Ultrafast Triplet–Singlet Exciton Interconversion in Narrowband Blue Organoboron Emitters Doped with Heavy Chalcogens

Angewandte Chemie International Edition, Journal Year: 2022, Volume and Issue: 61(31)

Published: May 27, 2022

Narrowband emissive organoboron emitters featuring the multi-resonance (MR) effect have now become a critical material component for constructing high-performance organic light-emitting diodes (OLEDs) with pure emission colors. These MR are capable of exhibiting high-efficiency narrowband thermally activated delayed fluorescence (TADF) by allowing triplet-to-singlet reverse intersystem crossing (RISC). However, RISC involving spin-flip exciton upconversion is generally rate-limiting step in overall TADF; hence, deeper understanding and precise control dynamics ongoing crucial challenges. Here, we introduce first emitter (CzBSe) doped selenium atom, demonstrating record-high rate exceeding 108 s-1 , which even higher than its radiation rate. Furthermore, process CzBSe can be accelerated factors ≈20000 ≈800, compared to those oxygen- sulfur-doped homologs (CzBO CzBS), respectively. Unlike CzBO CzBS, photophysical no longer RISC, but process; this behavior completely different from conventional time-delaying TADF limited slow RISC. Benefitting ultrafast spin conversion ability, OLEDs incorporating achieved maximum external electroluminescence quantum efficiency as high 23.9 %, accompanied MR-induced blue significantly alleviated roll-off features.

Language: Английский

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Highly Efficient Purely Organic Phosphorescence Light‐Emitting Diodes Employing a Donor–Acceptor Skeleton with a Phenoxaselenine Donor

Advanced Science, Journal Year: 2023, Volume and Issue: 10(12)

Published: Feb. 20, 2023

Purely organic room-temperature phosphorescence (RTP) materials generally exhibit low quantum yield (ϕP ) and long lifetime (τP due to the theoretically spin-forbidden triplet state. Herein, by introducing a donor-acceptor (D-A) skeleton with phenoxaselenine donor, three nonaromatic amine donor containing compounds high ϕP short τP in amorphous films are developed. Besides enhanced spin-orbit coupling (SOC) heavy-atom effect of selenium, D-A which facilitates orbital angular momentum change can further boost SOC, severe nonradiative energy dissipation is also suppressed rigid molecular structure. Consequently, record-high external efficiency 19.5% achieved for RTP light-emitting diode (OLED) based on 2-(phenoxaselenin-3-yl)-4,6-diphenyl-1,3,5-triazine (PXSeDRZ). Moreover, voltage-dependent color-tunable emission single-molecule white realized. These results shed light broad prospects purely as highly efficient OLED emitters especially potential charming lighting applications.

Language: Английский

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Modulating the Photophysical Properties of Twisted Donor–Acceptor–Donor π-Conjugated Molecules: Effect of Heteroatoms, Molecular Conformation, and Molecular Topology

Accounts of Chemical Research, Journal Year: 2024, Volume and Issue: 57(15), P. 2219 - 2232

Published: July 24, 2024

ConspectusModulating the photophysical properties of organic emitters through molecular design is a fundamental endeavor in materials science. A critical aspect this process control excited-state energy, which essential for development triplet exciton-harvesting emitters, such as those with thermally activated delayed fluorescence and room-temperature phosphorescence. These are pivotal developing highly efficient light-emitting diodes bioimaging probes. particularly promising class these consists twisted donor-acceptor π-conjugated scaffolds. structures facilitate spatial separation frontier orbitals, crucial achieving narrow singlet-triplet energy gap. This gap necessary to overcome endothermic reverse intersystem crossing process, enhancing efficiency fluorescence. To precisely modulate emitting materials, it understand electronic new scaffolds, especially influenced by heteroatoms, well their conformations topologies. understanding not only improves but also expands potential applications advance technologies.In 2014, Takeda group made significant breakthrough discovering novel method synthesizing U-shaped diazaacenes (dibenzo[

