- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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Solution-processed, top-emitting, microcavity polymer light-emitting diodes for the pure red, green, blue and near white emission
摘要： Top-emitting microcavity polymer light-emitting diodes (TMPLEDs) are of great significance for active matrix PLED displays with high color purity. However, the complex device structures of high efficiency microcavity organic light-emitting diodes fabricated by the full vapor deposition technology are not suitable to the solution processed PLEDs. The solution-processed TMPLEDs with simple device structures are promising candidates as the large-area, mass production display techniques. In this work, three strategies were used to apply microcavity into PLEDs: (1) double Ag electrodes performed as the mirrors of cavity, instead of multi-layer Bragg reflector, which simplified the device structure and fabrication process; (2) three solution processed functional layers were specially designed for avoiding the inter-infiltration between the different solution and improve the interface contacts; (3) high order microcavities were utilized according to the optical simulation results, in which thick EMLs benefited to thickness control and reproductivity. As results, the full-color emission including pure red, green, blue was realized, and quasi-white light was also achieved from single polymer emitting material. The achievement of color purity always sacrifices part of current efficiency (CE) due to the spectra narrowing, while the higher CE of green TMPLED (10.08 cd/A) than that of non-cavity PLED (∽8.60 cd/A) cast lights on the future improvement.
关键词： Top-emitting,Interface Engineering,Color Tuning,Polymer Light-Emitting Diodes,Solution-processed,Microcavity
更新于2025-09-16 10:30:52
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[IEEE 2019 26th IEEE International Conference on Electronics, Circuits and Systems (ICECS) - Genoa, Italy (2019.11.27-2019.11.29)] 2019 26th IEEE International Conference on Electronics, Circuits and Systems (ICECS) - Exploiting Negative Impedance Converters to Extend the Bandwidth of LEDs for Visible Light Communication
摘要： This paper proposes, for the ?rst time, an optically lossless light emitting diode (LED) bandwidth extension technique based on the adoption of negative impedance converters applied in the context of high capacity visible light communication systems. The proposed technique aims to achieve bandwidth extension by offsetting the bandwidth-limiting effect of the LED diffusion capacitance through the introduction of a parallel negative capacitance. With the proposed technique, we predict up to 200% improvement in the LED modulation bandwidth with studies based on a veri?ed LED equivalent model.
关键词： negative impedance converters,Light emitting diodes,visible light communication,negative capacitance
更新于2025-09-16 10:30:52
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Pyrene-based hyperbranched porous polymers with doped Ir(piq)2(acac) red emitter for highly efficient white polymer light-emitting diodes
摘要： Here, we designed and prepared a series of hyperbranched porous polymers constructed using fluorene branches and pyrene core, and all hyperbranched porous polymers exhibit intense blue fluorescence, good morphological stability, and high thermal stability. Further, it is found that the aperture sizes for hyperbranched porous polymers can be adjusted by simply changing the content of pyrene and fluorene in the synthesis process. When the feed ratios of pyrene in the total polymers is 15 mol%, the optimized aperture size was obtained, which is slightly larger than the maxlength of complementary red emitter Bis(1-phenylisoquinoline)(acetylacetonate) iridium (III) (Ir(piq)2acac), indicating the Ir(piq)2acac can well distributed in the apertures of hyperbranched porous polymers in co-doped film of Ir(piq)2acac and hyperbranched porous polymers. The fabricated polymer-light-emitting diode (PLED) with such co-doped film as light-emitting layer realizes good white emission with almost equal blue and red emission intensity from hyperbranched porous polymers and Ir(piq)2acac. The balanced electroluminescent (EL) spectra contribute to ideal Commission Internationale de l’Eclairage (CIE) coordinate of (0.326, 0.374) located at white light zone. In addition, the device also achieves high device performance with maximum luminance and current efficiency reaching 5369 cd/m2 and 8.35 cd/A, respectively. We believe that such porous-structure polymers have huge potential applications in the development of highly efficient white PLEDs with reducing production cost.
