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High‐Resolution Inkjet Printing of Quantum Dot Light‐Emitting Microdiode Arrays
摘要： The direct printing of microscale quantum dot light-emitting diodes (QLEDs) is a cost-effective alternative to the placement of pre-formed LEDs. The quality of printed QLEDs currently is limited by nonuniformities in droplet formation, wetting, and drying during inkjet printing. Here, optimal ink formulation which can suppress nonuniformities at the pixel and array levels is demonstrated. A solvent mixture is used to tune the ejected droplet size, ensure wetting, and provoke Marangoni flows that prevent coffee stain rings. Arrays of green QLED devices are printed at a resolution of 500 pixels in.?1 with a maximum luminance of ≈3000 cd m?2 and a peak current efficiency of 2.8 cd A?1. The resulting array quality is sufficient to print displays at state-of-the-art resolutions.
关键词： light-emitting diodes,quantum dots,uniform pixel arrays,inkjet printing,high resolution
更新于2025-09-11 14:15:04
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Correlation between the Morphology of ZnO Layers and the Electroluminescence of Quantum Dot Light-Emitting Diodes
摘要： The present work shows the e?ect of the ZnO layer morphology on inverted quantum dot light-emitting diodes (QLEDs) using di?erent spin-coating processes. In the inverted structure of ITO/ZnO/QDs/CBP/MoO3/Al, ZnO nanoparticles were used as the electron transport layer. The utilization of a two-step spin-coating process to deposit a ZnO layer on a patterned ITO glass substrate resulted in an increase in the surface roughness of the ZnO layer and a decrease in the luminance of the QLEDs. However, the current e?ciency of the device was enhanced by more than two-fold due to the reduced current density. Optimization of the ZnO spin-coating process can e?ciently improve the optical and electrical properties of QLEDs.
关键词： colloidal quantum dots,quantum dot light-emitting diodes,spin-coating process,ZnO
更新于2025-09-11 14:15:04
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Recent Advances in Conjugated TADF Polymer Featuring in Backbone-Donor/Pendant-Acceptor Structure: Material and Device Perspectives
摘要： Along with the persistent research interest in organic light-emitting diode (OLED) display and lighting technology, a new studying topic is now focused on developing thermally activated delayed fluorescence (TADF) polymer emitters, with the purpose to achieve high-performance cost-effective, solution-processed OLEDs (s-OLEDs) purely from fluorescent-type materials. However, research in this topic is in its infancy about the designing rules of polymer structures, photophysical mechanisms and the correlated devices. In this Personal Account, mainly from our personal experience we will shortly introduce the historical developments, status and perspectives about one representative kinds of TADF polymers, i. e. the conjugated TADF polymers featuring in backbone-donor/pendant-acceptor (BDPA) structure scaffold, which shows very promising electroluminescent (EL) performance even using simple s-OLED structure. Special attention is focused on illustrate the molecular designing & synthesis motivation, chemistry & device tactics towards solving the limiting factors about the quantum yields and aggregation-quenching tendency in solid states. Further challenges and strategies towards optimizing their overall EL performance, e. g. simultaneous achieving extremely high external quantum efficiency, power efficiency and low roll-off rate, are also discussed.
关键词： thermally activated delayed fluorescence,exciplex,solution-processed,polymer,organic light-emitting diodes
更新于2025-09-10 09:29:36
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Reference Module in Chemistry, Molecular Sciences and Chemical Engineering || Deposition, Ligand Removal, and Applications of Atomically Precise, Chemically Synthesized Clusters on Metal Oxide Surfaces
摘要： It is now well established that the properties of metal particles can undergo dramatic changes in properties when they are reduced to the nanometer size regime. It is furthermore evident that these property changes become even more marked below 2 nm, into the nonscalar size regime. Such ultra-small “metal clusters” (also called “nanoclusters”) exhibit dynamic ?uxionality; thus they can barely be de?ned by one single shape. Moreover, their properties are observed to change with the addition or removal of just a single atom. These dramatic changes with cluster size arise because of the molecular-like energy levels present. These energy levels can not only affect the physical properties of the cluster but also its chemical reactivity and so there is a great expectation emerging that metal clusters could act as super-ef?cient catalysts.