Language: Английский

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Highly Efficient Sky‐Blue π‐Stacked Thermally Activated Delayed Fluorescence Emitter with Multi‐Stimulus Response Properties

Angewandte Chemie International Edition, Journal Year: 2022, Volume and Issue: 61(34)

Published: June 11, 2022

Organic materials with multi-stimulus response (MSR) properties have demonstrated many potential and practical applications. Herein, a π-stacked thermally activated delayed fluorescence (TADF) material properties, named SDMAC, was designed synthesized using distorted 9,9-dimethyl-10-phenyl-9,10-dihydroacridine as donor. SDMAC possesses rigid configuration intramolecular through-space interactions exhibits aggregation-induced emission enhancement (AIEE), solvatochromic, piezochromic, circularly polarized luminescence (CPL) under different external stimuli. The molecular structure efficient TADF of can be used in displays lighting. Using an emitter, the maximum quantum efficiency (EQE) fabricated organic light-emitting diodes (OLEDs) is high 28.4 %, which make them most CP-TADF OLEDs based on charge transfer strategy. CP (CP-OLEDs) exhibit electroluminescence (CPEL) signals.

Language: Английский

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Enhancing multi-resonance thermally activated delayed fluorescence emission via through-space heavy-atom effect

Chem, Journal Year: 2024, Volume and Issue: unknown

Published: Nov. 1, 2024

Language: Английский

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Folding-Induced Spin–Orbit Coupling Enhancement for Efficient Pure Organic Room-Temperature Phosphorescence

The Journal of Physical Chemistry Letters, Journal Year: 2022, Volume and Issue: 13(6), P. 1563 - 1570

Published: Feb. 9, 2022

For the direct luminescence of triplet excitons, different mechanisms have been proposed for realizing pure organic room-temperature phosphorescence (RTP). To further verify mechanism folding-induced spin-orbit coupling (SOC) enhancement, two analogues thianthrene (TA) were introduced by gradually replacing sulfur atom with an oxygen a systematical comparison, corresponding to phenoxathiine (PX) and dioxins (DX) molecules increasing folding dihedral angles (or decreasing degrees folding). Photophysical measurements show obviously enhanced RTP efficiency from DX PX TA, which is consistent their greatly SOC decrease in angle. The angle-dependent calculations each molecule reveal that this dominated contrast negligible heavy-atom effect sulfur. This work validates rationality enhancement mechanism, provides innovative molecular design strategy developing efficient materials using structures.

Language: Английский

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Ultrafast Triplet–Singlet Exciton Interconversion in Narrowband Blue Organoboron Emitters Doped with Heavy Chalcogens

Angewandte Chemie, Journal Year: 2022, Volume and Issue: 134(31)

Published: May 27, 2022

Abstract Narrowband emissive organoboron emitters featuring the multi‐resonance (MR) effect have now become a critical material component for constructing high‐performance organic light‐emitting diodes (OLEDs) with pure emission colors. These MR are capable of exhibiting high‐efficiency narrowband thermally activated delayed fluorescence (TADF) by allowing triplet‐to‐singlet reverse intersystem crossing (RISC). However, RISC involving spin‐flip exciton upconversion is generally rate‐limiting step in overall TADF; hence, deeper understanding and precise control dynamics ongoing crucial challenges. Here, we introduce first emitter ( CzBSe ) doped selenium atom, demonstrating record‐high rate exceeding 10 8 s −1 , which even higher than its radiation rate. Furthermore, process can be accelerated factors ≈20000 ≈800, compared to those oxygen‐ sulfur‐doped homologs CzBO CzBS ), respectively. Unlike photophysical no longer RISC, but process; this behavior completely different from conventional time‐delaying TADF limited slow RISC. Benefitting ultrafast spin conversion ability, OLEDs incorporating achieved maximum external electroluminescence quantum efficiency as high 23.9 %, accompanied MR‐induced blue significantly alleviated roll‐off features.

