Expanding the hole delocalization range in excited molecules for stable organic light-emitting diodes employing thermally activated delayed fluorescence

Zheng, Xinyuan; Cao, Fangyi; Wang, Chao; Tsuboi, Taijū; Zhu, Yunhui; Ai, Qi; Deng, Chao; Wang, Dan; Su, Liwu; Liu, Zhang; Zhang, Qisheng

doi:10.1039/d0tc01897j

Cited by 17 publications

(16 citation statements)

References 61 publications

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“…4), where BCz-o-TRZ (9-(2-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)-9'-phenyl-9H,9'H-3,3'-bicarbazole) and Ir(ppy)3 (fac-tris (2-phenylpyridine) iridium) were the bipolar transport materials with a small ΔEST and a classic green phosphor, respectively. 38,39 The device without tCzphB-Ph had a unique EL spectrum of Ir(ppy)3 with an FWHM value of 58 nm and CIE coordinates of (0.26, 0.64). The device achieved an EQE maximum of 20.0% and an EQE of 18.0% at a luminance of 10,000 cd/m 2 .…”

Section: Resultsmentioning

confidence: 99%

Toward a BT.2020 green emitter through a combined multiple resonance effect and multi-lock strategy

Liu

Zhu²,

Tsuboi

et al. 2022

Preprint

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Color-saturated green-emitting molecules with high Commission Internationale de L'Eclairage (CIE) y values have great potential applications for displays and imaging. In this study, we linked the outer phenyl groups in multiple-resonance (MR)-type blue-emitting B (boron)-N (nitrogen) molecules through bonding and spiro-carbon bridges, which resulted in planar and rigid green emitters with thermally activated delayed fluorescence. The MR effect and multiple interlocking strategy greatly suppressed the high-frequency vibrations in the molecules, which emit green light with a full-width at half-maximum of 14 nm and a CIE y value of 0.77 in cyclohexane. These were the purest green molecules with quantum efficiency and color purity that were comparable to the best quantum dots currently available. Doping these emitters into a traditional green-emitting phosphorescence organic light-emitting diode (OLED) endowed the device with a Broadcast Service Television 2020 color-gamut, 50% improved external quantum efficiency, and an extremely high luminescence of 4.6×105 cd/m2, making it the greenest and brightest OLED ever reported.

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Section: Resultsmentioning

confidence: 99%

Toward a BT.2020 green emitter through a combined multiple resonance effect and multi-lock strategy

Liu

Zhu²,

Tsuboi

et al. 2022

Preprint

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“…A small amount of the narrow bandgap coupling products could quench the emission from new molecules effectively. 62,85 As found in some TADF systems mentioned above, 15,[20][21][22][23] efficient and stable blue TADF OLEDs could be achieved by employing a TADF emitter with relatively large ΔE ST and long TADF lifetime. A possible explanation is that the S 1 state of most TADF molecules is a large-polarity CT state, that is, a diradical state.…”

Section: Degradation Mechanisms In Blue Tadf Oledsmentioning

confidence: 88%

“…Quite recently, Zheng et al 85 investigated the PL and EL properties of five efficient bluish-green TADF emitters with phenyltriazine acceptors and carbazole or indolo [2,3-b]carbazole donors. The relative EL stabilities of these emitters were consistent with the relative PL stabilities of these emitters in films.…”

Section: Degradation Mechanisms In Blue Tadf Oledsmentioning

confidence: 99%

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Degradation Mechanisms in Blue Organic Light-Emitting Diodes

et al. 2020

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An organic light-emitting diode (OLED) is required to exhibit long-time operation without degradation as an inorganic LED. Sufficiently long operation time has been demonstrated for green-and red-emitting OLEDs. However, a blue device that is important for full-color display and lighting exhibits a much shorter operational lifetime than the other color devices. The short lifetime is mainly attributed to the molecular dissociation and the defects and radical species formation through various unimolecular and bimolecular processes, including direct photolysis, exciton-exciton interaction, and exciton-polaron interaction, and so on. Different novel techniques of chemistry and physics have been employed for blue devices to suppress the degradation process induced by high-energy excitons. A deep understanding of the degradation mechanism is still needed for all three kinds of blue OLEDs employing fluorescence, phosphorescence, and thermally active delayed fluorescence. In this brief review, we introduce and discuss several degradation mechanisms for these three kinds of OLEDs.

