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

---

High‐Efficiency Narrowband Multi‐Resonance Emitter Fusing Indolocarbazole Donors for BT. 2020 Red Electroluminescence and Ultralong Operation Lifetime

Advanced Materials, Journal Year: 2023, Volume and Issue: 35(30)

Published: April 19, 2023

Polycyclic heteroaromatics with multi-resonance (MR) characteristics are attractive materials for narrowband emitters in wide-color-gamut organic light-emitting diodes. However, MR pure-red colors still rare and usually exhibit problematic spectral broadening when redshifting emission. Here, a emitter is reported by fusing indolocarbazole segments into boron/oxygen-embedded skeleton, realizing BT.2020 red electroluminescence the first time together high efficiency an ultralong lifetime. The rigid segment possesses strong electron-donating ability due to its para-positioned nitrogen-π-nitrogen backbone also enlarges π-extension of skeleton suppress structural displacement during radiation, achieving concurrently redshifted narrowed emission spectrum. An maximum at 637 nm full width half-maxima merely 32 (0.097 eV) recorded toluene. corresponding device simultaneously exhibits CIE coordinates (0.708, 0.292) precisely matching point, external quantum 34.4% low roll-off LT95 (time 95% initial luminance) >10 000 h 1000 cd m-2 . These performance superior even those state-of-the-art perovskite quantum-dot-based devices this specific color, paving way toward practical applications.

Language: Английский

---

Enhancing the efficiency and stability of blue thermally activated delayed fluorescence emitters by perdeuteration

Nature Photonics, Journal Year: 2024, Volume and Issue: 18(5), P. 516 - 523

Published: Jan. 29, 2024

Language: Английский

---

Improving the stability and color purity of a BT.2020 blue multiresonance emitter by alleviating hydrogen repulsion

Science Advances, Journal Year: 2023, Volume and Issue: 9(19)

Published: May 12, 2023

Stable deep blue multiresonance emitters with small full width at half maximum (FWHM) are attractive for wide color-gamut organic light-emitting diodes (OLEDs). However, the steric repulsion from spatially close hydrogens would twist skeletons, causing spectral broadening and molecular instability issues. Here, we strategically introduce a mesitylboron locking unit into carbazole-embedded model emitter, alleviating hydrogen repulsions also strengthening para-positioned weak carbon-nitrogen bond in anionic states. An emission peaking 452 nm an FWHM of merely 14 nearly BT.2020 chromaticity coordinates obtained toluene, affording high external quantum efficiency 33.9% sensitizing device. Moreover, impressive LT97 (time to decay 97% initial luminance) 178 hours constant current density 12 mA/cm2 was achieved stable device y coordinate 0.057, 20 times longer than emitter even substantially red-shifted emission.

Language: Английский

---

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

---

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

---

The degradation mechanism of multi-resonance thermally activated delayed fluorescence materials

Nature Communications, Journal Year: 2025, Volume and Issue: 16(1)

Published: Jan. 4, 2025

1,4-Azaborine-based arenes are promising electroluminescent emitters with thermally activated delayed fluorescence (TADF), offering narrow emission spectra and high quantum yields due to a multi-resonance (MR) effect. However, their practical application is constrained by limited operational stability. This study investigates the degradation mechanism of MR-TADF molecules. Electroluminescent devices incorporating these compounds display varied lifetimes, uncorrelated excitonic stability or external efficiency roll-off. Bulk electrolysis reveals significant instability in radical cationic forms compounds, device lifetime linked Faradaic yield oxidation. Comprehensive chemical analyses corroborate that byproducts originated from intramolecular cyclization cation, followed hydrogen atom transfer. The further supported enhanced observed deuterated emitter, attributed secondary kinetic isotope These findings provide insights into stabilizing effects deuteration mechanism-driven strategies for designing improved longevity. often constrains application. Here, authors report direct correlation between oxidative emitter

