Multiple‐Resonance Extension and Spin‐Vibronic‐Coupling‐Based Narrowband Blue Organic Fluorescence Emitters with Over 30% Quantum Efficiency

Advanced Materials, Journal Year: 2022, Volume and Issue: 34(33)

Published: June 28, 2022

Achieving narrow-bandwidth emission and high external quantum efficiency (EQE) simultaneously is a challenge for next-generation blue-emitting organic light-emitting diodes (OLEDs). In this study, novel multiple-resonance thermally activated delayed fluorescence (MR-TADF) emitters are developed by fusing an indolocarbazole unit with two carbazole skeletons using para-oriented nitrogen atoms. The resulting rigid planar π-system without electron-accepting atoms exhibits pure blue photoluminescence at 470 nm, reaching 100% yield full-width-at-half-maximum (FWHM) of 25 nm. Higher-level chemistry calculations confirm MR effect within the extended π-conjugation enhanced triplet-to-singlet crossover (104 s-1 ) through reduced energy gap (ΔEST coupled large spin-vibronic coupling mediated low-lying triplet excited states. An OLED fabricated MR-TADF emitter CIE color coordinates (0.12, 0.16) record EQE 30.9% small FWHM 23 With further optimization device structure, 33.8% achieved additional outcoupling enhancements owing to near-perfect horizontal alignment emitting dipoles.

Language: Английский

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Diindolocarbazole – achieving multiresonant thermally activated delayed fluorescence without the need for acceptor units

Materials Horizons, Journal Year: 2022, Volume and Issue: 9(3), P. 1068 - 1080

Published: Jan. 1, 2022

In this work we present a new multi-resonance thermally activated delayed fluorescence (MR-TADF) emitter paradigm, demonstrating that the structure need not require presence of acceptor atoms. Based on an in silico design, compound DiICzMes4 possesses red-shifted emission, enhanced photoluminescence quantum yield, and smaller singlet-triplet energy gap, ΔEST, than parent indolocarbazole induces MR-TADF properties. Coupled cluster calculations accurately predict magnitude ΔEST when optimized singlet triplet geometries are used. Slow yet optically detectable reverse intersystem crossing contributes to low efficiency organic light-emitting diodes using as emitter. However, used terminal combination with TADF assistant dopant within hyperfluorescence device architecture, maximum external efficiencies up 16.5% were achieved at CIE (0.15, 0.11). This represents one bluest hyperfluorescent devices reported date. Simultaneously, recognising emitters do atoms reveals unexplored frontier materials where greater performance may be discovered.

Language: Английский

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Robust Luminescent Molecules with High‐Level Reverse Intersystem Crossing for Efficient Near Ultraviolet Organic Light‐Emitting Diodes

Angewandte Chemie International Edition, Journal Year: 2022, Volume and Issue: 61(10)

Published: Jan. 4, 2022

Organic light-emitting diodes (OLEDs) radiating near ultraviolet (NUV) light are of high importance but rarely reported due to the lack robust organic short-wavelength emitters. Here, we report a short π-conjugated molecule (POPCN-2CP) with thermal and morphological stabilities strong NUV photoluminescence. Its neat film exhibits an electroluminescence (EL) peak at 404 nm maximum external quantum efficiency (ηext,max ) 7.5 % small roll-off. The doped films POPCN-2CP in both non-polar polar hosts wide doping concentration range (10-80 wt%) achieve high-purity (388-404 nm) excellent ηext,max s up 8.2 %. high-level reverse intersystem crossing improves exciton utilization accounts for superb s. can also serve as efficient host blue fluorescence, thermally activated delayed fluorescence phosphorescence emitters, providing EL performance via Förster energy transfer.

Language: Английский

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Narrowband Organic Afterglow via Phosphorescence Förster Resonance Energy Transfer for Multifunctional Applications

Advanced Materials, Journal Year: 2023, Volume and Issue: 35(36)

Published: June 30, 2023

Achieving multicolor organic afterglow materials with narrowband emission and high color purity is important in various optoelectronic fields but remains a great challenge. Here, an efficient strategy presented to obtain via Förster resonance energy transfer from long-lived phosphorescence donors fluorescence acceptors polyvinyl alcohol matrix. The resulting exhibit full width at half maximum (FWHM) as small 23 nm the longest lifetime of 721.22 ms. Meanwhile, by pairing appropriate acceptors, ranging green red photoluminescence quantum yield 67.1% are achieved. Moreover, given their long luminescence lifetime, purity, flexibility, potential applications demonstrated high-resolution displays dynamic quick information identification low-light conditions. This work provides facile approach for developing well expands features afterglow.

Language: Английский

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A review of fused-ring carbazole derivatives as emitter and/or host materials in organic light emitting diode (OLED) applications

Materials Chemistry Frontiers, Journal Year: 2023, Volume and Issue: 7(19), P. 4304 - 4338

Published: Jan. 1, 2023

This review focuses on fused-ring carbazole derivatives, their molecular design, electronic and photophysical properties, applications as the emitter and/or host material in organic light emitting diodes (OLEDs).

