Quenching‐Resistant Multiresonance TADF Emitter Realizes 40% External Quantum Efficiency in Narrowband Electroluminescence at High Doping Level

Advanced Materials, Journal Year: 2021, Volume and Issue: 34(3)

Published: Nov. 12, 2021

Multiresonance thermally activated delayed fluorescence (MR-TADF) emitters manifest great potential for organic light-emitting diodes (OLEDs) due to their high exciton-utilization efficiency and narrowband emission. Nonetheless, tendency toward self-quenching caused by strong interchromophore interactions would induce doping sensitivity deteriorate the device performances, effective strategy construct quenching-resistant without sacrifycing color purity is still be developed. By segregating planar MR-TADF skeleton using two bulky carbazolyl units, herein a highly emissive molecule with enhanced quenching resistance reported. The steric effect largely removes formation of detrimental excimers/aggregates, boosts performance corresponding devices maximum external quantum (EQEmax ) up 40.0% full width at half (FWHM) 25 nm, representative only example single OLED that can concurrently achieve narrow bandwidth EL surpassing 40% date. Even ratio 30 wt%, EQEmax retained 33.3% nearly unchanged emission spectrum. This work provides viable approach realize doping-insensitive extreme high-end displays.

Language: Английский

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Narrowband Emissive Thermally Activated Delayed Fluorescence Materials

Advanced Optical Materials, Journal Year: 2022, Volume and Issue: 10(22)

Published: Sept. 23, 2022

Abstract Organic thermally activated delayed fluorescence (TADF) materials have attracted significant research interest in the field of organic electronics because their inherent advantage 100% exciton utilization capability light‐emitting diodes (OLEDs) without use noble metals. However, despite high internal electroluminescence quantum efficiencies approaching unity, broad emission spectra with sizable full width at half maxima (FWHM; 60–100 nm) present a critical issue that must be solved for application ultrahigh‐definition OLED displays. Recently, new paradigm TADF featuring multiple resonance (MR) effect based on heteroatom‐doped polycyclic aromatic frameworks, referred to as MR‐TADF materials, has emerged and garnered considerable owing remarkable features efficient narrowband emissions extremely small FWHMs (≤30 nm). Currently, occupy prominent position cutting‐edge from both chemical physical perspectives. This review article focuses recent progress emissive systems perspective molecular design, photophysical properties, performance OLEDs. The current status future prospects this advanced material technology are discussed comprehensively.

Language: Английский

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Achieving Ultimate Narrowband and Ultrapure Blue Organic Light‐Emitting Diodes Based on Polycyclo‐Heteraborin Multi‐Resonance Delayed‐Fluorescence Emitters

Advanced Materials, Journal Year: 2021, Volume and Issue: 34(9)

Published: Dec. 8, 2021

To achieve an ultimate wide color gamut for ultrahigh-definition displays, there is great demand the development of organic light-emitting diodes (OLEDs) enabling monochromatic, ultrapure blue electroluminescence (EL). Herein, high-efficiency and OLEDs based on polycyclo-heteraborin multi-resonance thermally activated delayed fluorescence (MR-TADF) materials, BOBO-Z, BOBS-Z, BSBS-Z, are reported. The key to design present luminophores exquisite combination interplay multiple boron, nitrogen, oxygen, sulfur heteroatoms embedded in a fused polycyclic π-system. Comprehensive photophysical computational investigations this family MR-TADF materials reveal that systematic implementation chalcogen (oxygen sulfur) atoms can finely modulate emission while maintaining narrow bandwidth, as well spin-flipping rates between excited singlet triplet states. Consequently, BSBS-Z demonstrate narrowband EL emission, with peaks at 445-463 nm full width half maxima 18-23 nm, leading Commission Internationale de l'Éclairage-y coordinates range 0.04-0.08. Particularly, incorporating sulfur-doped BOBS-Z notably high maximum external quantum efficiencies 26.9% 26.8%, respectively, small efficiency roll-offs achieved concurrently.

Language: Английский

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Sterically Wrapped Multiple Resonance Fluorophors for Suppression of Concentration Quenching and Spectrum Broadening

Angewandte Chemie International Edition, Journal Year: 2021, Volume and Issue: 61(2)

Published: Oct. 12, 2021

Multiple resonance (MR) emitters are promising for highly efficient organic light-emitting diodes (OLEDs) with narrowband emission; however, they still face intractable challenges concentration-caused emission quenching, exciton annihilation, and spectral broadening. In this study, sterically wrapped MR dopants a fluorescent core sandwiched by bulk substituents were developed to address the reducing intermolecular interactions. Consequently, high photo-luminance quantum yields of ≥90 % small full width at half maximums (FWHMs) ≤25 nm over wide range dopant concentrations (1-20 wt %) recorded. addition, we demonstrated that emitter can effectively suppress Dexter interaction when doped in thermally activated delayed fluorescence sensitizer, eliminating loss through triplet. Within above concentration range, optimal realizes remarkably maximum external efficiencies 36.3-37.2 %, identical FWHMs 24 nm, alleviated efficiency roll-offs OLEDs.

