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Improved Reverse Leakage Current in GaInN-based LEDs with a Sputtered AlN Buffer Layer
摘要： In this study, the improvement of reverse leakage current characteristics with a sputtered (SP) -AlN buffer layer in GaInN-based green light-emitting diodes (LEDs) has been presented for the first time. To understand the origin of the improvement, a detailed review and careful analysis of reverse leakage current characteristics were performed. The review and analysis identified that the improvement was primarily caused by the suppression of variable-range-hopping process obtained by replacing conventional low-temperature GaN buffer. Verification that threading dislocations and V- defects can enhance the variable-range-hopping process has been received. We believe that this study will contribute to the realization of green LEDs with advantages of high reliability, a long lifetime, and electrical robustness.
关键词： reverse leakage current,dot-like local emission,light-emitting diodes,Frenkel-Poole emission,variable-range-hopping
更新于2025-09-11 14:15:04
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Sub-millisecond Control of Neuronal Firing by Organic Light-Emitting Diodes
摘要： Optogenetics combines optics and genetics to enable minimally invasive cell-type-specific stimulation in living tissue. For the purposes of bio-implantation, there is a need to develop soft, flexible, transparent and highly biocompatible light sources. Organic semiconducting materials have key advantages over their inorganic counterparts, including low Young’s moduli, high strain resistances, and wide color tunability. However, until now it has been unclear whether organic light emitting diodes (OLEDs) are capable of providing sufficient optical power for successful neuronal stimulation, while still remaining within a biologically acceptable temperature range. Here we investigate the use of blue polyfluorene- and orange poly(p-phenylenevinylene)-based OLEDs as stimuli for blue-light-activated Sustained Step Function Opsin (SFFO) and red-light-activated ChrimsonR opsin, respectively. We show that, when biased using high frequency (multi-kHz) drive schemes, the OLEDs permit safe and controlled photostimulation of opsin-expressing neurons and were able to control neuronal firing with high temporal-resolution at operating temperatures lower than previously demonstrated.
关键词： neurons,photoexcitation,electrophysiology,pulsed-operation,bioelectronics,organic light-emitting diodes,optical stimulation,optogenetics
更新于2025-09-11 14:15:04
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Best practices for measuring emerging light-emitting diode technologies
摘要： The arrival of light-emitting diodes based on new materials is posing challenges for the characterization and comparison of devices in a trusted and consistent manner. Here we provide some advice and guidelines that we hope will benefit the community.
关键词： LED characterization,emerging technologies,performance metrics,standardization,light-emitting diodes
更新于2025-09-11 14:15:04
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Designing High‐Performance LED Phosphors by Controlling the Phase Stability via a Heterovalent Substitution Strategy
摘要： Phosphor-converted white light-emitting diodes (LEDs) are currently playing key roles in the lighting and display industries and trigger urgent demands for the discovery of “good” phosphors with high quantum efficiency, improved thermal stability, and controllable excitation/emission properties. Herein, a general and efficient heterovalent substitution strategy is demonstrated in K2HfSi3O9:Eu2+ achieved by Ln3+ (Ln = Gd, Tb, Dy, Tm, Yb, and Lu) doping to optimize luminescence properties, and as an example, the Lu3+ substitution leads to improvement of emission intensity and thermal stability, as well as tunable emission color from blue to cyan. The structural stability and Eu2+ occupation via Lu3+ doping have been revealed by the structural elaboration and density functional theory calculations, respectively. It is shown that heterovalent substitution allows predictive control of site preference of luminescent centers and therefore provides a new method to optimize the solid-state phosphors for LEDs.
关键词： phosphors,photoluminescence,white light-emitting diodes
更新于2025-09-11 14:15:04
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[IEEE 2018 10th International Conference on Advanced Infocomm Technology (ICAIT) - Stockholm, Sweden (2018.8.12-2018.8.15)] 2018 10th International Conference on Advanced Infocomm Technology (ICAIT) - Exploring Evolution of Patent Litigation and Licensing Strategy: The Case of Philips's Light Emitting Diodes (LED) Patents
摘要： LED lighting has received considerable attention due to high energy efficiency, high intensity of brightness, high reliability, low radiated heat, long life span and negligible UV rays. As time goes by, some powerful and invincible patents which had been used as litigation weapons by patent giants are expired. These patent giants changed their strategies to revamp their businesses by earning licensing revenue or releasing some of their patents. This study conducts patent litigation and IP competitiveness analysis to explore Philips’s patent portfolio, identify prospective and valuable litigated patents, and illustrate its litigation /licensing strategy. Visualizations of overall research results and IP implications can benefit policy maker, LED leaders and followers such as China, Taiwan and Korea-based companies in the post oligopoly era.
关键词： patent licensing,patent litigation,patent competitiveness,Light Emitting Diodes (LED)
更新于2025-09-11 14:15:04
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Response of Mustard Microgreens to Different Wavelengths and Durations of UV-A LEDs
摘要： Ultraviolet A (UV-A) light-emitting diodes (LEDs) could serve as an effective tool for improving the content of health-promoting bioactive compounds in plants in controlled-environment agriculture (CEA) systems. The goal of this study was to investigate the effects of UV-A LEDs at different wavelengths (366, 390, and 402 nm) and durations (10 and 16 h) on the growth and phytochemical contents of mustard microgreens (Brassica juncea L. cv. “Red Lion”), when used as supplemental light to the main LED lighting system (with peak wavelengths of 447, 638, 665, and 731 nm). Plants were grown for 10 days under a total photon flux density (TPFD) of 300 μmol m?2 s?1 and 16-h light/8-h dark period. Different UV-A wavelengths and irradiance durations had varied effects on mustard microgreens. Supplemental UV-A radiation did not affect biomass accumulation; however, the longest UV-A wavelength (402 nm) increased the leaf area of mustard microgreens, regardless of the duration of irradiance. The concentration of the total phenolic content and α-tocopherol mostly increased under 402-nm UV-A, while that of nitrates increased under 366- and 390-nm UV-A at both radiance durations. The contents of lutein/zeaxanthin and β-carotene increased in response to the shortest UV-A wavelength (366 nm) at 10-h irradiance as well as longer UV-A wavelength (390 nm) at 16 h irradiance. The most positive effect on the accumulation of mineral elements, except iron, was observed under longer UV-A wavelengths at 16-h irradiance. Overall, these results suggest that properly composed UV-A LED parameters in LED lighting systems could improve the nutritional quality of mustard microgreens, without causing any adverse effects on plant growth.
