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Rational Design of Axially Chiral Platinabinaphthalenes with Aggregation-Induced Emission for Red Circularly Polarized Phosphorescent Organic Light-Emitting Diodes
摘要： Circly polarized luminescent (CPL) materials have received great interest due to their potential applications in next-generation displays. However, the development of easily accessible red circularly polarized phosphorescent emitters for practical organic light-emitting diodes fabrication remains a grand challenge. In this paper, we report a new family of CPL-active platinum complexes based on the binaphthalene chiral platform. These axially chiral platinabinaphthalenes were facile synthesized by directly incorporating platinum(II) into the π-conjugated backbone of commercially available enantiopure binaphthalene derivate. These complexes exhibit aggregation-induced circularly polarized phosphorescence enhancement with high quantum yields up to 66% and luminescence dissymmetry factors around 2.6×10?3. Moreover, solution-processable circularly polarized organic light-emitting diodes (CPOLEDs) using these complexes as emitters show good performance with the maximum luminance up to 3500 cd m2 and dissymmetry factor values around 1.0×10?3. These findings by rational design of axially chiral platinabinaphthalenes are important for the development of high-performance CPL complexes for CPOLEDs.
关键词： circularly polarized luminescence,binaphthalene,organic light-emitting diode,platinum complex,aggregation-induced emission
更新于2025-09-16 10:30:52
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Highly Efficient Solution-Processed TADF Bluish-Green and Hybrid White Organic Light-Emitting Diodes Using Novel Bipolar Host Materials
摘要： Two pyridine containing bipolar host materials with high triplet energy, 9,10-dihydro-9,9-dimethyl-10-(3-(6-(3-(9,9-dimethylacridin-10(9H)-yl)phenyl)pyridin-2-yl)phenyl acridin (DDMACPy) and N-(3-(6-(3-(diphenylamino)phenyl)pyridin-2-yl)phenyl)-N-phenylbenzenamine (DTPAPy), are synthesized from modifying the commonly adapted host material 2,6-bis(3-(9H-carbazol-9-yl)phenyl)pyridine (DCzPPy). The HOMO levels of DDMACPy (5.50 eV) and DTPAPy (5.60 eV) are found to be shallower than that of DCzPPy (5.90 eV) that leads to the improvement in hole injection from the hole transport layer PEDOT:PSS (WF = 5.10 eV). These host materials are used in the emitting layer of bluish-green organic light-emitting diode (OLED) with the TADF emitter, 9,9-dimethyl-9,10-dihydroacridine-2,4,6-triphenyl-1,3,5-triazine (DAMC-TRZ), as the guest. The DDMACPy-based device shows the highest performance among them with the maximum external quantum efficiency (EQEmax), current efficiency (CEmax) and power efficiency (PEmax) of 21.0%, 53.1 cd A-1 and 44.0 lm w-1 at CIE (0.17, 0.42), respectively. By further doping with the red emitting phosphor iridium(III) bis(2-phenylquinoline)(2,2,6,6-tetramethylheptane-3,5-ionate) [Ir(dpm)PQ2] and yellow emitting phosphor iridium(III) bis(4-(4-t-butyphenyl) thieno[3,2-c]pyridinato-N,C20)acetylacetonate (PO-01-TB) emitters into the bluish-green emitting layer, a TADF-phosphor hybrid white OLED (T-P WOLED) is obtained with excellent EQEmax, CEmax and PEmax of 17.4%, 48.7 cd A-1 and 44.5 lm w-1 at CIE (0.35, 0.44), respectively. Moreover, both the bluish-green and white OLED show the low efficiency roll-off with external quantum efficiencies at the brightness of 1000 cd m-2 (EQE1000) 18.7% and 16.2% respectively, and are the highest performance records among the solution-processed TADF bluish-green and T-P WOLEDs.
关键词： low efficiency roll-off,solution process,bipolar host material,TADF bluish-green organic light-emitting diode,hybrid white organic light emitting diode
更新于2025-09-12 10:27:22
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What limits the efficiency of GaN-based superluminescent light-emitting diodes (SLEDs)?
摘要： Gallium-nitride-based SLEDs are attractive light sources for augmented reality displays and other applications. However, the electrical-to-optical power conversion efficiency (PCE) of SLEDs is still far below the record-high values reported for LEDs. Utilizing advanced numerical device simulation, this paper investigates the internal physical pro- cesses that cause the low PCE of SLEDs. The poor hole conductivity strongly reduces the electrical efficiency, similar to laser diodes. However, in contrast to laser diodes, the rising carrier density in the active layers is identified as main reason for enhanced Auger recom- bination that severely limits the internal quantum efficiency. Design improvement options are demonstrated.
