High External Quantum Efficiency Research Articles

Room-temperature efficient and tunable interlayer exciton emissions in WS2/WSe2 heterobilayers at high generation rates.

Transition metal dichalcogenide (TMDC) heterobilayers (HBs) have been intensively investigated lately because they offer novel platforms for the exploration of interlayer excitons (IXs). However, the potentials of IXs in TMDC HBs have not been fully studied as efficient and tunable emitters for both photoluminescence (PL) and electroluminescence (EL) at room temperature (RT). Also, the efficiencies of the PL and EL of IXs have not been carefully quantified. In this work, we demonstrate that IX in WS2/WSe2 HBs could serve as promising emitters at high generation rates due to its immunity to efficiency roll-off. Furthermore, by applying gate voltages to balance the electron and hole concentrations and to reinforce the built-in electric fields, high PL quantum yield (QY) and EL external quantum efficiency (EQE) of ∼0.48% and ∼0.11% were achieved at RT, respectively, with generation rates exceeding 1021 cm-2·s-1, which confirms the capabilities of IXs as efficient NIR light emitters by surpassing most of the intralayer emissions from TMDCs.

Dual‐Core Engineering for Efficient Deep‐Blue Multiple Resonance Thermally Activated Delayed Fluorescent Materials

AbstractDeveloping narrowband blue multiple resonance (MR) organic emitters with Commission Internationale de L'Eclairage (CIE) y coordinates <0.1 is essential for advanced display technologies. This study proposes a deep‐blue thermally activated delayed fluorescence (TADF) emitter, named 2BNO, which integrates two independent MR cores. Unlike many TADF materials with single‐bonded dual emitting cores, 2BNO utilizes a steric hindrance‐assisted fluorene bridge to achieve an orthorhombic molecular structure. The dual‐core MR‐TADF emitter shows enhanced light absorption and a high photoluminescence quantum yield. Notably, the emission of 2BNO is not significantly redshifted compared to single‐core compounds and maintains a narrow full width at half‐maximum (FWHM) of 24 nm with CIE coordinates of (0.147, 0.041) in 2Me‐THF solution, nearing the BT.2020 blue standard. Organic light‐emitting diodes (OLEDs) incorporating 2BNO as the emitter exhibit deep‐blue emission at 460 nm with a narrow FWHM of 29 nm and CIE coordinates of (0.14, 0.09). The dual emitting core design significantly improves device efficiency, achieving a high external quantum efficiency (EQE) of 19.8%. The dual‐core molecular design strategy in this work is demonstrated to be effective in promoting the efficiency of the TADF emitters while preserving deep‐blue color purity.

Multiple Enol-Keto Isomerization and Excited-State Unidirectional Intramolecular Proton Transfer Generate Intense, Narrowband Red OLEDs.

A novel series of excited-state intramolecular proton transfer (ESIPT) emitters, namely, DPNA, DPNA-F, and DPNA-tBu, endowed with dual intramolecular hydrogen bonds, were designed and synthesized. In the condensed phase, DPNAs exhibit unmatched absorption and emission spectral features, where the minor 0-0 absorption peak becomes a major one in the emission. Detailed spectroscopic and dynamic approaches conclude fast ground-state equilibrium among enol-enol (EE), enol-keto (EK), and keto-keto (KK) isomers. The equilibrium ratio can be fine-tuned by varying the substitutions in DPNAs. Independent of isomers and excitation wavelength, ultrafast ESIPT takes place for all DPNAs, giving solely KK tautomer emission maximized at >650 nm. The spectral temporal evolution of ESIPT was resolved by a state-of-the-art technique, namely, the transient grating photoluminescence (TGPL), where the rate of EK* → KK* is measured to be (157 fs)-1 for DPNA-tBu, while a stepwise process is resolved for EE* → EK* → KK*, with a rate of EE* → EK* of (72 fs)-1. For all DPNAs, the KK tautomer emission shows a narrowband emission with high photoluminescence quantum yields (PLQY, ∼62% for DPNA in toluene) in the red, offering advantages to fabricate deep-red organic light-emitting diodes (OLED). The resulting OLEDs give high external quantum efficiency with a spectral full width at half-maximum (FWHM) as narrow as ∼40 nm centered at 666-670 nm for DPNAs, fully satisfying the BT. 2020 standard. The unique ESIPT properties and highly intense tautomer emission with a small fwhm thus establish a benchmark for reaching red narrowband organic electroluminescence.