Language: Английский

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Suppression of Dexter transfer by covalent encapsulation for efficient matrix-free narrowband deep blue hyperfluorescent OLEDs

Nature Materials, Journal Year: 2024, Volume and Issue: 23(4), P. 519 - 526

Published: March 13, 2024

Abstract Hyperfluorescence shows great promise for the next generation of commercially feasible blue organic light-emitting diodes, which eliminating Dexter transfer to terminal emitter triplet states is key efficiency and stability. Current devices rely on high-gap matrices prevent transfer, unfortunately leads overly complex from a fabrication standpoint. Here we introduce molecular design where ultranarrowband emitters are covalently encapsulated by insulating alkylene straps. Organic diodes with simple emissive layers consisting pristine thermally activated delayed fluorescence hosts doped exhibit negligible external quantum drops compared non-doped devices, enabling maximum 21.5%. To explain high in absence matrices, turn transient absorption spectroscopy. It directly observed that sensitizer host can be substantially reduced an emitter, opening door highly efficient ‘matrix-free’ hyperfluorescence.

Language: Английский

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Bright, efficient, and stable pure-green hyperfluorescent organic light-emitting diodes by judicious molecular design

Nature Communications, Journal Year: 2024, Volume and Issue: 15(1)

Published: April 12, 2024

Abstract To fulfill ultra-high-definition display, efficient and bright green organic light-emitting diodes with Commission Internationale de l’Éclairage y-coordinate ≥ 0.7 are required. Although there some preceding reports of highly devices based on pure-green multi-resonance emitters, the efficiency rolloff device stabilities for those still unsatisfactory. Herein, we report rational design two emitters achieving stable CIE x,y s that close to NTSC BT. 2020 standards. In this study, our thermally activated delayed fluorescence OLEDs result in y up 0.74. hyperfluorescent architecture, x further meet x-coordinate requirements, i.e., (0.21) (0.17), while keeping their ~ 0.7. Most importantly, display high maximum external quantum efficiencies over 25% luminance 10 5 cd m −2 suppressed rolloffs (external ~20% at 4 ) long LT 95 600 h.

Language: Английский

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Nitrogen Effects Endowed by Doping Electron-Withdrawing Nitrogen Atoms into Polycyclic Aromatic Hydrocarbon Fluorescence Emitters

Journal of the American Chemical Society, Journal Year: 2024, Volume and Issue: 146(23), P. 15977 - 15985

Published: May 7, 2024

Unveiling innovative mechanisms to design new highly efficient fluorescent materials and, thereby, fabricate high-performance organic light-emitting diodes (OLEDs) is a concerted endeavor in both academic and industrial circles. Polycyclic aromatic hydrocarbons (PAHs) have been widely used as emitters blue OLEDs, but device performances are far from satisfactory. In response, we propose the concept of "nitrogen effects" endowed by doping electron-withdrawing nitrogen atoms into PAH fluorescence emitters. The presence n orbital on imine conducive promoting electron coupling, which leads increased molar absorptivity an accelerated radiative decay rate emitters, thereby facilitating Förster energy transfer (FET) process OLEDs. Additionally, electronically withdrawing enhances host–guest interactions, positively affecting FET horizontal orientation factor emitting layer. To validate concept, cobalt-catalyzed multiple C–H annulation has utilized incorporate alkynes imine-based frameworks, enables various imine-embedded (IE-PAH) cyclization demonstrates notable regioselectivity, offering practical tool precisely introduce peripheral groups at desired positions with bulky alkyl units positioned adjacent atoms, were previously beyond reach through Friedel–Crafts reaction. Blue OLEDs fabricated IE-PAHs exhibit outstanding performance maximum external quantum efficiency (EQEmax) 32.7%. This achievement sets groundbreaking record for conventional PAH-based EQEmax 24.0%.

Language: Английский

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

Small, Journal Year: 2022, Volume and Issue: 18(19)

Published: March 10, 2022

Multi-resonance (MR) thermally activated delayed fluorescent (TADF) emitters are highly attractive due to their superior color purity as well efficient light-harvesting ability from singlets and triplets. However, boron nitrogen-based MR-TADF suffer strong π-π interaction owing rigid flat cores. Herein, a boron-based multi-resonance blue TADF emitter with suppressed intermolecular isomer formation is developed through simple synthetic process by introducing meta-xylene meta-phenyphenyl groups the core. The emitter, mBP-DABNA-Me, shows narrowband emission peak at 467 nm, along full width half maximum of 28 photoluminescence quantum yield 97%. Notably, pure organic light-emitting diode (OLED) realized using showing external efficiency 24.3% stable Commission Internationale de L'Eclairage coordinate (0.124, 0.140). OLED maintained high doping concentration over 20%, attributed between MR emitters.

Language: Английский

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Nitrogen‐Embedded Multi‐Resonance Heteroaromatics with Prolonged Homogeneous Hexatomic Rings

Angewandte Chemie International Edition, Journal Year: 2022, Volume and Issue: 61(14)

Published: Jan. 29, 2022

Nitrogen-containing polycyclic heteroaromatics have exhibited fascinating multi-resonance (MR) characteristics for efficient narrowband emission, but strategies to bathochromic shift their emissions while maintaining the narrow bandwidths remain exclusive. Here, homogeneous hexatomic rings are introduced into nitrogen-embedded MR skeletons prolong π-conjugation length low-energy electronic transitions retaining non-bonding character of remaining parts. The proof-of-the-concept emitters exhibit near unity photoluminescence quantum yields with peaks at 598 nm and 620 small full-width-at-half-maximums 28 31 nm, respectively. Optimal organic light-emitting diodes a high external efficiency 18.2 %, negligible roll-off, ultra-long lifetime degradation an initial luminance 10 000 cd m-2 after 94 hours.

Language: Английский

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