关键词： White light,Electroluminescence spectra,Polymer light-emitting diodes,Hyperbranched porous polymers
更新于2025-09-16 10:30:52
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Improving the performance of light-emitting diodes via plasmonic-based strategies
摘要： Light-emitting diodes (LEDs), featuring long lifetime, small size, and low energy consumption, are increasingly popular for displays and general light sources. In the past decades, new light-emitting materials and novel device configurations are being continuously investigated to obtain highly efficient LEDs. Nevertheless, the unsatisfying external quantum efficiency severely limits their commercial implementation. Among all the approaches to boost the efficiency of LEDs, the incorporation of plasmonic structures exhibits great potential in increasing the spontaneous emission rates of emitters and improving the light extraction efficiency. In this Perspective, the methods to deal with challenges in quantum-well-based LEDs and organic LEDs by employing plasmonic materials are described, the mechanisms of plasmonic-based strategies to improve the light generation and extraction efficiency are discussed, and the plasmonic control over directional emission of phosphors is introduced as well. Moreover, important issues pertaining to the design, fabrication, and manipulation of plasmonic structures in LEDs to optimize the device performance, as well as the selection roles in finding appropriate plasmonic materials and structures for desired LED devices, are explained. This perspective lists the challenges and opportunities of plasmonic LEDs, with the aim of providing some insights into the future trends of plasmonic LEDs.
关键词： spontaneous emission rates,light-emitting diodes,light extraction efficiency,external quantum efficiency,plasmonic structures
更新于2025-09-16 10:30:52
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High Efficiency Solution-Processed Organic Light-Emitting Diodes with Tetradentate Platinum(II) Emitters
摘要： The realization of high efficiency solution-processed organic light-emitting diodes (OLEDs) by using phosphorescent tetradentate Pt(II) emitters and bipolar organic hosts is demonstrated in this work. To investigate the effect of organic host on the platinum dopant, the performances of solution-processed Pt-OLEDs with various combination between four tetradentate Pt(II) emitters, including two newly developed tetra-Pt-S2 and tetra-Pt-S3, and three bipolar organic hosts m-TPAPy, o-TPAPy, and o-CzPy, have been analyzed and compared. Among the tetradentate Pt(II) complexes studied in this work, tetra-Pt-S3 exhibited the best electroluminescent performance attributable to its bulky molecular scaffold structure, high emission quantum yield, and good solubility in common organic solvents. High external quantum efficiencies (EQEs) of up to 22.4% were achieved in the solution-processed OLED with tetra-Pt-S3 emitter and m-TPAPy host at the dopant concentration of 4 wt%. At a high luminance of 1000 cd m-2, the EQE of this device decreased slightly to 21.0%.
关键词： high efficiency,platinum complexes,organic light-emitting diodes,solution-process,bipolar organic host
更新于2025-09-16 10:30:52
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Derivation and Experimental Verification of the near-field 2D and 3D optical intensities from a finite-size light emitting diode (LED)
摘要： We derive the near-field light intensity distributions of an inorganic LED on its surface and in volumetric space. Our closed-form solution for 3D intensity distribution for a finite-size LED is consistent with Lambert’s Cosine Law, which provides the 3D intensity distribution for an infinitesimal, flat light source. We also derive the formula for the 2D intensity distribution on a diode surface showing its similarity to a Gaussian function, which is typically used to approximate the surface light intensity profile for an LED and a laser diode. Our 2D intensity distribution function produces light propagation similar to the Gaussian beam propagation in space. However, unlike the Gaussian approximation, our formula invariably produces this behavior without assuming the refractive index inside the diode follows a quadratic function of the transverse spatial domains. Our 2D and 3D spatial intensity formulas in near-field for LEDs offer a unique way to calculate the peak intensity that occurs at the center of the flat LED source. We demonstrate, as expected, that the peak intensity increases with the size of the LED source as well as the brightness of each radiative electron-hole pair, which is a function of the drive current and quantum efficiency of the LED.