关键词： Superluminescent light-emitting diode,Auger recombination,InGaN/GaN,Laser diode,Self-heating,Power conversion efficiency,SLED,Hole conductivity
更新于2025-09-12 10:27:22
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Closing the Cyan-Gap toward Full Spectrum LED Lighting with NaMgBO3:Ce3+
摘要： The photoluminescence spectrum generated by an ordinary phosphor-converted white light-emitting diode (pc-wLED) that combines a blue LED chip with a yellow phosphor or a near-UV LED with red, green and blue phosphors contains a notable cavity in the cyan region of the visible spectrum (480-520 nm) that reduces the color quality produced by these lights. Here, we report a new bright blue-cyan-emitting phosphor, NaMgBO3:Ce3+, that bridges the gap. Rietveld refinements verify the rare-earth substitution while ab initio calculations prove Ce3+ occupies the Na+ sites. NaMgBO3:Ce3+ is excited by a broad range of near-UV light sources and produces a blue-cyan emission with a high (internal) quantum efficiency, minimal thermal degradation, and zero-chromaticity drift at elevated temperatures. Fabricating a near-UV (λex = 370 nm) pumped pc-wLED using NaMgBO3:Ce3+ along with commercially available phosphors demonstrates a well-distributed warm white light with a high color-rendering index (Ra) of 91 and a low correlated color temperature (CCT) of 3645 K. Closing the cyan cavity with NaMgBO3:Ce3+ is ideal for generating a pleasant, full-spectrum, warm white light.
关键词： full-spectrum LED lighting,NaMgBO3:Ce3+,blue-cyan-emitting phosphor,color-rendering index,phosphor-converted white light-emitting diode
更新于2025-09-12 10:27:22
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[IEEE 2019 IEEE Industry Applications Society Annual Meeting - Baltimore, MD, USA (2019.9.29-2019.10.3)] 2019 IEEE Industry Applications Society Annual Meeting - Evaluation of Bit Error Ratio in Differential Phase-Shift-Keying Modulation Applied to VLC LED Drivers
摘要： This work presents a binary differential phase-shift keying (DPSK) modulation technique for visible light communication (VLC) systems aimed at low to moderate data rate applications. VLC uses the modulated light of LEDs to transmit data wireless. Such feature is added into artificial lighting systems by controlling the light intensity of a source. However, in most cases, modulation capabilities for VLC are employed with the addition of extra power components, which may harm efficiency and cost standards. Therefore, single switch LED drivers are preferable to provide VLC along with average current regulation. They are standard low-cost solutions that are able to perform both functions providing a satisfactory efficiency. Hence, in this work, DPSK modulation is applied to a buck converter operating in continuous conduction mode at 250 kHz, providing a raw data rate of 125 kbps. DPSK is advantageous because it overcomes possible parameters changes at the converter, along with possible duty cycle changes given by the control system of the average current for lighting. Moreover, the system performance is evaluated by means of its bit error ratio (BER) over signal-to-noise ratio (SNR), in a line-of-sight setup with variable distances between transmitter and receiver, showing a good behaviour of a BER less than 10?3 for about 8.1 m in a 8.4 W LED load.
关键词： Switched Converter,Solid-State Lighting,Light Emitting Diode,Visible Light Communication
更新于2025-09-12 10:27:22
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[IEEE 2019 Second Balkan Junior Conference on Lighting (Balkan Light Junior) - Plovdiv, Bulgaria (2019.9.19-2019.9.21)] 2019 Second Balkan Junior Conference on Lighting (Balkan Light Junior) - LED Luminaire Optical Lens Optimization for Road Lighting Designed According to Luminance Requirement
摘要： A methodology for iterative optimization of optical systems for street LED luminaires intended for roads designed according to luminance requirement is proposed in the paper. The methodology comprises the following stages: iterative change of the shape of secondary lens of a computer model of the optical system, photometric analysis using the Monte Carlo raytracing method of the modelled three- dimensional optical systems to calculate their photometric characteristics, optimal road lighting calculations with an optimum criterion – maximum luminaire spacing meeting the requirements of standard for the selected M6 lighting class of the road, through the analysis of which the optimal solution is found.
关键词： light-emitting diode,light distribution,optical lens,Monte Carlo raytracing,road lighting,optimization
更新于2025-09-12 10:27:22
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Optimizing clinical images with a smartphone and light-emitting diode
摘要： High-quality images are important for documentation, education and communication in dermatology. In tele-dermatology and artificial intelligence-based skin diagnostic system, the quality of images is crucial for accurate diagnosis. While various camera types are suitable for different clinical applications, smartphone cameras are improving dramatically and becoming more popular. As the resolution of the camera itself has improved, the quality of the light source has become the most important determinant of quality and consistent lighting is extremely important for before-and-after comparisons. Use of the built-in flash may lead to overexposure, intense surface reflections, blurring caused by failing of autofocus in the dark, and subtle changes during synchronization. Light-emitting diodes (LED) are now widely used by professional photographers and videographers and the images obtained with the LED light may be more reproducible than flash-assisted photographs. We evaluated the use of an LED pad (CN-luxpad23, Nanguan, China) for medical photography using different models of smartphones (iphone 7plus (Apple Inc., USA), iphone 6 plus (Apple Inc., USA), and HUAWEI mate10 pro (HUAWEI Inc., China)) in flash off mode, LED light intensity 40, color temperature 5600K (Figure 1). The technique was evaluated in 75 different lesions of 61 patients on the scalp, face, neck, trunk, extremities, palms and soles, intertriginous areas, genital and perianal areas, auricle and oral cavity in varying conditions of room light intensity. Three photos were taken for each lesion, using smartphone without built-in flashlight, with built-in flashlight and with “LED pad technique” respectively. The “LED pad technique” produced superior results in 90.67% (68/75) of the cases compared to using smartphone with or without built-in flash light regardless of ambient light (Figure 2). The remaining cases 9.33% (7/75) were on the scalp or face with too much reflection from sebum or whole body photographing needing a stronger light source. Advantages include low cost, ease of use and consistency of results for follow-up comparisons. Moreover, any LED panel with sufficient light intensity and a color temperature 5600K could be used in this way. The major limitation was lower intensity when the battery reaches a critical low level. Besides, a device to allow the LED panel and camera to be attached and allow two hands to hold the entire smartphone and shoot would be a valuable addition.
