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Enhancing Reverse Intersystem Crossing via Secondary Acceptors: towards Sky-Blue Fluorescent Diodes with Tenfold-Improved Exter-nal Quantum Efficiency
摘要： How to simply but effectively facilitate reverse intersystem crossing (RISC) transition is always the key issue for developing high-performance thermally activated delayed fluorescence (TADF) dyes. In this work, as a proof of concept, a feasible strategy named 'acceptor enhancement' is demonstrated with a series of ternary blue emitters (xCzmPOnTPTZ) using diphenylphosphine oxide (PO) as secondary acceptors. Compared with its PO-free binary analogue, such simple introduction of PO groups in pCzPO2TPTZ dramatically enhances its RISC rate constant (kRISC) by 10 times to the level of ~105 s-1, accompanied by RISC efficiency (ηRISC) of 92%, which further improves the triplet-to-singlet upconversion for effective triplet harvesting in its devices. As the result, on the basis of a trilayer device structure, pCzPO2TPTZ realized a state-of-the-art external quantum efficiency (EQE) beyond 20% with tenfold improvement.
关键词： Organic Light-Emitting Diode,Thermally Activated Delayed Fluorescence,Excited State Transition,Blue Emission,Reverse Intersystem Crossing,Phosphine Oxide Acceptor
更新于2025-09-23 15:23:52
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Syntheses, X-Ray Crystal Structures, Emission Properties and DFT Calculations of Monoprotonated Polypyridines
摘要： Monoprotonated compounds [(L)HPF6] were prepared by the reaction of (L = bpy, phen, dpphen, bqn and ppy) with concentrated HCl in water. Monoprotonated pyridine rings are hydrogen bonded intramolecularly to the adjacent pyridine ring and intermolecularly to the adjacent PF6- in compounds. These hydrogen bonds restrain the nonradiative decay to produce intense emission. Density functional theory was applied to interpret the planarity in compounds. The attachment of one proton to the nitrogen in [(dpphen)HPF6] and [(bqn)HPF6] leads to the strong emission in acetonitrile (Φ = 0.046 and 0.097, respectively). In particular, the attachment of one proton to the ppy nitrogen results in exhibiting a strong emission with a large quantum yield (Φ = 0.264).
关键词： crystal structure,DFT calculations,blue emission,monoprotonated polypyridine
更新于2025-09-23 15:22:29
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Blue-emitting Photostable Hybrid Films for High-efficiency Large-area Light Converter and Photonic Applications
摘要： A blue fluorophore of Schiff base zinc complex is prepared by a hydrolysis-free solution-based synthetic method. Under UV excitation, the complex produces blue emission with a quantum yield (Q) of 42.6% in methylene chloride and 24.0% in standalone powder form. Quantum mechanical calculations show that the blue emission is generated by the change in the chemical state of the ligand associated with the complexation with Zn cations. Thin films of Zn complexes incorporated in polymethylmethacrylate (PMMA) and cellulose acetate butyrate (CAB) polymers are also prepared by dispersing the complexes into the polymer matrices. These hybrid polymer films exhibit several notable features, particularly enhanced luminescence efficiency (with maximum Q of 85.8% for PMMA and 30.0% for CAB) and scalability for fabrication over a large area while retaining the original properties of the host polymers. Light-emitting diodes are also fabricated using the CAB hybrid thin films, and they show a Q of 43.2% with excellent photostability. The complex and its hybrid films demonstrate their great potential for such applications as UV-to-blue conversion devices in photoelectronics, solar-cell concentrators, solid-state lighting and display, and green-house agriculture.
关键词： blue emission,photostable hybrid films,Schiff base,Fluorescent polymer films
更新于2025-09-23 15:21:21
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Bright Blue Light Emission of Ni2+ ions doped CsPbClxBr3-x Perovskite Quantum Dots Enabling Efficient Light-Emitting Devices
摘要： In recent years, significant advances have been achieved in the red and green perovskite quantum dots（PQDs）based light-emitting diodes (LEDs). However, the performances of the blue perovskite LEDs are still seriously lagging behind that of the green and red counterparts. Herein, we successfully developed Ni2+ ions doped CsPbClxBr3-x PQDs through the room-temperature supersaturated recrystallization synthetic approach. We simultaneously realized the doping of various concentrations of Ni2+ cations, and modulated the Cl/Br element ratios through introducing different amount of NiCl2 solution in the reaction medium. By the synthetic method, not only the emission wavelength from 508 to 432 nm of Ni2+ ions doped CsPbClxBr3-x QDs was facially adjusted, but also the photoluminescence quantum yield (PLQY) of PQDs was greatly improved due to efficiently removing the defects of the PQDs. Thus, the blue emission at 470 nm with PLQY of 89% was achieved in 2.5% Ni2+ ions doped CsPbCl0.99Br2.01 QDs, which increased nearly three times over that of undoped CsPbClBr2 QDs, and was the highest for the CsPbX3 PQDs with blue emission that fulfilling the NTSC standards. Benefiting from the high luminous Ni2+ ions doped PQDs, the blue emitting LED at 470 nm was obtained, exhibiting an external quantum efficiency (EQE) of 2.4% and a maximum luminance of 612 cd/m2, which surpassed the best performance reported previously for the corresponding blue-emitting PQDs based LED.