关键词： Near-field Photometry,Optical Waveguides,Display,Optical Wave Propagation,Closed-Form Solutions,and Lighting.,Lasers,Light Emitting Diodes,Mathematical Physics
更新于2025-09-16 10:30:52
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Lumen Degradation Lifetime Prediction for High Power White LEDs based on the Gamma Process Model
摘要： Nowadays, due to the advancement of design and manufacturing technology, there are many consumer products with high reliability. Similarly, the competition in the business sector influences the product development time to become shorter and that makes it difficult for manufacturers to evaluate the reliability of current products before new products are released to the market. This phenomenon is manifested in the lighting industry, especially for the high power white light-emitting diodes (LEDs) as these products have a long lifetime and high reliability. Currently, the standard to predict the lifetime of LEDs is based on a deterministic nonlinear least squares method which has low prediction accuracy. To overcome this, degradation models are being used to study the reliability of such products, considering the uncertainties and the quality characteristics whose degradation over a period of time can be related to the product lifetime. A stochastic approach based on gamma distributed degradation (GDD) is proposed in this study to estimate the long-term lumen degradation lifetime of phosphor-converted white LEDs. An accelerated thermal degradation test was designed to gather luminous flux degradation data which was analyzed based on maximum likelihood estimation (MLE) and the method of moments (MM) to estimate the parameters for the GDD model. The MLE method has shown superiority over MM in terms of the estimation of the model parameters due to its iterative algorithm being likely to find the optimal estimation. The lifetime prediction results show that the accuracy of the proposed method is much better than the TM-21 nonlinear least squares (NLS) approach which makes it promising for future industrial applications.
关键词： Luminous flux degradation,Gamma distributed degradation (GDD),Method of moments,Light-emitting diodes (LEDs),Maximum likelihood estimation
更新于2025-09-16 10:30:52
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Research on Luminance Distributions of Chip-On-Board Light-Emitting Diodes
摘要： Chip-On-Board Light-Emitting Diodes (COB LED) are increasingly more common. Their development in recent years has directly contributed to increasing the power of LED sources, whilst simultaneously increasing the luminous ?ux from the entire COB. Consequently, it has led to new developments in some applications. Information regarding the size of the light source luminous surface and luminance distribution on its surface is critical for a designer whilst designing optical systems. The purpose of this conducted research was to establish to what extent luminance distribution is even on the examined COB LEDs. In order to verify luminance distributions on an LED surface, direct measurements with a matrix luminance measuring device were made. As a result of the research, it has been observed that luminance distribution is not even, and in many cases luminance maximum does not fall in the geometric center of the luminous surface, which was initially expected. So, it has been concluded that while designing optical systems for COB LEDs, irregular luminance distribution on their surface needs to be considered.
关键词： LED,luminance distribution,COB,lighting technology,Chip-On-Board,COB LED,light-emitting diodes,micro LED
更新于2025-09-16 10:30:52
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Optimization of Hole Injection and Transport Layers for High-Performance Quantum-Dot Light-Emitting Diodes
摘要： High-luminance, e?cient quantum-dot light-emitting diodes (QLEDs) have been achieved by optimizing the balance between the hole injection layer (HIL) and the hole transport layer (HTL). Di?erent concentrations of vanadium oxide (V2O5) and poly[(9,9-dioctyl?uorenyl-2,7-diyl)-co-(4,4’-(4-sec-butylphenyl)diphenylamine)] (TFB) solutions were used to form the e?cient HIL and HTL, respectively, for the QLEDs. The hole injection and transport behavior was characterized by using hole-only devices (HODs). The QLEDs, which were prepared with 0.5 wt.% of V2O5 and 0.1 wt.% of TFB as HIL and HTL, respectively, showed a maximum current e?ciency of 2.27 cd·A?1 and a maximum luminance of 71,260 cd·m?2. Moreover, the turn-on voltage of the device was as low as 2.2 V due to the e?cient carrier injection and transport. The results provide useful information for fabricating high-performance QLEDs.
关键词： Optimization,Hole transport layer,Light-emitting diodes,Quantum-dots,Hole injection layer
更新于2025-09-16 10:30:52
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Effect of a p-type ZnO insertion layer on the external quantum efficiency of GaInN light-emitting diodes
摘要： The external quantum ef?ciency (EQE) of a GaInN green light-emitting diode (LED) is improved by inserting a p-type ZnO layer between the indium tin oxide electrode and the p-type GaN layer. Several hypotheses are discussed to explain the EQE improvement in the LED with the ZnO layer. It is concluded that higher hole injection ef?ciency and better electron con?nement explain the EQE improvement, which is supported by the results of device simulations showing that the EQE is sensitive to the polarization sheet charge density at the interface between the last quantum barrier and electron-blocking layer.
关键词： external quantum efficiency,electron confinement,GaInN,hole injection efficiency,light-emitting diodes,p-type ZnO
更新于2025-09-16 10:30:52