Language: Английский

---

B−N/B−O Contained Heterocycles as Fusion Locker in Multi‐Resonance Frameworks towards Highly‐efficient and Stable Ultra‐Narrowband Emission

Angewandte Chemie International Edition, Journal Year: 2023, Volume and Issue: 62(45)

Published: Aug. 16, 2023

Fusing condensed aromatics into multi-resonance (MR) frameworks has been an exquisite strategy to modulate the optoelectronic properties, which, however, always sacrifices small full width at half maxima (FWHM). Herein, we strategically embed B-N/B-O contained heterocycles as fusion locker classical MR prototypes, which could enlarge π-extension and alleviate steric repulsion for enhanced planar skeleton suppress high-frequency stretching/ scissoring vibrations ultra-narrowband emissions. Sky-blue emitters with extremely FWHMs of 17-18 nm are thereafter obtained targeted emitters, decreased by (1.4-1.9)-fold compared prototypes. Benefiting from their high photoluminescence quantum yields >90 % fast radiative decay rates >108 s-1 , one those shows a maximum external efficiency 31.9 in sensitized devices, remains 25.8 practical luminance 1,000 cd m-2 FWHM merely 19 nm. Notably long operation half-lifetime 1,278 h is also recorded same device, representing longest lifetimes among sky-blue devices based on emitters.

Language: Английский

---

Marching Toward Long‐Wavelength Narrowband Emissive Multi‐Resonance Delayed Fluorescence Emitters for Organic Light Emitting Diodes

Advanced Optical Materials, Journal Year: 2023, Volume and Issue: 11(22)

Published: Oct. 4, 2023

Abstract Over the past decade, thermally activated delayed fluorescence (TADF) emitters have garnered tremendous impetus because of their ability to harvest 100% excitons for light emission in organic emitting diodes (OLEDs). However, despite superior external quantum efficiencies (> 35%), broad spectra with associated full‐width‐at‐half maximum (FWHM > 70 nm) present a limiting factor that must be solved. Recently, multiple‐resonance TADF (MR‐TADF) materials based on heteroatom doped polyaromatic hydrocarbons gained astonishing attention owing remarkable narrowband < 30 nm). majority reported MR‐TADF falls blue/green region, which inevitably jeopardizes application full‐color OLEDs. Therefore, there is an urgent need develop new molecular designs expanding color‐gamut emitters, i.e., λ em 550 nm without compromising emission. To best current knowledge, no detailed reviews focusing different design strategies producing long‐wavelength been date. this end, review highlighting recent advances constructing presented, and photophysics OLED performance discussed. Finally, status future prospects are

Language: Английский

---

Donor Extension on Spiro‐Acridine Enables Highly Efficient TADF‐OLEDs with Relieved Efficiency Roll‐Off

Advanced Functional Materials, Journal Year: 2023, Volume and Issue: 33(10)

Published: Jan. 17, 2023

Abstract Organic light emitting diodes based on thermally activated delayed fluorescent (TADF) emitters with both high external quantum efficiency (EQE) and low roll‐off are under urgent pursuing. Three TADF fluorene‐spiro‐acridine derivatives as donors developed. Composing of rigid donor acceptor, all exhibit PLQYs 96–99%. Direct conjugation attached acridine offers an enhanced reverse intersystem crossing ( k RISC ) in IA‐TRZ, while the extension via spiro‐junction accelerates radiative decay rate r 2S‐TRZ IT‐TRZ. Remarkably, enable electroluminescent performance EQE 35.6% for 2S‐TRZ, 36.1% IT‐TRZ 32.0% respectively, very luminance up to 100 000 cd m −2 . Surprisingly, that hold larger smaller than IA‐TRZ more relieved roll‐off, indicating significance More importantly, a moderate among these shows lowest which demonstrates comprehensive consideration photophysical processes is important attain excellent devices. It also emphasizes molecular modulation method through side group can induce elaborate control channels finely optimizing emitters. This study provide useful perspective designing practical

Language: Английский

---