关键词： perovskite QD-LEDs,Ni2+ ion doping,blue emission,anion exchange,perovskite quantum dots
更新于2025-09-23 15:21:01
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Surface Regulation of CsPbBr <sub/>3</sub> Quantum Dots for Standard Blue-Emission with Boosted PLQY
摘要： It is demonstrated that, via surface treatment of CsPbBr3 perovskite quantum dots (PeQDs) by introducing small amount of organic ammonium chlorides possessing short alkyl chain (C ≤ 4) in methyl acetate in the typical purification process, the emission can be tuned from green to blue region with boosted photoluminescence quantum yield (PLQY). The Cl? mainly works on the surface of PeQDs to fill bromide vacancy, which generates a passivated mixed-halide surface and avoids formation of defects deep within bandgap. Meanwhile, the replacement of initial long-chain ligands with short chain ammonium moiety benefits the film PLQY. Accordingly, a standard blue emission of 461 nm with a high film PLQY of 52% is accessed and the corresponding colloidal shows a PLQY of 80% at 456 nm. This method is also proved to be a versatile tool to boost the PLQY of PeQDs by using short chain ammonium halides bearing the same X with the initial CsPbX3. A near-unity colloidal PLQY of 97% and 98% is achieved for CsPbBr3 and CsPbI3 respectively. Quantum dots light-emitting diode (QLED) with treated CsPbBr3 affords a standard blue electroluminescence of 459 nm and a maximum external quantum efficiency of 0.3%.
关键词： perovskite quantum dots,vacancy passivation,surface regulation,standard blue emission
更新于2025-09-23 15:21:01
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ZnSe:Te/ZnSeS/ZnS Nanocrystals: An Access to Cadmium-Free Pure-Blue Quantum-Dot Light-Emitting Diodes
摘要： Cadmium-free quantum dots (QDs) are attracting considerable research attention because of their low toxicity. However, the bandgap of most cadmium-free QDs avoids the pure-blue region, which confers difficulty in realizing pure-blue quantum-dot light-emitting diodes (QLEDs). In this work, we successfully tuned the emission wavelength of ZnSe/ZnS quantum dots from the violet region (~ 420 nm) to the pure-blue region (450 – 460 nm) by doping Te into the ZnSe core. The ZnSe:0.03Te/ZnSeS/ZnS QDs sample with an emission position of 450 nm and quantum yield of 30% was the most balanced formula. To overcome the energy gap between the hole-transfer layer and QD layers, a specific hole-transfer layer was developed for normal-structure QLEDs. Such structure QLED by ZnSe:0.03Te/ZnSeS/ZnS QDs achieved the pure-blue light emission at 455 nm, a low turn-on voltage of 4.4 V, and external quantum efficiency of 0.33%. Overall, our cadmium-free QLED achieved pure-blue emission, revealing the potential of ZnSe-based pure-blue QLEDs for future displays.
关键词： Pure-blue emission,Cadmium-free,QLEDs,Quantum dots,ZnSe
更新于2025-09-23 15:21:01
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Optimization of Quantum Yield of Highly Luminescent Graphene Oxide Quantum Dots and Their Application in Resistive Memory Devices
摘要： A facile chemical method of acid treatment has been followed for the cutting of graphene oxides (GOs) sheet to extract graphene oxide quantum dots (GOQDs) in aqueous medium at different pH. Strong blue emission and excitation dependent photoluminescence (PL) spectrum are observed in GOQDs synthesized at pH11. Presence of defect related states and oxygen containing functional groups in GOQDs are confirmed through Raman and fourier transform infrared (FTIR) analysis, respectively. High resolution transmission electron microscopy (HR-TEM) analysis suggests that the sizes of GOQDs are distributed in the range ~2.0 to 8.0 nm with d-spacing of 0.245 nm. AFM measurement confirms the topography height of GOQDs in the range ~ 6.0-9.0 nm. Synthesized GOQDs at different pH are dispersed in poly (vinyl alcohol) (PVA) matrix and spin coated to fabricate polymer nanocomposites (PNCs) devices. Electrical studies have been performed which display write-once-read-many (WORM) characteristics and the set voltage (????????) increases with the increase in pH of the GOQDs. Very low ???????? ~ - 0.9 V and ??????/???????? ~104 have been obtained for the device containing GOQDs synthesized at pH1. Retention tests up to 104 s are performed for the PNCs devices in order to confirm the stability. A suitable energy band diagram is proposed to discuss the carrier transport through the composites devices.