Language: Английский

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Efficient Purely Organic Room-Temperature Phosphorescence from Selenium-Containing Conjugated Polymers for Signal-Amplified Oxygen Detection

Macromolecules, Journal Year: 2023, Volume and Issue: 56(8), P. 2972 - 2979

Published: April 4, 2023

Purely organic room-temperature phosphorescent (RTP) polymers with good processability and flexibility over small molecular crystals are highly attractive. Although many non-conjugated (non-CPs) efficient RTP emission have been reported, the development of metal-free CPs remains a formidable challenge. Herein, clear in both doped neat films readily prepared by introducing selenium-containing phenoselenazine unit into conjugated backbones. The resulting can achieve phosphorescence lifetimes ranging from microseconds to milliseconds quantum yields up 17.2% film states, representing highest value for CPs. Moreover, these polymer be used ratiometric oxygen detection due their sensitive oxygen. Remarkably, first time, demonstrate significant signal amplification Stern–Volmer quenching constant (KSV) 5.54 × 10–3 ppm–1, which is 250 times higher than that molecule counterpart.

Language: Английский

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Modulation of Delayed Fluorescence Guided by Conformational Effect-Mediated Thermally Enhanced Phosphorescence in Phenothiazines–Quinoline–Cl Conjugates

The Journal of Physical Chemistry B, Journal Year: 2023, Volume and Issue: 127(45), P. 9833 - 9840

Published: Nov. 1, 2023

Triplet energy harvesting via thermally activated delayed fluorescence (TADF) from pure organic systems has attracted great attention in light-emitting diodes, sensing, and photocatalysis. However, the realization of enhanced phosphorescence (TEP)-guided efficient TADF with a high rate reverse intersystem crossing (kRISC) still needs to be discovered. Herein, we report two phenothiazine-quinoline conjugates (P2QC, P2QMC) comprising phenothiazine donors covalently attached chlorine-substituted quinolinyl acceptor. Spectroscopic analysis conjunction quantum chemistry calculations reveals that TEP P2QC originated due slow internal conversion higher-lying triplet lowest (T2' → T1') quasi-axial (QA) conformer (kRISC = 1.44 × 108 s-1) quasi-equatorial (QE) caused by low singlet-triplet gap (ΔES1-T1 0.11 eV) transfer QA QE owing degenerate ground state conformers. In contrast, 0.74 dual under ambient conditions are observed P2QMC. This study provides sustainable guideline for developing emitters conformation effects mechanisms.

Language: Английский

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Thermally Activated Delayed Fluorescence and Room-Temperature Phosphorescence in Asymmetric Phenoxazine-Quinoline (D2–A) Conjugates and Dual Electroluminescence

The Journal of Physical Chemistry C, Journal Year: 2022, Volume and Issue: 126(12), P. 5649 - 5657

Published: March 17, 2022

Triplet energy harvesting via either thermally activated delayed fluorescence (TADF) or room-temperature phosphorescence (RTP) from pure organic systems has attracted great attention in the field of light-emitting diodes, sensing, and bioimaging. However, realization dual electroluminescence TADF RTP single molecules remains elusive. Herein, we report two phenoxazine-quinoline conjugates (DPQ DPQM) which phenoxazine donors are covalently attached to 6,8-positions 2,4-diphenylquinoline and/or 7-methyl-2,4-diphenylquinoline acceptors. Experimental quantum chemistry calculations combining reference compounds (o-PQP, p-PQP, Phox, QPP) reveal that both show (with different rate constants reverse intersystem crossing, krISC = 0.43–1.30 × 106 s–1) crossing charge transfer triplet (3CT) singlet (1CT) states mediated by vibronic coupling among 1CT, local (3LE), 3CT due close gaps. Further, with yields (ϕP) ca. 21–24% features was also observed radiative decay 3LE states. Phosphorescence measurements DPQM at low temperatures (T 77, 10 K) ensure a distinct zero-field splitting T1(CT) into substates. Both showed external efficiencies 11–12% efficient channels.

Language: Английский

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