Efficient and Stable Red Perovskite Light-Emitting Diodes via Thermodynamic Crystallization Control.

Efficient and stable red perovskite light-emitting diodes (PeLEDs) demonstrate promising potential in high-definition displays and biomedical applications. Although significant progress has been made in device performance, meeting commercial demands remains a challenge in the aspects of long-term stability and high external quantum efficiency (EQE). Here, an in situ crystallization regulation strategy is developed for optimizing red perovskite films through ingenious vapor design. Mixed vapor containing dimethyl sulfoxide and carbon disulfide (CS2) is incorporated to conventional annealing, which contributes to thermodynamics dominated perovskite crystallization for well-aligned cascade phase arrangement. Additionally, the perovskite surface defect density is minimized by the CS2 molecule adsorption. Consequently, the target perovskite films exhibit smooth exciton energy transfer, reduced defect density, and blocked ion migration pathways. Leveraging these advantages, spectrally stable red PeLEDs are obtained featuring emission at 668, 656, and 648nm, which yield record peak EQEs of 30.08%, 32.14%, and 29.04%, along with prolonged half-lifetimes of 47.7, 60.0, and 43.7h at the initial luminances of 140, 250, and 270cd m-2, respectively. This work provides a universal strategy for optimizing perovskite crystallization and represents a significant stride toward the commercialization of red PeLEDs.

Thermally Activated Delayed Fluorescence and Beyond. Photophysics and Material Design Strategies.

This review focuses on thermally activated delayed fluorescence (TADF). Photophysical properties of Cu(I) complexes and unique organic molecules are addressed. Investigations, based on temperature‐dependent emission studies, micro‐ to femto‐second time‐resolved spectroscopy investigations, quantum mechanical considerations, state‐of‐art calculations, and organic light‐emitting diodes (OLED) device studies, address exciton harvesting mechanisms and photophysical impact of the energy gap ΔE(S1–T1) and spin‐orbit coupling (SOC). We disclose relationship between (i) ΔE(S1–T1) and transition rate k(S1–S0); (ii) SOC, phosphorescence, and intersystem crossing (ISC); (iii) internal/external rigidity, luminescence quantum yield, excitation self‐trapping, and concentration quenching; (iv) environment polarity and state energy tuning, as well as (v) SOC and combined ambient‐temperature TADF/phosphorescence, zero‐field splitting, and spin‐lattice relaxation (at T = 1.2 K). These studies guide us to milestone Cu(I) complexes. Moreover, we demonstrate that fast ISC in organic molecules requires state mixing with an additional, energetically close triplet state. Thus, a guide structure for unique organic TADF molecules with ultra‐fast ISC and reverse‐ISC rates (>109 s−1) combined with ΔE(S1–T1)<10 cm−1 (<1 meV) is presented allowing for ultra‐fast singlet‐triplet equilibrated fluorescence with sub‐microsecond decay. First OLEDs fabricated show high external quantum efficiency of ≈19%. Based on this breakthrough material class, a new exciton harvesting mechanism, the direct singlet harvesting (DSH), is presented.

