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The effects of chemical treatment on ITO properties and performance of OLED devices
摘要： In this work, chemical treatment was performed on the surfaces of two types of indium tin oxides (ITOs) with different physical properties. The effects of the chemical treatment on the physical parameters of the ITOs, and on the efficiency of the organic light emitting diodes (OLEDs) fabricated on the ITOs, were then examined. The ITO substrates were characterized via X-ray diffraction, atomic force microscopy, optical absorption, and electrical resistance measurement. The results showed that the chemical treatment exerted no significant changes on the structure and transparency of the wavelength of the light emitted from Alq3; however, the treatment improved the morphology and resistance of the ITOs examined. To serve the research purpose, the ITOs were first characterized, and then, the OLEDs were fabricated so that they would have a structure of Glass/ITO/PEDOT:PSS/Alq3/Al. The OLEDs were characterized current density, resistance, power, and irradiance as a function of the voltages. The results of the study showed decreases in the turn-on voltage (from 5.5 to 4 V for one of the OLEDs and 7 to 6 V for the other), resistance and power (for one of the ITOs), and irradiance (for one of the ITOs) due to the chemical treatment.
关键词： Chemical treatment,Organic light emitting diodes (OLEDs),ITO
更新于2025-09-23 15:21:01
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Understanding degradation of organic light-emitting diodes from magnetic field effects
摘要： The impact of magnetic field effects on the electroluminescence of organic light-emitting diodes is commonly used to characterize exciton dynamics such as generation, annihilation, and performance degradation. However, interpreting these effects is challenging. Here, we show that magnetic field effects in organic light-emitting diodes can be understood in terms of the magnetic response of device characteristics derived from polaron-pair and triplet exciton quenching processes, such as triplet-polaron interactions and triplet-triplet annihilation. Device degradation shows a clear relationship with the amplitude of the magnetic field effects, enabling non-destructive measurement of the degradation. The results and proposed mechanism provide a better understanding of magnetic field effects on organic light-emitting diodes and device degradation phenomena.
关键词： magnetic field effects,device degradation,organic light-emitting diodes,triplet-polaron interactions,triplet-triplet annihilation,exciton dynamics
更新于2025-09-23 15:21:01
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Synthesis and photoluminescence properties of Ca4La6(PO4)2(SiO4)4O2: Dy3+ phosphor with high thermal stability for white light-emitting diodes
摘要： Novel yellow emitting Ca4La6(PO4)2(SiO4)4O2: Dy3+ phosphors were synthesized by high-temperature solid-state reaction method. The crystal structure, diffuse reflection, photoluminescence, and photoluminescence excitation spectra, decay curves, as well as thermal stability were investigated in detail. Under 346?nm excitation, the phosphor exhibits two strong emission peaks at 479?nm and 585?nm, with the CIE coordinates located in the yellow region. When heated up to 150?°C, the Ca4La6(PO4)2(SiO4)4O2: 0.06Dy3+ phosphor still has 83% of the initial PL intensity at room temperature, indicating its high thermal stability. The results suggest that the as-prepared Ca4La6(PO4)2(SiO4)4O2: Dy3+ phosphor could serve as a promising candidate for near-ultraviolet white light-emitting diodes.
关键词： photoluminescence,Ca4La6(PO4)2(SiO4)4O2:Dy3+,thermal stability,white light-emitting diodes,phosphor
更新于2025-09-23 15:21:01
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Large Performance Enhancement in All-Solution-Processed, Full-Color, Inverted Quantum Dot Light-Emitting Diodes by Using Graphene Oxide-Doped Hole Injection Layer
摘要： Solution-processed hole injection layers (HILs) for full-color, inverted quantum dot light-emitting diodes (QLEDs) are developed by simply incorporating the graphene oxide (GO) into poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS). The excellent wettability of the GO-doped PEDOT:PSS mixture facilitates the effective deposition of HIL onto the organic underlayer. Ultraviolet photoelectron spectroscopy and Raman spectroscopy characterization reveal that the GO-doped PEDOT:PSS HIL possesses the advantages of increased work function and improved conductivity. Thus, the GO-doped PEDOT:PSS HIL can promote hole injection from the top anode into the device by reducing the hole injection barrier and sheet resistance. As a result, by using the GO-doped PEDOT:PSS HIL, we have successfully demonstrated highly bright all-solution-processed, full-color, inverted QLEDs showing remarkably enhanced luminance of 142165, 63318, and 3019 cd/m2 for green, red, and blue devices, respectively. To the best of our knowledge, the green device’s luminance is the best for all-solution-processed inverted green QLEDs. These results suggest that the GO-doped PEDOT:PSS is a promising candidate for high-quality HIL in all-solution-processed QLEDs with an inverted structure.
