Boron‐Based Multi‐Resonance TADF Emitter with Suppressed Intermolecular Interaction and Isomer Formation for Efficient Pure Blue OLEDs

Cheon, Hyung Jin; Shin, Youn-Seob; Park, Noh-Hwal; Lee, Jeong‐Hwan; Kim, Yun‐Hi

doi:10.1002/smll.202107574

Cited by 59 publications

(24 citation statements)

References 85 publications

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“…Furthermore, we investigated the theoretically achievable EQE values of the devices using optical simulations. The horizontal dipole ratios (HDRs) of the emitters were precisely checked using thin films comprising mCBP:5 wt % doped emitters (Figure e). , The emitters exhibited similar D–A configurations such that they had similar HDR values of 72 ± 2% for D1 , and 70 ± 2% for D2 and D3 , respectively. Using the PLQYs and HDRs of the emitters and TADF-OLED structures, we performed optical simulations, and the results are shown in Figure f as a contour map.…”

Section: Resultsmentioning

confidence: 99%

Impact of π-Expanded Boron-Carbonyl Hybrid Acceptors on TADF Properties: Controlling Local Triplet Excited States and Unusual Emission Tuning

Istiqomah

Jang

Lee

et al. 2023

ACS Appl. Mater. Interfaces

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Three donor−acceptor-type thermally activated delayed fluorescence (TADF) emitters (PXZBAO (1), PXZBTO (2), and PXZBPO (3)) comprising a phenoxazine (PXZ) donor and differently π-expanded boroncarbonyl (BCO) hybrid acceptor units are proposed. The emitters exhibit red (1) to orange (3) emissions with an increase in the π-expansion in the BCO acceptors. The control of the strength of local aromaticity for the BCO unit and the corresponding LUMO level is attributed to inducing the unusual emission color shifts. The photoluminescence quantum yield and delayed fluorescence lifetime of the emitters are also adjusted by the π-expansion. Notably, although 1 possesses a 3 nπ* state in the acceptor unit as a local triplet excited state ( 3 LE, T 2 ), the T 2 states of 2 and 3 mainly comprise a 3 ππ* state in the acceptor. Consequently, all of the emitters exhibit strong spin−orbit coupling between their T 2 and excited singlet (S 1 ) states, leading to a fast reverse intersystem crossing with rate constants of ∼10 6 s −1 . By employing the emitters as dopants, we realize efficient red-to-orange TADF-OLEDs. Maximum external quantum efficiencies of 17.7% for the yellowish-orange (3), 15.5% for the orange (2), and 13.9% for the red (1) devices are achieved, and the values are very close to the theoretical limit predicted from the optical simulation.

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Section: Resultsmentioning

confidence: 99%

Impact of π-Expanded Boron-Carbonyl Hybrid Acceptors on TADF Properties: Controlling Local Triplet Excited States and Unusual Emission Tuning

Istiqomah

Jang

Lee

et al. 2023

ACS Appl. Mater. Interfaces

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“…Kim et al reported a new pure blue emitter named mBP‐DABNA‐Me , wherein xylene and meta‐phenyl groups were introduced into the DABNA core to effectively suppress aggregation‐caused quenching and prevent the isomer formation in the reaction. [ 100 ] The mBP‐DABNA‐Me manifested pure blue emission with λ PL of 464 nm and FWHM of 28 nm in the toluene solution. Notably, the doped film exhibited only a 3 nm redshift compared to the solution attributed to the suppressed π–π interactions, and as a result, the PLQY yielded in 97%.…”

Section: Blue/deep‐blue Mr‐tadf Emittersmentioning

confidence: 99%

Boron‐Based Narrowband Multiresonance Delayed Fluorescent Emitters for Organic Light‐Emitting Diodes