High‐Efficiency Deep Red Fluorescent Material with Aggregation Induced Emission and the Application in Organic Light‐Emitting Diodes

AbstractThe development of highly efficient deep red materials with emission wavelength beyond 650 nm remains a big challenge due to the constraints imposed by the energy gap rule. In this work, a donor‐acceptor‐donor type emitter, 4,7‐bis (10‐(4‐(tert‐butyl) phenyl)‐10H‐phenothiazin‐3‐yl) benzo[c][1,2,5] thiadiazole (TBPPTZ) is designed and synthesized. Resulting from the slight twist angle between the donor and acceptor units, TBPPTZ exhibits nearly planar conformation and an extended conjugated structure. TBPPTZ shows a deep red emission peak at 687 nm and aggregation induced emission property with a high photoluminescence quantum yield of 45 % in neat thin film. The optimized organic light‐emitting diode (OLEDs) utilizing TBPPTZ as the non‐doped emissive layer obtains a high external quantum efficiency (EQE) up to 2.51 % with an electroluminescence (EL) peak at 676 nm, aligning with the Commission Internationale de L'Eclairage (CIE) coordinates (0.68, 0.31), which shows a small EQE roll‐off of only 5.6 % at 100 cd m−2. Additionally, the doped OLED achieves an EQE up to 5.09 %, with an EL peak at 656 nm and CIE coordinates of (0.65, 0.34). The findings of this research not only contribute to achieve highly efficient deep red OLEDs but also offer a novel and effective deep red molecular strategy to realize high‐quality OLEDs.

Ultrathin, High-Aspect-Ratio Bismuth Sulfohalide Nanowire Bundles for Solution-Processed Flexible Photodetectors.

In this study, a novel synthesis of ultrathin, highly uniform colloidal bismuth sulfohalide (BiSX where X = Cl, Br, I) nanowires (NWs) and NW bundles (NBs) for room-temperature and solution-processed flexible photodetectors are presented. High-aspect-ratio bismuth sulfobromide (BiSBr) NWs are synthesized via a heat-up method using bismuth bromide and elemental S as precursors and 1-dodecanethiol as a solvent. Bundling of the BiSBr NWs occurs upon the addition of 1-octadecene as a co-solvent. The morphologies of the BiSBr NBs are easily tailored from sheaf-like structures to spherulite nanostructures by changing the solvent ratio. The optical bandgaps are modulated from 1.91 (BiSCl) and 1.88eV (BiSBr) to 1.53eV (BiSI) by changing the halide compositions. The optical bandgap of the ultrathin BiSBr NWs and NBs exhibits blueshift, whose origin is investigated through density functional theory-based first-principles calculations. Visible-light photodetectors are fabricated using BiSBr NWs and NBs via solution-based deposition followed by solid-state ligand exchanges. High photo-responsivities and external quantum efficiencies (EQE) are obtained for BiSBr NW and NB films even under strain, which offer a unique opportunity for the application of the novel BiSX NWs and NBs in flexible and environmentally friendly optoelectronic devices.

Enhanced UV photodetector performance using sputtered Mg-doped ZnO thin film

In this article, we demonstrate UV photodetector synthesized using Mg-doped ZnO thin film (TF) (10 % Mg) grown on a p-Si substrate using the radio frequency (RF) magnetron sputtering system. The fabricated MgZnO TF was annealed at 500 °C in air resulting in notable changes in morphology, optical band gap and crystallinity that significantly improved the UV light sensitivity. The annealed device (MgZnO TF/p-Si) exhibited a remarkable 155-fold increase in photocurrent density compared to the as-deposited device at + 2 V bias. Also, at the same bias the annealed device (500 °C) exhibited high photosensitivity (up to 1262 times), responsivity (20.32 A/W), specific detectivity (1.82 × 1013 Jones) and external quantum efficiency (EQE) (7745 %) in comparison to the as-deposited device. Additionally, the 500 °C device achieved a low noise equivalent power (NEP) of 0.07 × 10−12 W which is about 262 times lower than that of the as-deposited device (18.4 × 10−12 W). Furthermore, on UV illumination (λ = 325 nm) the MgZnO TF/p-Si (500 °C) detector showed fast device response with rise time/fall time values of 0.26 s/0.25 s respectively at + 2 V applied bias.

