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Solvent Effects on the Interface and Film Integrity of Solution-Processed ZnO Electron Transfer Layers for Quantum Dot Light Emitting Diodes
摘要： Solution-processed ZnO nanoparticle thin film is widely used as the electron transport layers (ETLs) in quantum dot light emitting diodes (QLEDs). While the ZnO nanoparticles (NPs) synthesis process has been thoroughly optimized, very few studies have focused on exploring how the solvents for dispersing the NPs affect the film-forming process, which has profound effects on the film quality and functionality as ETLs. Herein, we present a comprehensive investigation on the impact of the dispersing agent on the materials and carrier transport properties of spin-coated ZnO NP thin films. The first four members of the alkanol family, which show considerably different viscosities and volatilities, were used in this study. ZnO NP thin films deposited with different alcohols were used as the ETLs of the QLED structure and the optoelectronic performances of the devices are compared. Alcohols with high viscosity are found to cause NP agglomerations which roughen the film surface and lead to significant leakage current. Nano-cracks in the ZnO NP film are observed when a highly volatile solvent is used due to the vigorous bursts of vapor during solvent evaporation. Our results show that proper solvent can improve the surface roughness and compactness of the solution-processed ZnO films and lead to a 30% difference in the current efficiency of QLEDs. The findings here clearly indicate the important roles of the dispersing agent in the formation of high-quality NP-based thin films, which can be an important guidance for achieving high performances in QLEDs as well as a variety of solution-based devices.
关键词： Interface,Solvent,QLEDs,Electron transport layer,ZnO
更新于2025-11-21 11:01:37
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Highly Stable Red Quantum Dot Light Emitting Diodes with Long T <sub/>95</sub> Operation Lifetime
摘要： Quantum dot light-emitting diodes (QLEDs) with excellent performances such as external quantum efficiency (EQE) and lifetime have almost met the requirement of low brightness display. However, the short operation lifetime under high brightness limits the application of QLEDs in outdoor displays and lightings. Herein, we report a highly efficient, stable red QLED by using of lithium and magnesium co-doped as well as magnesium oxide shell-coated zinc oxide nanoparticle layer as electron transport layer (ETL). The optimized QLED has a high peak EQE of 20.6%, a low efficiency roll-off at high current, and a remarkably long lifetime T95 > 11000 h at 1000 cd m-2, which indicates the realization of the most stable red QLED up to now. The improvement in the long-term stability of the QLED is attributed to the use of co-doped and shell-coated zinc oxide ETL with reduced electron injection to improve the charge balance in device.
关键词： EQE,QLEDs,electron transport layer,ETL,magnesium oxide shell-coated zinc oxide,Quantum dot light-emitting diodes,external quantum efficiency,lithium and magnesium co-doped,ZLMO@MO,lifetime
更新于2025-09-23 15:21:01
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The Growth and Enhancement of Functional Ingredients for Health Improvement of Perilla Leaves Using LED Light Source with QD Application
摘要： Quantum dot (QD) has been used in various fields of mechanics and medical display. However, there is no studies of the application into agricultural fields. QD is an excellent source of the light production which is necessary for the plant growth. We demonstrated whether the application of Quantum dot lamps (QDLs) improves in quantity and quality of the perilla leaf production. Four types of QDLs which emit different wavelengths of lights were installed in the perilla greenhouse in Milyang, Korea. Our results showed that QDLs significantly increased in the perilla leaf growth compared with the control LED lamps. In addition HPLC analysis showed that perilla leaves exposed by Q2R lamps significantly increased contents of biologically functional components, such as chlorophyll, total flavonoid and phenolic-acid compounds, and several phenolic compounds (caffeic acid, coumaric acid, felulic acid and vanilic acid). The antioxidative capacity of perilla leaves extract varies depending on the type of QDLs. This is the first study providing important information regarding the application of quantum dot technology into the agricultural field.