Language: Английский

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One-Shot Synthesis of Expanded Heterohelicene Exhibiting Narrowband Thermally Activated Delayed Fluorescence

Journal of the American Chemical Society, Journal Year: 2021, Volume and Issue: 144(1), P. 106 - 112

Published: Dec. 23, 2021

An expanded heterohelicene consisting of three BN2-embedded [4]helicene subunits (V-DABNA-Mes) has been synthesized by one-shot triple borylation. The key to success is the excessive use boron tribromide in an autoclave. Based on multiple resonance effect and six nitrogen atoms, V-DABNA-Mes exhibited a narrowband sky-blue thermally activated delayed fluorescence with full width at half-maximum 16 nm. resonating π-extension minimized singlet-triplet energy gap enabled rapid reverse intersystem crossing rate constant 4.4 × 105 s-1. solution-processed organic light-emitting diode device, employed as emitter, emission 480 nm high external quantum efficiency 22.9%.

Language: Английский

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Wide‐Range Color Tuning of Narrowband Emission in Multi‐resonance Organoboron Delayed Fluorescence Materials through Rational Imine/Amine Functionalization

Angewandte Chemie International Edition, Journal Year: 2021, Volume and Issue: 60(43), P. 23142 - 23147

Published: Aug. 18, 2021

Abstract Establishing a simple and versatile design strategy to finely modulate emission colors while retaining high luminescence efficiency color purity remains an appealing yet challenging task for the development of multi‐resonance‐induced thermally activated delayed fluorescence (MR‐TADF) materials. Herein, we demonstrate that strategic introduction electron‐withdrawing imine electron‐donating amine moieties into boron‐embedded 1,3‐bis(carbazol‐9‐yl)benzene skeleton enables systematic hypsochromic bathochromic shifts narrowband emissions, respectively. By this method, effective electroluminescence tuning was accomplished over wide visible range from deep‐blue yellow (461–571 nm), using same MR molecular system, without compromising very narrow spectral features. Deep‐blue organic light‐emitting diodes with maximum external quantum efficiencies as 19.0–29.2 % superb could be produced family color‐tunable MR‐TADF emitters.

Language: Английский

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Extending the π‐Skeleton of Multi‐Resonance TADF Materials towards High‐Efficiency Narrowband Deep‐Blue Emission

Angewandte Chemie International Edition, Journal Year: 2022, Volume and Issue: 61(29)

Published: May 10, 2022

Multi-resonance TADF (MR-TADF) emitters are promising for high-resolution OLEDs, but the concurrent optimization of excited-state dynamics and color purity remains a tough challenge. Herein, three deep-blue MR-TADF compounds (BN1-BN3) featuring gradually enlarged ring-fused structures increased rigidity accessed by lithium-free borylation in high yields from same precursor, with all possessing CIEy coordinates below 0.08. Structure-property investigations demonstrate strategic improvement oscillator strength (fosc ) acceleration reverse intersystem crossing (RISC) process extending π-skeleton, where BN3 realizes maximum external quantum efficiency (EQE) 37.6 % reduced roll-off, thus showing best reported OLEDs. The internal regulation these validate general effectiveness to achieve advanced narrowband higher-order boron/nitrogen-based MR motifs.

Language: Английский

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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 Asymmetric Multiple Resonance Thermally Activated Delayed Fluorescence Emitter with EQE of 32.8 % and Extremely Low Efficiency Roll‐Off

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

Published: Feb. 1, 2022

Multiple resonance thermally activated delayed fluorescence (MR-TADF) emitters show great potentials for high color purity organic light-emitting diodes (OLEDs). However, the simultaneous realization of photoluminescence quantum yield (PLQY) and reverse intersystem crossing rate (kRISC ) is still a formidable challenge. Herein, novel asymmetric MR-TADF emitter (2Cz-PTZ-BN) designed that fully inherits PLQY large kRISC values properly selected parent molecules. The resonating extended π-skeleton with peripheral protection can achieve 96 % fast above 1.0×105 s-1 , boost performance corresponding pure green devices an outstanding external efficiency (EQE) up to 32.8 without utilizing any sensitizing hosts. Remarkably, device sufficiently maintains EQE exceeding 23 at luminance 1000 cd m-2 representing highest value reported materials same luminescence.

Language: Английский

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Space‐Confined Donor‐Acceptor Strategy Enables Fast Spin‐Flip of Multiple Resonance Emitters for Suppressing Efficiency Roll‐Off

Angewandte Chemie International Edition, Journal Year: 2022, Volume and Issue: 61(40)

Published: Aug. 18, 2022

Multi-resonance boron-nitrogen-containing thermally activated delayed fluorescence (MR-TADF) emitters have experienced great success in assembling narrowband organic light-emitting diodes (OLEDs). However, the slow reverse intersystem crossing rate (kRISC ) of MR-emitters (103 -105 s-1 that will lead to severe device efficiency roll-off has received extensive attention and remains a challenging issue. Herein, we put forward "space-confined donor-acceptor (SCDA)" strategy accelerate RISC process. The introduction SCDA units onto MR-skeleton induces intermediate triplet states, which leads multichannel process thus increases kRISC . As illustrated examples, efficient been developed with sub-microsecond lifetime high 2.13×106 , enables assemble high-performance OLEDs maximum external quantum (EQEmax as 32.5 % an alleviated (EQE1000 : 22.9 %).

Language: Английский

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