Spin-Flip-Restricted Multiple-Resonance Emitters for Extended Device Lifetime in Indolocarbazole-Based Blue Organic Light-Emitting Diodes.

In this study, a multiple-resonance (MR) core structure is developed with a spin-flip-restricted emission mechanism based on a fused indolo[3,2,1-jk]carbazole (ICz) framework as emitters to improve the lifetime of blue organic light-emitting diodes. The molecular skeleton modulation approach applied to the conjugated π-system effectively stabilizes the triplet energy of the fused ICz emitters and narrows the full-width-at-half maximum (<20nm). In addition, the emitters exhibit higher exciton stability than conventional boron-based MR emitters. The fused ICz-based blue fluorescent device exhibits a high external quantum efficiency of 7.2%, a blue index of 68.6cd A-1 at a Commission internationale de l'éclairage y coordinate (CIEy) of 0.075, and a device lifetime 1.8 times longer than that of a boron-based emitter. In addition, a phosphor-sensitized fluorescent device based on the ICz emitter exhibited an improved external quantum efficiency of 20.6% with a CIEy coordinate of 0.076.

Manganese doping in zinc based hybrid metal halides to realize highly stable efficient green emission and flexible radiation detection

Extensive studies have been conducted on hybrid metal halides due to their application in radiation detection, solid-state lighting, and solar cells. Here, we present an environmentally friendly zero-dimensional halide, (C9H15N3)ZnBr4, which crystallizes in the P21/c space group. This compound is highly thermally stable, and doping Mn2+ results in a bright green light emission, with an impressive internal quantum efficiency of 52.9 % and an external quantum efficiency of 45.9 % for (C9H15N3)Mn0.3Zn0.7Br4. Combining spectroscopic analysis with first-principles density functional theory (DFT), it is concluded that the high external quantum efficiency arises from efficient energy transfer from the organic component to the [MnBr4]2-. Notably, the (C9H15N3)Mn0.3Zn0.7Br4 luminescence intensity maintains 50 % of its room temperature level even at 400 K. Moreover, these doped powders display exceptional scintillation performance, higher than Bi4Ge3O12. Finally, the radioluminescence intensity of (C9H15N3)Mn0.3Zn0.7Br4@polydimethylsiloxane flexible films is about three times that of Bi4Ge3O12. These features position Mn:(C9H15N3)ZnBr4 as an ideal material for X-ray detection and an efficient green photoluminescent material.

Benzimidazole based electron-transport hosts for efficient pure blue narrowband OLED device

Two electron-transport host materials are synthesized by linking anthracene with benzimidazole derivatives through a unit of methyl substituted phenyl. The methyl substitution generates a large dihedral angle between the benzimidazole plane and bridging phenyl, keeping the excited state distribution and energy levels of T1 and S1 unchanged. The electron-only devices reveal that the two hosts have obviously enhanced electron transport ability than that of Ph-AN-MBP without benzimidazole. As a result, the devices with Ph-AN-BIZ and N1-AN-BIZ as hosts and a blue multiple resonance material of tBuCz-DABNA as emitter exhibit high external quantum efficiency of 10.1 % and 9.1 %, respectively, and low turn-on voltage of 2.7 V, which is better than those of Ph-AN-MBP based device (7.9 %, 3.4 V). And their electroluminescence spectra have a very small full-width at half-maximum of 16.2 nm and pure blue color with CIE coordinates of (0.12, 0.11).