关键词： QLEDs,perilla leaf,antioxidative capacity,functional components
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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Efficient Structure for InP/ZnS-Based Electroluminescence Device by Embedding the Emitters in the Electron-Dominating Interface
摘要： The charge-carrier distribution has been an important parameter in determining the efficiency of quantum-dot-based light-emitting diodes (QLEDs). In this Letter, we demonstrate a new inverted device structure of ITO/ZnO/polyethylenimine/quantum dots (QDs)/1,3,5-tris(N-phenylbenzimidazole-2-yl)benzene (TPBi)/4,4′-bis(9-carbazolyl)-2,2′-biphenyl (CBP)/MoO3/Al for improving the efficiency of InP-QD-based QLEDs. By introducing a thin layer of electron transport materials, the hole accumulation at the hole transport layer and the QD interface is largely reduced, which suppresses the quenching effect of holes on the QD emission. Compared with the conventional device structure with the emitters at ZnO/CBP pn junction, the peak current efficiency (external quantum efficiency) increases from 3.83 (5.17 cd/A) to 6.32% (8.54 cd/A) by imbedding the QDs at the electron-dominating interface of ZnO/TPBi. The analysis reveals that an internal quantum efficiency of nearly 100% is achieved for the InP-QD-based device (with a photoluminescence quantum yield of 32%). This work provides an alternative device structure for achieving high-efficiency QLED devices.
关键词： electron transport materials,quantum-dot-based light-emitting diodes,internal quantum efficiency,charge-carrier distribution,InP-QD-based QLEDs
更新于2025-09-23 15:19:57
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Highly luminescent blue-emitting In <sub/>1a??x</sub> Ga <sub/>x</sub> P@ZnS quantum dots and their applications in QLEDs with inverted structure
摘要： In order to resolve the issues of uncontrollably high reactivity of tris(trimethylsilyl)phosphine, widely used P precursor, and very low solubility of metal halide precursors in non-coordinating solvent with ligands in the synthesis of environmentally benign III-V quantum dots, we created bis(trimethylsilyl)phosphine, HP(TMS)2, new P precursor with controllable reactivity and new metal complex precursors (Indium-trioctylphosphine, In-TOP; Ga-TOP; Zn-TOP) soluble in octadecene, non-coordinating solvent with dodecanethiol, C12SH. Another challenging issue with III-V quantum dots is to generate highly luminescent photostable blue-emitting nanaocrystals. We present the way of synthesizing pure III-V In1-xGaxP blue-emitting alloy core in non-coordination solvent. Gallium is introduced in the core to adjust the exciton energy effectively and to lessen lattice mismatch with zinc sulfide shell which contributes to the removal of surface defects and the enhancement of the photostability, and thus enhancing the photoluminescent quantum yield (PLQY) and the high color purity of quantum dots with narrow full width at half maximum (FWHM). The blue-emitting quantum dots, In1-xGaxP@ZnS of outstanding quality (PLQY = 65 %, FWHM = 46 nm) is successfully synthesized with our new P and metal complex precursors. Furthermore, we apply those QDs to fabricate blue-emitting quantum dot light-emitting devices (QLEDs) with the external quantum efficiency of 0.20 % which is the best among the III-V-based blue-emitting QLEDs reported so far.
关键词： III-V semiconductors,Photoluminescence,Blue-emitting,QLEDs,Quantum dots
更新于2025-09-23 15:19:57
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Yb:MoO3/Ag/MoO3 Multilayer Transparent Top Cathode for Top-Emitting Green Quantum Dot Light-Emitting Diodes
摘要： In this study, we report on the application of a dielectric/ultra-thin metal/dielectric (DMD) multilayer consisting of ytterbium (Yb)-doped molybdenum oxide (MoO3)/silver (Ag)/MoO3 stacked as the transparent cathode in top-emitting green quantum dot light-emitting diodes (QLED). By optimizing the Yb doping ratio, we have highly improved the electron injection ability from 0.01 to 0.35. In addition, the dielectric/ultra-thin metal/dielectric (DMD) cathode also shows a low sheet resistance of only 12.2 ?/sq, which is superior to the resistance of the commercially-available indium tin oxide (ITO) electrode (~15 ?/sq). The DMD multilayer exhibits a maximum transmittance of 75% and an average transmittance of 70% over the visible range of 400–700 nm. The optimized DMD-based G-QLED has a smaller current leakage at low driving voltage. The optimized DMD-based G-QLED enhances the current density than that of G-QLED with indium zinc oxide (IZO) as a cathode. The fabricated DMD-based G-QLED shows a low turn-on voltage of 2.2 V, a high current e?ciency of 38 cd/A, and external quantum e?ciency of 9.8. These ?ndings support the fabricated DMD multilayer as a promising cathode for transparent top-emitting diodes.
