Molecular Orientation in Organic Semiconductor Films using Weak Hydrogen Bonds

et al. 2019

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Use of the intrinsic optoelectronic functions of organic semiconductor films has not yet reached its full potential, mainly because of the primitive methodology used to control the molecular aggregation state in amorphous films during vapor deposition. Here, a universal molecular engineering methodology is presented to control molecular orientation; this methodology strategically uses noncovalent, intermolecular weak hydrogen bonds in a series of oligopyridine derivatives. A key is to use two bipyridin‐3‐ylphenyl moieties, which form self‐complementary intermolecular weak hydrogen bonds, and which do not induce unfavorable crystallization. Another key is to incorporate a planar anisotropic molecular shape by reducing the steric hindrance of the core structure for inducing π–π interactions. These synergetic effects enhance horizontal orientation in amorphous organic semiconductor films and significantly increasing electron mobility. Through this evaluation process, an oligopyridine derivative is selected as an electron‐transporter, and successfully develops highly efficient and stable deep‐red organic light‐emitting devices as a proof‐of‐concept.

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“…First, we compared three types of molecules, 1 – 3 , have two terpyridine moieties which is known as electron‐acceptor units for OLEDs . Notably, these molecules had different peripheral pyridine rings.…”

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Control of Molecular Orientation in Organic Semiconductor Films using Weak Hydrogen Bonds

et al. 2019

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“…In solution, there are two absorption peaks at 297 and 308 nm, as shown in Table 1 , which are attributed to the π–π* transition of the fluorene units in spirobifluorene . Another two absorption peaks of 254 and 280 nm are ascribed to the TPY . The strong absorption band above 310 nm suggests that there is electronic coupling between the spirobifluorene and the two TPY components .…”

Section: Resultsmentioning

confidence: 97%

“…We once reported a deep‐blue emitter of 2,7‐di(2,2′:6′,2″‐terpyridin‐4‐yl)‐9,9‐dioctyl‐9H‐fluorene (DTPF) by using TPY as the acceptor to improve its ET property . Recently, Kido et al investigated a series of TPY isomers, achieving 23.5% of a maximum external quantum efficiency (η ext, max ) in green PhOLED. To further improve the thermal stability of DTPF, a rigid twisted spirobifluorene could be introduced to replace fluorene .…”

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confidence: 99%

Long‐Lived and Highly Efficient TADF‐PhOLED with “(A)_n–D–(A)_n” Structured Terpyridine Electron‐Transporting Material

Bian

Zhang

Wang³

et al. 2018

Adv Funct Materials

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The electron-transporting material (ETM) is one of the key factors to determine the efficiency and stability of organic light-emitting diodes (OLEDs). A novel ETM with a "(Acceptor) n -Donor-(Acceptor) n " ("(A) n -D-(A) n ") structure, 2,7-di([2,2′:6′,2″-terpyridin]-4′-yl)-9,9′-spirobifluorene (27-TPSF), is synthesized by combining electron-withdrawing terpyridine (TPY) moieties and rigid twisted spirobifluorene, in which the TPY moieties facilitate electron transport and injection while the spirobifluorene moiety ensures high triplet energy (T 1 = 2.5 eV) as well as enhances glass transition temperature (T g = 195 °C) for better stability. By using tris[2-(p-tolyl)pyridine]iridium(III) (Ir(mppy) 3 ) as the emitter, the 27-TPSF-based device exhibits a maximum external quantum efficiency (η ext, max ) of 24.5%, and a half-life (T 50 ) of 121, 6804, and 382 636 h at an initial luminance of 10 000, 1000, and 100 cd m −2 , respectively, which are much better than the commercialized ETM of 9,10-bis(6-phenylpyridin-3-yl)anthracene (DPPyA). Furthermore, a higher efficiency, a η ext, max of 28.2% and a maximum power efficiency (η PE , max ) of 129.3 lm W −1 , can be achieved by adopting bis(2-phenylpyridine)iridium(III) (2,2,6,6-tetramethylheptane-3,5-diketonate) (Ir(ppy) 2 tmd) as the emitter and 27-TPSF as the ETM. These results indicate that the derivative of TPY to form "(A) n -D-(A) n " structure is a promising way to design an ETM with good comprehensive properties for OLEDs.

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“…For compound NN , 1% transmittance photoluminescence was too weak to measure, partly due to the pyridine ring of NN. [ 40 ]…”

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New bis‐photochromic compounds based on diarylimidazoles: Synthesis and multistimuli‐responsive optical properties

Song

Zhu

et al. 2020

Luminescence

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Three new bis‐photochromic molecules containing two 4,5‐diarylimidazole units were synthesized and characterized. We investigated their photophysical properties and pH response characteristics in acetonitrile solutions and polymethylmethacrylate (PMMA) membranes. All compounds displayed significant pH responses for the imidazole ring in the molecular structure, which could be potentially used as pH probes. Under ultraviolet light, these compounds show photochromism and ‘turn‐off’ fluorescence properties either in solution or in PMMA film. The mechanism of this phenomenon may be due to photoisomerization, that is the conversion of the 4,5‐diarylimidazole units open‐ring form to the closed‐ring form. Moreover, such systems as logic gates, high density (3D) data storage systems and optical equivalents of field‐effect transistors are considered necessary for optical computing.

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Fundamental functions of peripheral and core pyridine rings in a series of bis-terpyridine derivatives for high-performance organic light-emitting devices

Abstract: In this study, we comprehensively investigated a series of bis-terpyridine isomers, n-TerPyB, as optoelectronic materials.

Cited by 29 publications

References 58 publications

Control of Molecular Orientation in Organic Semiconductor Films using Weak Hydrogen Bonds

Control of Molecular Orientation in Organic Semiconductor Films using Weak Hydrogen Bonds

Long‐Lived and Highly Efficient TADF‐PhOLED with “(A)_n–D–(A)_n” Structured Terpyridine Electron‐Transporting Material

New bis‐photochromic compounds based on diarylimidazoles: Synthesis and multistimuli‐responsive optical properties

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Fundamental functions of peripheral and core pyridine rings in a series of bis-terpyridine derivatives for high-performance organic light-emitting devices

Abstract: In this study, we comprehensively investigated a series of bis-terpyridine isomers, n-TerPyB, as optoelectronic materials.

Cited by 29 publications

References 58 publications

Control of Molecular Orientation in Organic Semiconductor Films using Weak Hydrogen Bonds

Control of Molecular Orientation in Organic Semiconductor Films using Weak Hydrogen Bonds

Long‐Lived and Highly Efficient TADF‐PhOLED with “(A)n–D–(A)n” Structured Terpyridine Electron‐Transporting Material

New bis‐photochromic compounds based on diarylimidazoles: Synthesis and multistimuli‐responsive optical properties

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Long‐Lived and Highly Efficient TADF‐PhOLED with “(A)_n–D–(A)_n” Structured Terpyridine Electron‐Transporting Material