Blue thermally activated delayed fluorescence excimers with high external quantum efficiency and accelerated reverse intersystem crossing

This study reports for the first time the development of an efficient blue excimer with thermally activated delayed fluorescence (TADF) properties using a multi-resonance TADF-type fused indolo[3,2,1-jk]carbazole-derived compound with a planar structure for facile excimer formation. The blue excimer was efficiently generated by doping the indolo[3,2,1-jk]carbazole-derived emitter at a high doping concentration. The photophysical analysis demonstrated that the photoluminescence quantum yield (PLQY), rate coefficients of reverse intersystem crossing (RISC), and horizontal emitting dipole orientation values were improved by excimer formation in the solid film compared with the monomer-dominant solid film by suppressing the concentration-quenching effect. Specifically, the delayed PLQY increased because of the efficient RISC process at high doping concentrations. Consequently, an enhanced maximum external quantum efficiency of 26.3% was obtained in the excimer device (15 wt%) compared with 15.2% in the monomer prevalent device (1 wt%). Moreover, the excimer device showed a peak wavelength of 473 nm and color coordinate of (0.13, 0.19). This demonstration is the first of excimer TADF organic light-emitting diodes with a blue emission and a high external quantum efficiency of 26.3%.

Isomer engineering of triptycene-fused multi-resonance TADF emitters: Implications for controlling blue electroluminescence performance

Concurrently achieving high efficiency, narrowband emission, and low efficiency roll-off remains a challenging task for realizing stable blue organic light-emitting diodes (OLEDs) with high color purity. To tackle this issue, herein, two isomeric pairs of B,N-doped multi-resonance thermally activated delayed fluorescence (MR-TADF) emitters, namely, 2,3-Tp-BuDABNA-R and 3,4-Tp-BuDABNA-R (R=H, 3,5-Xyl), featuring triptycene (Tp) moieties fused into the 2,3- and 3,4-positions of the B,N core, respectively, are presented. Both isomeric forms exhibit blue emissions with near-unity photoluminescence (PL) quantum yields in their doped host films. Notably, the 3,4-Tp-fused emitter shows 6-fold faster reverse intersystem crossing (RISC) compared to the 2,3-Tp-fused emitter, albeit with PL spectral broadening. Along with a smaller activation energy of RISC, the stronger spin–orbit coupling between the singlet (S1) and triplet (T2) excited states of the 3,4-Tp-fused emitter is suggested to facilitate the RISC process. Furthermore, a high-frequency vibration in the Tp-fused benzene ring, accompanied by a large reorganization energy, is found to mainly contribute to the spectral broadening of the 3,4-Tp-fused emitter. Blue TADF-OLEDs based on each isomeric emitter similarly achieve a high maximum external quantum efficiency of ∼ 26%. Remarkably, the devices with the 3,4-isomer exhibit significantly reduced efficiency roll-offs compared to the 2,3-isomer, demonstrating that isomer engineering of MR emitters can have a distinct impact on controlling device performance.

Efficient Deep-Blue Light-Emitting Diodes Through Decoupling of Colloidal Perovskite Quantum Dots.

Metal halide perovskite light-emitting diodes (PeLEDs) have exceptional color purity but designs that emit deep-blue color with high efficiency have not been fully achieved and become more difficult in the thin film of confined perovskite colloidal quantum dots (PeQDs) due to particle interaction. Here it is demonstrated that electronic coupling and energy transfer in PeQDs induce redshift in the emission by PeQD film, and consequently hinder deep-blue emission. To achieve deep-blue emission by avoiding electronic coupling and energy transfer, a QD-in-organic solid solution is introduced to physically separate the QDs in the film. This physical separation of QDs reduces the interaction between them yielding a blueshift of ≈7nm in the emission spectrum. Moreover, using a hole-transporting organic molecule with a deep-lying highest occupied molecular orbital (≈6.0eV) as the organic matrix, the formation of exciplex emission is suppressed. As a result, an unprecedently high maximum external quantum efficiency of 6.2% at 462nm from QD-in-organic solid solution film in PeLEDs is achieved, which satisfies the deep-blue color coordinates of CIEy <0.06. This work suggests an important material strategy to deepen blue emission without reducing the particle size to <≈4nm.

Reverse Intersystem Crossing Boosting Sensitizer for Ultra-High Efficiency Blue Organic Light-Emitting Diode.