关键词： Polymer nanocomposites,GOQDs,Blue emission,WORM,Quantum yield
更新于2025-09-23 15:19:57
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trans-N-(Heterocyclic Carbene) Platinum(II) Acetylide Chromophores as Phosphors for OLED Applications
摘要： A family of complexes of the type trans-(NHC)2Pt(C≡C-Ar)2 (NHC = N-heterocyclic carbene and Ar = substituted phenyl or 4-pyridyl) exhibits blue or blue-green phosphorescence. The photoluminescence is 10 – 50 fold more efficient when the materials are in dispersed in a solid poly(methyl methacrylate) glass compared to in THF solution. The phosphorescence quantum efficiencies in PMMA glass range from 0.20 – 0.65, varying with the structure of the aryl acetylide ligands. Organic light emitting diodes (OLEDs) were fabricated by thermal evaporation, using bis[2-(diphenylphosphino)phenyl] ether oxide (DPEPO) as the host and 15% of the trans-(NHC)2Pt(C≡C-Ar)2 complexes as the dopant/emitters. Most of the OLEDs display good performance, with EL spectra that closely match the PL in the PMMA glass. The best performing materials have peak EQE ranging from 9.6 – 14.1%, with deep blue spectral profiles (minimum CIE (0.16,0.13). Several of the complexes have deep HOMO levels and they display poor EL performance attributed to inefficient host to emitter hole transfer.
关键词： OLED,blue emission,platinum acetylide,platinum N-heterocyclic carbene,phosphor
更新于2025-09-23 15:19:57
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Highly efficient non-doped blue fluorescent OLEDs with low efficiency roll-off based on hybridized local and charge transfer excited state emitters
摘要： Designing a donor-acceptor (D-A) molecule with a hybridized local and charge transfer (HLCT) excited state is a very effective strategy for producing an organic light-emitting diode (OLED) with a high exciton utilization efficiency and external quantum efficiency. Herein, a novel twisting D-π-A fluorescent molecule (triphenylamine-anthracene-phenanthroimidazole; TPAAnPI) is designed and synthesized. The excited state properties of the TPAAnPI investigated through photophysical experiments and density functional theory (DFT) analysis reveal that its fluorescence is due to the HLCT excited state. The optimized non-doped blue OLED using TPAAnPI as light-emitting layer exhibits a novel blue emission with an electroluminescence (EL) peak at 470 nm, corresponding to the Commission International de L’Eclairage (CIE) coordinates of (0.15, 0.22). A fabricated device termed Device II exhibits a maximum current efficiency of 18.09 cd A ?1, power efficiency of 12.35 lm W?1, luminescence of ≈29900 cd cm?2, and external quantum efficiency (EQE) of 11.47%, corresponding to a high exciton utilization efficiency of 91%. Its EQE remains as high as 9.70% at a luminescence of 1000 cd m?2 with low efficiency roll-off of 15%. These results are among the best for HLCT blue-emitting materials involved in non-doped blue fluorescent OLEDs. The performance of Device II highlights a great industrial application potential for the TPAAnPI molecule.
关键词： HLCT,efficiency roll-off,blue emission,non-doped,OLED
更新于2025-09-23 15:19:57
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The effect of templates on the morphological and optical properties of BaMgAl10O17:Eu2+ phosphors
摘要： Blue light emitting BaMgAl10O17:Eu2+ phosphors were prepared by solution combustion synthesis method using urea as a fuel. Water-soluble templates, β-cyclodextrin and thioglycerol were used for the synthesis process. The main aim of the present work is to study the effect of these templates on morphology and optical properties of BaMgAl10O17:Eu2+ phosphor. The inclusion of templates prevents agglomeration, hence improving crystallinity and photoluminescence emission intensity. β-cyclodextrin and thioglycerol modified the morphology of BaMgAl10O17:Eu2+ phosphor by transforming its multifaceted plate-like to rod-like morphology. It is observed that the addition of β-cyclodextrin and thioglycerol in the synthesis of BaMgAl10O17:Eu2+ phosphor not only increased the photoluminescence emission of BaMgAl10O17:Eu2+ phosphor but also enhanced the thermal stability of the BaMgAl10O17:Eu2+ phosphor. Hence the use of β-cyclodextrin and thioglycerol was beneficial in improving the crystallinity, photoluminescence characteristics and the thermal stability of BaMgAl10O17:Eu2+ phosphor.
关键词： blue emission,photoluminescence,thermal stability,europium,polymer
更新于2025-09-23 15:19:57