关键词： light-emitting diode,smartphone,light,LED,Clinical photography
更新于2025-09-12 10:27:22
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Blue LED light irradiation enhances L-ascorbic acid content while reducing reactive oxygen species accumulation in Chinese cabbage seedlings
摘要： Chinese cabbage is one of the most representative vegetables in Southeast Asia and a main source of L-Ascorbic acid (AsA) for the human diet. In this study, we applied di?erent light qualities (red, blue and white) supported by light-emitting diode (LED) device to enhance AsA content in Chinese cabbage (Brassica rapa ssp. pekinensis) seedlings. Based on our results, blue LED light irradiation with an intensity of 125 μmol m?2s?1 increased the AsA content of ?ve-day-grown Chinese cabbage seedlings by 40% compared with white LED light irradiation. Accordingly, blue LED light irradiation induced expression of the AsA biosynthetic- and recycling-related genes. Interestingly, the reactive oxygen species (ROS) content of Chinese cabbage seedlings was decreased by blue LED light irradiation. In addition, the technology improving AsA content by blue LED light irradiation was applicable to other edible vegetable sprouts as well as to Chinese cabbage sprouts. Conclusively, our report introduces a source technology for arti?cially improving the AsA content of Chinese cabbage seedlings by applying blue LED light, which implies that application of certain types of LED light enables on-purpose cultivation of crops.
关键词： Chinese cabbage,Blue light,Ascorbic acid (AsA),Light-emitting diode (LED),Antioxidant
更新于2025-09-12 10:27:22
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Arduino Based Traffic Light System With Integrated LED Advertising Display
摘要： Rapid advancement in scientific knowledge and growth in worldwide economic activities has led to a steep rise in the volume of vehicular activity for human and product mobility controls hence in addition to controllers are, therefore, a critical necessity of the modern – day society. Toward this end, this paper is aimed toward the design of microcontroller-based traffic control device taking as a case study the complex layout and linkage among the service roads of the Senate building and College of Science and Technology, Covenant University, Nigeria. The Arduino platform is the microcontroller preference for this idea. Also, to make this idea more effective and productive, a Light Emitting Diode (LED) advertising displays has been incorporated into its implementation to take advantage of the red light wait time to disseminate useful information or facts.
关键词： Microcontroller,Arduino,Traffic Light Control System,LED Advertising Displays,LED (Light Emitting Diode)
更新于2025-09-12 10:27:22
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A DOUBLE-MASKED, RANDOMIZED, SHAM-CONTROLLED, SINGLE-CENTER STUDY WITH PHOTOBIOMODULATION FOR THE TREATMENT OF DRY AGE-RELATED MACULAR DEGENERATION
摘要： The LIGHTSITE I study investigated the efficacy and safety of photobiomodulation (PBM) treatment in subjects with dry age-related macular degeneration. Thirty subjects (46 eyes) were treated with the Valeda Light Delivery System, wherein subjects underwent two series of treatments (3· per week for 3–4 weeks) over 1 year. Outcome measures included best-corrected visual acuity, contrast sensitivity, microperimetry, central drusen volume and drusen thickness, and quality of life assessments. Photobiomodulation-treated subjects showed a best-corrected visual acuity mean letter score gain of 4 letters immediately after each treatment series at Month 1 (M1) and Month 7 (M7). Approximately 50% of PBM-treated subjects showed improvement of $5 letters versus 13.6% in sham-treated subjects at M1. High responding subjects ($5-letter improvement) in the PBM-treated group showed a gain of 8 letters after initial treatment (P , 0.01) and exhibited earlier stages of age-related macular degeneration disease. Statistically significant improvements in contrast sensitivity, central drusen volume, central drusen thickness, and quality of life were observed (P , 0.05). No device-related adverse events were reported. Photobiomodulation treatment statistically improved clinical and anatomical outcomes with more robust benefits observed in subjects with earlier stages of dry age-related macular degeneration. Repeated PBM treatments are necessary to maintain benefits. These pilot findings support previous reports and suggest the utility of PBM as a safe and effective therapy in subjects with dry age-related macular degeneration.
关键词： contrast sensitivity,best-corrected visual acuity,light-emitting diode,vision loss,low-level light therapy,mitochondria,photobiomodulation,dry age-related macular degeneration,drusen
更新于2025-09-12 10:27:22