In designing thermally activated delayed fluorescence (TADF) emitters, a high reverse intersystem crossing (RISC) rate with a high photoluminescence quantum yield is essential. Herein, two blue TADF molecules, 2',5'-di(9H-carbazol-9-yl)-3',6'-bis(3,6-ditert-butyl-9H-carbazol-9-yl)-[1,1':4',1″-terphenyl]-4,4″-dicarbonitrile (CzTCzPhBN) and 2',5'-bis(3,6-ditert-butyl-9H-carbazol-9-yl)-3',6'-bis(3,6-diphenyl-9H-carbazol-9-yl)-[1,1':4',1″-terphenyl]-4,4″-dicarbonitrile (PhCzTCzPhBN) with a high RISC rate, were developed through donor engineering. CzTCzPhBN and PhCzTCzPhBN showed a high RISC rate of 4.00 × 105 and 16.62 × 105 s-1, respectively, with a high photoluminescence quantum yield of 80.1 and 84.9%, which resulted in high external quantum efficiency of 27.0 and 27.8% with color coordinates (0.148, 0.170) and (0.150, 0.230) in blue TADF organic light-emitting diodes, respectively. The high RISC rate and device efficiency inspired two TADF molecules to be used as sensitizers in hyperfluorescence devices. The hyperfluorescence devices showed ultra-high external quantum efficiency of 30.7 and 36.4% with color coordinates (0.125, 0.164) and (0.127, 0.193), respectively.

Stable and efficient all-inorganic quantum dot light-emitting diodes based on a double-layer electron transport layer

Abstract The most advanced quantum light-emitting diodes (QLEDs) have achieved almost unity external quantum efficiency (EQE) due to organic materials for high transport efficiency, but organic materials are less stable and can lead to irreversible degradation of the devices. The use of stable inorganic hole-transporting layers (HTLs), such as NiOx, becomes a promising alternative. ZnO is a common electron-transporting material in QLEDs, which possesses high mobility and tunable conductivity properties, but ZnO-based QLEDs devices undergo loss of efficiency due to exciton bursting, poor shelf stability, and pronounced positive aging effects. SnO2, as a common electron-transporting material, has better stability than ZnO. In this work, the SnO2/ZnO dual electron transport layer strategy is adopted, which can reduce the non-radiative burst and aging behavior, and at the same time, the electron transport is regulated by adjusting the film thickness. Inorganic QLEDs with high external quantum efficiency (9.5%) as well as high operational stability have been fully realized. This strategy provides effective ideas for future high-performance display devices.

Cascade Effect of a Dimerized Thermally Activated Delayed Fluorescence Dendrimer.

Thermally activated delayed fluorescence (TADF) emitters with a high horizontal orientation are highly essential for improving the external quantum efficiency (EQE) of organic light-emitting diodes; however, pivotal molecular design strategies to improve the horizontal orientation of solution processable TADF emitters are still scarce and challenging. Herein, a phenyl bridge is adopted to connect the double TADF units, and a dimerized TADF dendrimer, D4CzBNPh-SF, is successfully constructed. Compared to counterpart with single TADF unit, the proof-of-the-concept molecule not only exhibits an improved horizontal dipole ratio (78%) due to the π-delocalization-induced extended molecular conjugation, but also displays a faster reversed intersystem crossing rate constant (6.08×106 s-1) and a high photoluminescence quantum yield of 95% in neat film. Consequently, the non-doped solution-processed device with D4CzBNPh-SF as the emitter, achieves an ultra-high maximum EQE of 32.6%, which remains at 26.6% under a luminance of 1000 cd/m2. Furthermore, using D4CzBNPh-SF as a sensitizer, the TADF-sensitized fluorescence device exhibits a high maximum EQE of 30.7% at a luminance of 575 cd/m2 and a full width at half maximum of 36 nm.