关键词： QLEDs,DMD,top-emission,transparent cathode
更新于2025-09-19 17:13:59
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More Than 9% Efficient ZnSeTe Quantum Dot-Based Blue Electroluminescent Devices
摘要： We explore both synthesis of Cd-free blue quantum dots (QDs) with high-quality photoluminescence (PL) characteristics and fabrication of high-efficiency QD-light-emitting diodes (QLEDs). True blue (445 nm)-emissive, multishelled ZnSeTe QDs with a high PL quantum yield of 84% and sharp bandwidth of 27 nm are prepared. To obtain a better electron transport layer (ETL) material, surface of ZnMgO nanoparticles (NPs) is modified by additional Mg reaction, leading to the possible formation of Mg(OH)2 layer on the surface-modified ZnMgO (m-ZnMgO) NPs. The presence of Mg(OH)2 overlayer, origin for the desirably reduced electron mobility, is supposedly responsible for the improved charge balance of QD emissive layer (EML). The Mg(OH)2 layer is further found to alleviate the emission quenching of QD EML. Combining blue ZnSeTe QDs and m-ZnMgO NP ETL, highly bright, efficient blue QLEDs with the record luminance of 2904 cd/m2 and external quantum efficiency of 9.5% are demonstrated.
关键词： electron transport layer,Mg(OH)2 overlayer,electroluminescent devices,photoluminescence,ZnSeTe QDs,Cd-free blue quantum dots,QLEDs,ZnMgO nanoparticles
更新于2025-09-19 17:13:59
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All-solution Processed High Performance Inverted Quantum Dot Light Emitting Diodes
摘要： All-solution processed colloidal quantum dot light emitting diodes (QLEDs) with record performance have been successfully realized by introducing dually-doped poly(ethylenedioxythiophene)/polystyrenesulfonate (PEDOT:PSS) hole-injection layer and polyethylenimine (PEI) interfacial layer. Doping PEDOT:PSS with both Zonyl and isopropanol (IPA) significantly improves the wettability of PEDOT:PSS, making coating hydrophilic PEDOT:PSS onto hydrophobic hole-transporting layer poly(9-vinlycarbazole) (PVK) possible. The PEI interlayer between PVK/QD layer not only lowers down the vacuum level, thereby reducing the hole-injection barrier to balance the charge carriers, but also passivates QD surface defects via its amine group to suppress fluorescence quenching. As a result, the peak current efficiency of 28.1 cd/A, 43.1 cd/A, and 1.26 cd/A, the maximum external quantum efficiency (EQE) of 20.6%, 10.4%, and 2.95%, and the maximum luminance of 5.06 × 104 cd/m2, 1.21 × 105 cd/m2, and 2.96 × 103 cd/m2, have been achieved for red, green, and blue QLEDs, respectively. To the best of our knowledge, the red device’s EQE is one of the highest among all inverted red QLEDs. In addition, the extrapolated lifetime of the red QLEDs sets a new record by reaching 8253 h at an initial brightness of 100 cd/m2.
关键词： PEDOT:PSS,inverted structure,QLEDs,all-solution processed,quantum dot light emitting diodes,PEI
更新于2025-09-19 17:13:59
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Photophysics and electroluminescence of red quantum dots diluted in a thermally activated delayed fluorescence host
摘要： A feasible, universal, and low-cost strategy for quantum dot light-emitting devices (QLEDs) was provided to significantly enhance the electroluminescent performances. The emissive layer consists of organic host materials and quantum dots (QDs), and then the efficient energy transfer process remarkably promotes the device performances. It is confirmed that a highly efficient QLED can be realized by a host–guest system without common hole transport layers. The red device based on the thermally activated delayed fluorescence host and QD guest achieved a peak external quantum efficiency of 7.4%. Further, by simply modifying PEDOT:PSS with poly(4-styrenesulfonic acid), the work-function can be easily elevated, accompanied with the boosted external quantum efficiency to 11.9%. It is believed that such performances originate simultaneously from reduced interfacial fluorescence quenching, elevated work-function and efficient F?rster resonance energy transfer in the host–guest system.
关键词： external quantum efficiency,electroluminescent performances,quantum dot light-emitting devices,QLEDs,thermally activated delayed fluorescence,F?rster resonance energy transfer,host–guest system
更新于2025-09-16 10:30:52