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“…Due to their long luminescence lifetimes and large Stokes shift, these materials have been widely used in information anticounterfeiting, , information encryption, , bioimaging, optical sensing, , architectural decoration, etc. Nowadays, traditional TADF and RTP materials mainly focusing on inorganic compounds with rare earth elements, , pure organic compounds, , and noble-metal-containing compounds − suffer from some limitations, such as high toxicity, complex preparation processes, high costs, environmentally unfriendly nature, relatively short luminescence lifetimes, and low luminescence efficiency. − The above shortcomings largely limit their range of applications. Therefore, there is an urgent requirement for developing a new afterglow material to overcome these disadvantages.…”

Section: Introductionmentioning

confidence: 99%

Construction and Multifunctional Applications of Visible-Light-Excited Multicolor Long Afterglow Carbon Dots/Boron Oxide Composites

Sun

Cao

2021

ACS Sustainable Chem. Eng.

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Compared to ultraviolet light, visible light as an excitation light source has lower phototoxicity and deeper penetrability. This is of importance to explore the application of long afterglow materials with visible light as the excitation wavelength. In this work, multicolor long afterglow materials excited by visible light were prepared by embedding carbon dots (CDs) in boron oxide (B 2 O 3 ) and the formation of carbon−boron bonds, and the glassy state of B 2 O 3 during the heating process protected the triplet excitons from being quenched, thereby promoting the emission of long afterglow. In addition, some CDs/ B 2 O 3 composites show dual-mode afterglow emission with thermally activated delayed fluorescence (TADF) and roomtemperature phosphorescence (RTP) at the same time. These as-designed multicolor CDs/B 2 O 3 composites exhibit a long lifetime of 445.9 ms, a high afterglow quantum efficiency of 17.61%, and high stability. Meanwhile, the afterglow can be observed at room temperature by the naked eye and lasts for several seconds when the visible light is just switched off. These as-obtained CDs/B 2 O 3 composites with visible-light-excited multicolor long afterglow emission have shown potential in reversible ratiometric temperature sensing, latent fingerprint identification, information anticounterfeiting, and encryption.

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Expanding the hole delocalization range in excited molecules for stable organic light-emitting diodes employing thermally activated delayed fluorescence

Abstract:
The degradation in TADF OLEDs is found to be governed by the radical electrophilic substitutions between two charge-transfer (CT) excitons. Expanding the mean localization distance (RLOL) of hole in the CT state can improve device stability.

Cited by 17 publications

References 61 publications

Toward a BT.2020 green emitter through a combined multiple resonance effect and multi-lock strategy

Toward a BT.2020 green emitter through a combined multiple resonance effect and multi-lock strategy

Degradation Mechanisms in Blue Organic Light-Emitting Diodes

Construction and Multifunctional Applications of Visible-Light-Excited Multicolor Long Afterglow Carbon Dots/Boron Oxide Composites

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Expanding the hole delocalization range in excited molecules for stable organic light-emitting diodes employing thermally activated delayed fluorescence

Abstract: The degradation in TADF OLEDs is found to be governed by the radical electrophilic substitutions between two charge-transfer (CT) excitons. Expanding the mean localization distance (RLOL) of hole in the CT state can improve device stability.

Cited by 17 publications

References 61 publications

Toward a BT.2020 green emitter through a combined multiple resonance effect and multi-lock strategy

Toward a BT.2020 green emitter through a combined multiple resonance effect and multi-lock strategy

Degradation Mechanisms in Blue Organic Light-Emitting Diodes

Construction and Multifunctional Applications of Visible-Light-Excited Multicolor Long Afterglow Carbon Dots/Boron Oxide Composites

Contact Info

Product

Resources

About

Abstract:
The degradation in TADF OLEDs is found to be governed by the radical electrophilic substitutions between two charge-transfer (CT) excitons. Expanding the mean localization distance (RLOL) of hole in the CT state can improve device stability.