Cascade Effect of a Dimerized Thermally Activated Delayed Fluorescence Dendrimer

Thermally activated delayed fluorescence (TADF) emitters with a high horizontal orientation are highly essential for improving the external quantum efficiency (EQE) of organic light‐emitting diodes; however, pivotal molecular design strategies to improve the horizontal orientation of solution processable TADF emitters are still scarce and challenging. Herein, a phenyl bridge is adopted to connect the double TADF units, and a dimerized TADF dendrimer, D4CzBNPh‐SF, is successfully constructed. Compared to counterpart with single TADF unit, the proof‐of‐the‐concept molecule not only exhibits an improved horizontal dipole ratio (78%) due to the π‐delocalization‐induced extended molecular conjugation, but also displays a faster reversed intersystem crossing rate constant (6.08×106 s‐1) and a high photoluminescence quantum yield of 95% in neat film. Consequently, the non‐doped solution‐processed device with D4CzBNPh‐SF as the emitter, achieves an ultra‐high maximum EQE of 32.6%, which remains at 26.6% under a luminance of 1000 cd/m2. Furthermore, using D4CzBNPh‐SF as a sensitizer, the TADF‐sensitized fluorescence device exhibits a high maximum EQE of 30.7% at a luminance of 575 cd/m2 and a full width at half maximum of 36 nm.

High‐Performance P‐N Junction Heterostructure with Carbon Quantum Dot and Nitrogen Self‐Doped Graphitic Carbon Nitride for Visible Light Photodetection

AbstractOrganic photodetectors (OPDs) hold immense promise for optoelectronic applications. Here a zero‐biased, high‐performance organic photodetector employing a 2D organic heterostructure is introduced. The structure combines carbon quantum dots (CQDs) with nitrogen self‐doped graphitic carbon nitride (g‐C3N4+) and is tested for alternating current (AC) photodetection on an interdigitated electrode platform. The study reveals extraordinary performance driven by the synergistic effects of efficient charge excitation, separation, and emission within the 2D/2D CQD/g‐C3N4+ heterostructure, leveraging mechanisms of photoconduction, photogating, and fluorescence. A unique convergence to similar rise and decay times in the order of 2.9 ms is observed at higher frequencies in the visible (Vis) spectrum. Benchmarking against state‐of‐the‐art OPDs shows ultrahigh specific detectivity (4.60 × 1018 Jones), ultrahigh responsivity (1.43 × 107 A W−1), high external quantum efficiency (43 × 107%) at an optical intensity of 3.56 × 10−4 mW cm−2 and a wavelength of 405 nm while delivering competitive performance at 532 and 635 nm as well. Moreover, a large linear dynamic range of 86–162 dB in the Vis spectrum is obtained. These enhancements promise development of a new generation of OPDs to advance light sensing and imaging applications at high frequency, marking a significant milestone in optoelectronic device engineering.

Fusion of Selenium‐Embedded Multi‐Resonance Units Toward Narrowband Emission and Fast Triplet‐Singlet Exciton Conversion

AbstractDeveloping multi‐resonance thermally activated fluorescence (MR‐TADF) emitters with both fast reverse intersystem crossing (RISC) rate and narrow emission bandwidth still remains a formidable challenge. Herein, a design strategy of fused MR skeleton containing heavy chalcogen (sulfur or selenium) for high‐performance MR‐TADF molecules is developed. Impressively, Se‐embedded emitter (DSeBN) shows extremely narrow full width at half maximum (FWHM) value of 16 nm and ultrafast RISC rate constant up to 2.0 × 106 s−1. The organic light‐emitting diode (OLED) based on this emitter exhibits excellent performance parameters with extremely narrow FWHM of 17 nm and high external quantum efficiency (EQE) of 35.31%. Significantly, much suppressed efficiency roll‐off is achieved, in which the EQE still stayed at 32.47% and 25.05% at the luminance of 100 and 1000 cd m−2, respectively. These results represent the state‐of‐the‐art device performance in terms of efficiency and FWHM, shedding new light on the development of practical MR‐TADF emitters.