关键词： Optical,Quantum Dot Light-Emitting Diodes,Hole Injection Layer,Plasmonics,Magnetic,Hybrid Materials,Graphene Oxide,PEDOT:PSS
更新于2025-09-23 15:21:01
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Ultra-High Vacuum Annealing-Assisted Quantum Wells Dimensional Tailoring for Perovskite Light-Emitting Diodes Efficiency Enhancement
摘要： Quasi-two-dimensional (Q-2D) perovskites featured with multiple dimensional quantum wells (QWs) have been the main candidates for optoelectronic applications. However, the excessive low-dimensional perovskite is unfavorable to the device efficiency due to the phonon-exciton interaction and the inclusion of insulating large organic cation. Herein, the low-dimensional QWs formation is suppressed by removing the organic cation 1-naphthylmethylamine iodide (NMAI) through the ultra-high vacuum (UHV) annealing. The perovskite light-emitting diodes (PLEDs) devices based on films annealed with optimized UHV conditions show higher external quantum efficiency of 13.0% and wall-plug efficiency of 11.1% compared to otherwise identical devices with films annealed in a glovebox.
关键词： quantum wells,ultra-high vacuum annealing,dimensional tailoring,quasi-two-dimensional perovskites,perovskite light-emitting diodes
更新于2025-09-23 15:21:01
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Graphene for Flexible Lighting and Displays || Graphene-based quantum dot emitters for light-emitting diodes
摘要： Quantum dot is a zero-dimensional material that is introduced from the quantum con?nement effect when it is sized in nanometer scale and has various electrical and optical properties depending on the size of the particle. The electrons con?ned in small areas of nanoscale which are smaller than exciton Bohr radius are quantized and limited in free motion, and electrons in quantum dot are con?ned in every three direction by the quantum con?nement effect which causes a ?nite number of electron, hole, and exciton states, resulting in various characteristics on the size of the particle. In other words, the full con?nement in every three direction results in the complete quantization or discretization of the energy states of con?ned charge carriers in quantum dot [1]. Therefore, the fewer energy levels are quanti?ed as the energy level of the carrier decreases as the particle size decreases, resulting in a wider and more discretized bandgap [2e4].
关键词： electroluminescence,light-emitting diodes,quantum confinement,graphene quantum dots,photoluminescence
更新于2025-09-23 15:21:01
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Manganese doping stabilizes perovskite light-emitting diodes by reducing ion migration
摘要： Lead halide perovskite light-emitting diodes have recently emerged as high-performance devices. However, they degrade rapidly. This degradation has been attributed to the mixed ionic-electronic nature of these perovskites. Manganese doping increases the stability of perovskite light-emitting diodes, but the effects of manganese doping on ion migration are not well understood. We use impedance spectroscopy and transient ion-drift measurements to study the effect of manganese doping on ion migration in PEABr0.2Cs0.4MA0.6PbBr3 quasi-bulk 2D/3D perovskite light-emitting diodes. We find that manganese doping enhances the activation energy for ion migration two fold and reduces the diffusion coefficient. These changes in the behavior of mobile ions help to explain the improved stability in perovskite light-emitting diodes upon manganese doping and lead to a better understanding of the influence of passivating agents on ion migration and thus on the stability of the devices.