Konidena

Naveen

2022

Advanced Photonics Research

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Recently, the exploration of boron (B)/heteroatom-embedded polycyclic nanographites featuring multiresonance thermally activated delayed fluorescence (MR-TADF) garners astonishing attention to promote the advancement of organic light-emitting diodes (OLEDs). Contrary to the traditional donor-acceptor (D-A)-type TADF emitters, the MR-TADF emitters manifest narrowband emission with full width at half maximum (FWHM ≤ 40 nm) and superior photoluminescence quantum yield (PLQY) coupled with the small singlet-triplet energy splitting, which appeal their potential as promising candidates in fabricating efficient OLEDs. Growingly, MR-TADF emitters deliver benchmark device performance comparable to the conventional TADF/phosphorescent emitters. However, they are suffering from the major drawbacks such as difficult to realize full-color emitters, slow exciton upconversion dynamics, aggregationcaused emission quenching, severe efficiency roll-off, and poor operational lifetime, which jeopardizes their practical applicability. Herein, a comprehensive review on B-based MR-TADF emitters reported till date is presented, focusing on the different design strategies documented for circumventing the aforementioned shortcomings. This review is divided into several subgroups based on the emission color of the materials to draw the attention of organic electronics community toward constructing efficient full-color MR-OLEDs. Finally, challenges and opportunities in the MR-TADF emitters are discussed.

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“…In order to achieve high-color purity deep-blue emission, narrowband chromophores with electroluminescent (EL) emission peaks at 460 ± 5 nm are required. − At the same emission peak, the narrower FWHM manifests a smaller CIE y value (and a higher current efficiency/CIE y index) and relatively lower excited state (S 1 ) energies due to the bathochromic shift for the spectral onset. However, owing to the difficulty in managing large bandgap chromophores and maintaining efficient radiative emissions, molecular design strategies for color-saturated deep-blue and high photoluminescence quantum yield (PLQY) emitters are still rare and challenging. − …”

Section: Introductionmentioning

confidence: 99%

Toward Narrowband and Efficient Blue Fluophosphors by Locking the Stretching Vibration of Indolocarbazole Skeletons

Wang

Yan

Qi-shen

et al. 2023

ACS Appl. Mater. Interfaces

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Developing efficient and color-saturated deep-blue emitting molecules with small Commission Internationale de L’Eclairage (CIE) y values is challenging and has great potential for wide-color gamut displays. Herein, we introduce an intramolecular locking strategy to restrain molecular stretching vibrations of the emission spectral broadening. By cyclizing rigid fluorenes and connecting electron-donating groups to the indolo[3,2,1-jk]-indolo[1′,2′,3′:1,7]indolo[2,3-b]carbazole (DIDCz) framework, the in-plane swing of peripheral bonds and stretching vibrations of the indolocarbazole skeleton are restricted due to an increased steric hindrance from cyclized groups and diphenylamine auxochromophores. As a result, reorganization energies at the high-frequency region (1300–1800 cm–1) are reduced, realizing pure blue emission with a small full-width-at-half-maximum (FWHM) of 30 nm by suppressing shoulder peaks of polycyclic aromatic hydrocarbon (PAH) frameworks. The fabricated bottom-emitting organic light-emitting diode (OLED) exhibits an efficient external quantum efficiency (EQE) of 7.34% and deep-blue coordinates of (0.140, 0.105) at a high brightness of 1000 cd/m2. The FWHM of the electroluminescent spectrum is only 32 nm, which is one of the narrowest electroluminescent emissions among the reported intramolecular charge transfer fluophosphors. Our current findings provide a new molecular design strategy to conceive efficient and narrowband emitters with small reorganization energies.

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Boron‐Based Multi‐Resonance TADF Emitter with Suppressed Intermolecular Interaction and Isomer Formation for Efficient Pure Blue OLEDs

Cited by 59 publications

References 85 publications

Impact of π-Expanded Boron-Carbonyl Hybrid Acceptors on TADF Properties: Controlling Local Triplet Excited States and Unusual Emission Tuning

Impact of π-Expanded Boron-Carbonyl Hybrid Acceptors on TADF Properties: Controlling Local Triplet Excited States and Unusual Emission Tuning

Boron‐Based Narrowband Multiresonance Delayed Fluorescent Emitters for Organic Light‐Emitting Diodes

Toward Narrowband and Efficient Blue Fluophosphors by Locking the Stretching Vibration of Indolocarbazole Skeletons

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