关键词： mustard microgreens,mineral elements,UV-A,antioxidants,light-emitting diodes,growth
更新于2025-09-11 14:15:04
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Nanostructured colloidal quantum dots for efficient electroluminescence devices
摘要： The exceptional quality of light generated from colloidal quantum dots has attracted continued interest from the display and lighting industry, leading to the development of commercial quantum dot displays based on the photoluminescence down-conversion process. Beyond this technical level, quantum dots are being introduced as emissive materials in electroluminescence devices (or quantum dot-based light-emitting diodes), which boast high internal quantum efficiency of up to 100%, energy efficiency, thinness, and flexibility. In this review, we revisit various milestone studies regarding the core/shell heterostructures of colloidal quantum dots from the viewpoint of electroluminescence materials. Development of nanostructured colloidal quantum dots advanced from core/shell heterostructure, core/thick shell formulation, and delicate control of confinement potential shape has demonstrated close correlation of the photophysical properties of quantum dots with the performance of electroluminescence device, which provided useful guidelines on the heterostructured quantum dots for mitigating or eliminating efficiency limiting phenomena in quantum dot light emitting diodes. To enable practical and high performance quantum dot-based electroluminescence devices in the future, integration of design concepts on the heterostructures with environmentally benign systems will be crucial.
关键词： Electroluminescence,Nanocrystals,Colloidal Quantum Dots,Core/Shell Heterostructures,Light Emitting Diodes
更新于2025-09-11 14:15:04
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[IEEE 2019 IEEE Photonics Conference (IPC) - San Antonio, TX, USA (2019.9.29-2019.10.3)] 2019 IEEE Photonics Conference (IPC) - High Performance Ultraviolet Micro-LED Arrays for Fine-Pitch Micro Displays
摘要： Highly efficient ultraviolet micro LED arrays are demonstrated. Small devices (5 microns in size) suitable for high resolution (725 ppi) can be produced with low leakage current and good emission spectra stability. A 10 by 10 array is achieved with passive-matrix driving connection.
关键词： passive matrix driving circuitry,micro-display,micron scale light emitting diodes,ultraviolet emission
更新于2025-09-11 14:15:04
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Effects of interfaces and current spreading on the thermal transport of micro-LEDs for kA-per-square-cm current injection levels
摘要： The three-dimensional thermal characteristics of micro-light-emitting diodes (mLEDs) on GaN and sapphire substrates were studied with forward-voltage methods, thermal transient measurements, and infrared imaging. The mLEDs on the GaN substrate showed an approximately 10 °C lower junction temperature and smaller amplitude of the K factors than those on the sapphire substrate under the current injection level of 4 kA cm?2. The thermal transient measurement showed that the spreading thermal resistances of the mesa, the GaN epilayer, and the interface of the GaN/substrate were reduced significantly for mLEDs on the GaN substrate because of the high-quality GaN crystal and the interfaces. The infrared thermal images showed lower total average junction temperatures and more uniform temperature distributions for the mLEDs on the GaN substrate, which were also simulated with APSYS software. The thermal transport mechanisms are discussed for the lateral and vertical directions in the mLEDs.
关键词： sapphire substrate,micro-light-emitting diodes,GaN substrate,junction temperature,thermal transport,infrared imaging,APSYS simulation
更新于2025-09-11 14:15:04
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Nanoplatelet modulation in 2D/3D perovskite targeting efficient light-emitting diodes
摘要： Light-emitting diodes (LEDs) based on two-dimensional (2D) perovskite nanoplatelets exhibit high electroluminescence (EL) efficiency because of the quantum confinement effect, which increases electron–hole recombination to promote radiative emission. It is well-known that a 2D nanoplatelet structure (?n? = 1) is detrimental for luminescence efficiency due to possible thermal quenching of excitons at room temperature. Here, a simple strategy is developed to suppress growth of NMA2PbBr4 (?n? = 1) nanoplatelets by carefully tuning the precursor ratio of cesium bromide (CsBr), formamidinium bromide (FABr) and 1-naphthylmethylammonium bromide (NMABr). The sub-domain size of the perovskite crystal decreases as the long-chain ligand NMABr ratio increases, leading to enhanced photoluminescence quantum yields (PLQY) due to size confinement effect when the NMABr ratio is below 60%. Unfortunately, the NMA2PbBr4 component in 2D/3D perovskites also grows with increasing NMABr ratio, which results in poor EL efficiency. FABr incorporation can provide additional control over suppression of NMA2PbBr4 growth in 2D/3D perovskites. A compact and uniform perovskite film with reduced NMA2PbBr4 content achieves PLQY of ～61%. Benefiting from these features, a green perovskite LED yields current efficiency of 46.8 cd A?1 with an external quantum efficiency of 14.9%. This study paves a new way to modulate the crystal structure in perovskites via a simple and effective method for high-performance LEDs.
关键词： light-emitting diodes,perovskite,quantum confinement,electroluminescence,nanoplatelets
更新于2025-09-11 14:15:04