关键词： capacitance,perovskites,manganese,mobile ions,transient ion drift,impedance,light-emitting diodes
更新于2025-09-23 15:21:01
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Al-, Ga-, Mg-, or Li-doped zinc oxide nanoparticles as electron transport layers for quantum dot light-emitting diodes
摘要： Colloidal quantum dots and other semiconductor nanocrystals are essential components of next-generation lighting and display devices. Due to their easily tunable and narrow emission band and near-unity fluorescence quantum yield, they allow cost-efficient fabrication of bright, pure-color and wide-gamut light emitting diodes (LEDs) and displays. A critical improvement in the quantum dot LED (QLED) technology was achieved when zinc oxide nanoparticles (NPs) were first introduced as an electron transport layer (ETL) material, which tremendously enhanced the device brightness and current efficiency due to the high mobility of electrons in ZnO and favorable alignment of its energy bands. During the next decade, the strategy of ZnO NP doping allowed the fabrication of QLEDs with a brightness of about 200 000 cd/m2 and current efficiency over 60 cd/A. On the other hand, the known ZnO doping approaches rely on a very fine tuning of the energy levels of the ZnO NP conduction band minimum; hence, selection of the appropriate dopant that would ensure the best device characteristics is often ambiguous. Here we address this problem via detailed comparison of QLEDs whose ETLs are formed by a set of ZnO NPs doped with Al, Ga, Mg, or Li. Although magnesium-doped ZnO NPs are the most common ETL material used in recently designed QLEDs, our experiments have shown that their aluminum-doped counterparts ensure better device performance in terms of brightness, current efficiency and turn-on voltage. These findings allow us to suggest ZnO NPs doped with Al as the best ETL material to be used in future QLEDs.
关键词： electron transport layer,doping,zinc oxide nanoparticles,light-emitting diodes,quantum dots
更新于2025-09-23 15:21:01
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Tunable Chromaticity and High Color Rendering Index of WLEDs with CaAlSiN <sub/>3</sub> :Eu <sup>2+</sup> and YAG:Ce <sup>3+</sup> Dual Phosphora??ina??silicaa??glass
摘要： Phosphors-in-glass (PiG), which serves as a potential bi-replacement of both phosphors and organic encapsulants in high-power white light-emitting diodes (WLEDs), has captured much attention due to its high thermal stability and excellent luminescent properties. However, due to the high temperature-sensitivity and the chemical reactions between phosphors with glass matrix, a variety of phosphors, especially red phosphors could be hardly dispersed into the glass without thermal quenching and decomposition, which greatly limits the improvement of color rendering index and chromaticity tunability of the WLEDs. In this study, adopting the mesoporous silica (FDU-12) and commercial phosphors as raw materials, the phosphors-in-silica-glasses (PiSGs) embedded with red phosphor CaAlSiN3:Eu2+ and yellow phosphor YAG:Ce3+ have been successfully prepared at low sintering temperature (950 ?C) and short preparation time (10 min) using spark plasma sintering. Owing to the well preservation of the originally emissive properties of the embedded phosphors, the warm WLEDs with tunable chromaticity and exhibited a superior performance with LE of 133 lm/W, CCT of 3970 K and CRI of 81 were fabricated by encapsulating the as-prepared PiSGs on the blue chips. Moreover, the PiSG composite exhibits a high thermal conductivity up to 1.6 W/m·K.
关键词： white light-emitting diodes,phosphor in silica glass,tunable chromaticity,mesoporous silica
更新于2025-09-23 15:21:01
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Tunable luminescence and morphological evolution of facile synthesized zinc borate/carbon dots composites for NUV-WLEDs
摘要： A series of zinc borate/carbon dots composites (ZBH/yNCDs) were successfully synthesized under hydrothermal conditions. The influences of yellow N-doped carbon dots (yNCDs) content on the structure, morphologies and luminescence properties of the zinc borate (4ZnO·B2O3·H2O, ZBH) were investigated. With increasing yNCDs content, ZBH in the ZBH/yNCDs composites gradually lost water and eventually became ZB/yNCDs (4ZnO·B2O3, ZB) composites. Meanwhile, the tunable luminescence of ZBH/yNCDs composites and the morphological evolution from rod-like to blocks to sphere-like were achieved by varying the yNCDs content in the zinc borate matrix. The results revealed that the ZBH/yNCDs composite with sphere-like morphology has the strongest white light emission at 395 nm excitation wavelength. Therefore, the ZBH/yNCDs composites may be used as phosphors in the near-ultraviolet (NUV) excitation white-light illumination field. The discovery of this work may also provide new inspirations for solving the self-quenching effect of carbon dots in the solid-state display applications.
关键词： N-doped carbon dots,White light-emitting diodes,Morphology,Zinc borate
更新于2025-09-23 15:21:01