关键词： light-emitting diodes,photocatalysis,nanoclusters,catalysis,metal clusters,photovoltaics,sensors
更新于2025-09-10 09:29:36
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One-step hydrothermal synthesis of carbon dots-polymer composites with solid-state photoluminescence
摘要： Carbon dots (CDs) and CDs-polymer composites were one-step synthesized in a hydrothermal process using hexamethylenetetramine and polycarbonate as precursors. Their optical properties and the application as solid-state phosphors towards white light-emitting diodes (LEDs) were thoroughly investigated. CDs solutions exhibit strong yellow emission under blue illumination and possess excitation-independent luminescent behavior. Owing to precursor polymerization, CDs-polymer composites were synthesized in one step. The dried CDs-polymer composite powders exhibit excellent optical stability and no luminescence quenching was observed. Under light blue illumination, the powders show broad yellow luminescence with the peak wavelength centered at 550 nm and PL quantum yield of 14.86%. For their practical applications, stable white light emission was demonstrated by coating a 455nm blue LED with the powders. Our research offers a valuable reference for growing CDs-polymer composites in a facile, low-cost and low-temperature hydrothermal process and developing white LEDs with light blue LEDs and metal-free phosphors.
关键词： white light-emitting diodes (LEDs),phosphors,solid-state photoluminescence,hydrothermal method,carbon materials,luminescence
更新于2025-09-10 09:29:36
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Raising the Operating Temperature of (Ga,Mn)As/GaAs Spin Light Emitting Diodes by Applying Post-Growth Treatment
摘要： Spin light emitting diodes (spin-LEDs) containing (Ga,Mn)As ferromagnetic layers are fabricated based on InGaAs/GaAs heterostructures and studied. We achieve increases in the operating temperatures of our spin-LEDs by subjecting the surface of the structures, prior to depositing an ohmic metal contact, to pulsed laser annealing. The fabricated devices produce circularly polarized electroluminescence when placed in an external magnetic field. The temperatures at which circularly polarized electroluminescence is still observed is raised from 30 K for unprocessed structure to 110 K for laser-annealed structures. The observed effect is linked to an increase in the Curie temperature of the (Ga,Mn)As layer as a result of laser impact.
关键词： ferromagnetic layers,circularly polarized electroluminescence,Curie temperature,Mn)As,pulsed laser annealing,Spin light emitting diodes,(Ga
更新于2025-09-10 09:29:36
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Reference Module in Materials Science and Materials Engineering || III-Nitride-Based Short-Wavelength Ultraviolet Light Sources
摘要： Group-III-nitride-based short-wavelength ultraviolet (UV) light sources, such as laser diodes (LDs) and light-emitting diodes (LEDs), with active region comprising AlInGaN material system that can emit light at a wavelength shorter than 400 nm, are of extreme interest because of their current applications and future prospects of newer and improved applications. Owing to its compactness, lower cost, and environmental friendly composition, UV LEDs are expected to replace traditional lamps and also will pave the way for opening up many new applications, especially portable ones.
关键词： III-Nitride,Laser diodes,Ultraviolet,Light-emitting diodes,AlInGaN
更新于2025-09-09 09:28:46
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Deep-blue light-emitting polyfluorenes with asymmetrical naphthylthio-fluorene as Chromophores
摘要： A novel blue polycyclic aromatic compound 2,8-dibromo-14,14-dioctyl-14H-benzo[b]benzo [5,6] fluoreno[1,2-d] thiophene 9,9-dioxide (Br2NFSO) is designed and synthesized through multistep synthesis, and its structure is confirmed by nuclear magnetic resonance. Based on synthesized polycyclic aromatic compound Br2NFSO, a series of twisted blue light-emitting polyfluorenes derivatives (PNFSOs) are prepared by one-pot Suzuki polycondensation. Based on the twisted polymer molecular structure resulted from the asymmetric links of 14,14-dioctyl-14H-benzo[b]benzo[5,6]fluoreno [1,2-d]thiophene 9,9-dioxide (NFSO) unit in copolymers and better electron transport ability of NFSO than those of the electron-deficient dibenzothiophene-S,S-dioxide counterpart, the resulting polymers exhibit excellent electroluminescent spectra stability in the current densities from 100 to 800 mA cm?2, and show blue-shifted and narrowed electroluminescent spectra with the Commission Internationale de L0Eclairage (CIE) of (0.16, 0.07) for PNFSO5, compared to poly(9,9-dioctylfluorene) (PFO) with the CIE of (0.18, 0.18). Moreover, the superior device performance is achieved based on PNFSO5 with the maximum luminous efficiency (LEmax) of 1.96 cd A?1, compared with the LEmax of 0.49 cd A?1 for PFO. The results indicate that the twisted polycyclic aromatic structure design strategy has a great potential to tuning blue emission spectrum and improving EL efficiency of blue light-emitting polyfluorenes.
关键词： twisted structure,polycyclic aromatic compound,polymer light-emitting diodes,intromolecular charge transfer,synthesis
更新于2025-09-09 09:28:46
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Phenyl and Pyrazolyl Functionalized Pyrimidine: Versatile Chromophore of Bis-Tridentate Ir(III) Phosphors for Organic Light Emitting Diodes
摘要： There is a growing interest in the bis-tridentate Ir(III) emitters as they are expected to display both the improved emission efficiency and photostability. Herein, we turned to the new emitters m2h-1 - 3 and m6h-1 - 3, bearing a pincer carbene ancillary and a chromophoric chelate derived from judiciously selected phenyl-pyrimidine-pyrazole entities (pzm2hF)H2 or (pzm6hF)H2, which differ in terms of the location of phenyl and pyrazole substituents on central pyrimidine. DFT calculations revealed a notable change of spin density distribution from the pyrimidine-pyrazolate entity in m2h to pyrimidine-phenyl fragment in m6h. As a consequence, the m6h emitters exhibited both the shortened emission lifetime and improved stability under extensive photolysis in solution, while corresponding OLEDs doped with green emitting m6h-1 and sky-blue emitting m6h-2 and m6h-3 exhibited external quantum efficiencies of 17.6%, 15.9% and 17.6%, superior to all their m2h counterparts at a practical luminance of 103 cd/m2. This finding suggests a new methodology in fine-tuning the electronic transition that is important to high-performance and durable phosphorescent OLEDs.
关键词： phosphorescent OLEDs,organic light emitting diodes,bis-tridentate Ir(III) emitters,photostability,pyrimidine
更新于2025-09-09 09:28:46
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Decoration of Dibenzofuran Using Cyanocarbazole via 6‐ Position As a Molecular Design Approach for High Triplet Energy Bipolar Host Materials
摘要： In this study, two new dibenzofuran derivatives featuring one or two cyanocarbazole units, 6-(dibenzo[b,d]furan-4-yl)-9-phenyl-9H-carbazole-3-carbonitrile (mBFCzCN) and 6,6'-(dibenzo[b,d]furan-4,6-diyl)bis(9-phenyl-9H-carbazole-3-carbonitrile) (dBFCzCN), were developed as host materials for phosphorescent organic light emitting diodes (PhOLEDs). A new molecular design connecting the cyanocarbazole to the dibenzofuran using the cyanocarbazole 6-position instead of its 9-position was created, and the effects of number of cyanocarbazole units in the dibenzofuran building block on the photophysical and electroluminescence properties were investigated in detail. The mBFCzCN compound revealed high triplet energy (2.78 eV) than that of dBFCzCN (2.68 eV) and good bipolar charge transporting properties. The potential of these materials as hosts for blue and green PhOLEDs was investigated using bis(4,6-(difluorophenyl)pyridinato-N,C2’)picolinate iridium(III) (FIrpic) and tris(2-phenylpyridinato)iridium(III) (Ir(ppy)3) dopants, respectively. The results indicated that the mBFCzCN with one cyanocarbazole unit showed better device performance than the dBFCzCN with two cyanocarbazole units in the blue and green devices. High external quantum efficiencies of 19.0 and 21.2% were demonstrated in the blue and green PhOLEDs with the mBFCzCN host due to its high triplet energy and good bipolar charge transporting characteristics.
关键词： phosphorescent organic light emitting diodes,dibenzofuran,cyanocarbazole,host materials,bipolar charge transporting,triplet energy
更新于2025-09-09 09:28:46