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Organic Upconversion Display with an over 100% Photon-to-photon Upconversion Efficiency and a Simple Pixelless Device Structure
摘要： Comparing to traditional near infrared (NIR) imaging devices, NIR-to-visible upconversion display which integrated a NIR photodetector with a visible light-emitting diode have merits of simple device structure, low cost, high resolution, and a simple pixelless structure. However, photon-to-photon upconversion efficiencies of these devices are typically much lower than unity. Here we report an all-organic NIR-to-visible upconversion display with a photon-to-photon upconversion efficiency higher than 100% by integrating a photomultiplying organic NIR photodetector with a high-efficiency thermally activated delayed fluorescent organic light-emitting-diode. To the best of our knowledge, this is the first report showing a photon-to-photon upconversion efficiency over 100% without using a built-in transistor for current amplification.
关键词： organic photodetector,NIR-to-visible upconversion,photon-to-photon efficiency,thermally activated delayed fluorescence,organic light-emitting diode
更新于2025-09-23 15:21:01
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Optical properties of metamorphic type-I InAs <sub/> 1? <i>x</i> </sub> Sb <sub/><i>x</i> </sub> /Al <sub/><i>y</i> ? </sub> In <sub/> 1? <i>y</i> ? </sub> As quantum wells grown on GaAs for the mid-infrared spectral range
摘要： We analyse the optical properties of InAs1?xSbx/Aly In1?y As quantum wells (QWs) grown by molecular beam epitaxy on relaxed Aly In1?y As metamorphic buffer layers (MBLs) using GaAs substrates. The use of Aly In1?y As MBLs allows for the growth of QWs having large type-I band offsets, and emission wavelengths >3 μm. Photoluminescence (PL) measurements for QWs having Sb compositions up to x = 10% demonstrate strong room temperature PL up to 3.4 μm, as well as enhancement of the PL intensity with increasing wavelength. To quantify the trends in the measured PL we calculate the QW spontaneous emission (SE), using a theoretical model based on an eight-band k·p Hamiltonian. The theoretical calculations, which are in good agreement with experiment, identify that the observed enhancement in PL intensity with increasing wavelength is associated with the impact of compressive strain on the QW valence band structure, which reduces the band edge density of states making more carriers available to undergo radiative recombination at fixed carrier density. Our results highlight the potential of type-I InAs1?xSbx/Aly In1?y As metamorphic QWs to address several limitations associated with existing heterostructures operating in the mid-infrared, establishing these novel heterostructures as a suitable platform for the development of light-emitting diodes and diode lasers.
关键词： light-emitting diode,k·p modelling,metamorphic heterostructure,mid-infrared,semiconductors,molecular beam epitaxy,photonics
更新于2025-09-23 15:19:57
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Effect of Light-Emitting Diode Irradiation on Chronic Nonhealed Wound After Below-Knee Amputation
摘要： Chronic nonhealed wound after below-knee amputation is a serious problem that is faced by the health care team; therefore, there is a need to find an adjuvant therapy to address this problem. The aim of the study is to evaluate the therapeutic efficacy of light-emitting diode (LED) irradiation on chronic nonhealed wound after below-knee amputation using a digitalized method of evaluation by Adobe Photoshop CS5 aided by magnetic lasso tool. Thirty patients with chronic nonhealed wound (≥4 weeks) after below-knee amputation were randomly divided into 2 equal groups, with 15 participants in each. Group A received the LED irradiation for 24 sessions (3 sessions per week) in addition to the standard medical treatment, and the second experimental group (group B) received the standard medical treatment for 8 weeks. Methods of evaluation included the wound surface area: for tracing the wound perimeter using a computerized software. Results showed that both LED irradiation therapy and standard medical treatment were effective in healing the chronic nonhealed wound, but the LED was more effective than standard medical treatment alone. A clear improvement in the results of wound healing surface area was found in group A, with an improvement percentage of 50.63%, when compared with group B, which used the standard medical treatment alone, with an improvement percentage of 43.96%.
关键词： wound surface area measurement,below-knee amputation,chronic nonhealed wound,light-emitting diode irradiation
更新于2025-09-23 15:19:57
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Closed Loop Control of a Series Class-E Voltage-Clamped Resonant Converter for LED Supply with Dimming Capability
摘要： In this work, a new closed-loop control system is applied to a class-E resonant DC–DC converter with voltage clamp used for light-emitting diode (LED) supply. The proposed power topology was first described by Ribas et al. in a recent work. In the present paper, the LED current is sensed and used to implement a feedback control loop instead of the simplified feedforward scheme used in this previous reference. To design the control, a novel, simplified small-signal model is presented. This model is used to analyze the converter behavior as a function of the output power. The proposed approximation is significantly simpler than the multifrequency averaging technique normally used to analyze resonant converters. The feedback control loop is designed to reduce the LED low frequency current ripple while providing dimming control. Both the model and the control are verified by simulation and laboratory experimentation and the results obtained are in good accordance with the expected values.
关键词： small-signal dynamic model,light-emitting diode (LED) driver,high efficiency LEDs,resonant DC–DC converter,Class-E inverter,single-switch topology,closed-loop control,voltage clamp
更新于2025-09-23 15:19:57
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Emission spectrum control in monolithic blue-cyan dichromatic light-emitting diodes
摘要： InGaN-based dichromatic light emitting diodes (LEDs) emitting in the blue and cyan spectral ranges simultaneously, are investigated both experimentally and theoretically. Two main approaches to controlling the ratio of blue-to-cyan components in the emission spectrum are suggested and analyzed: (i) thickness variation of the GaN barrier between the blue and cyan quantum wells and (ii) optimization of the barrier doping with n- or p-type impurities. Detailed examination of the approaches is carried out in order to understand their capabilities for intentional variation of the blue-to-cyan ratio in a wide range. Based on numerical simulations, a novel mechanism, invoking enhanced Shockley-Read-Hall recombination in the barrier and underlying both approaches, is suggested and discussed. It is shown that proposed design of the monolithic blue-cyan LEDs does not result in substantial decrease of the LED emission efficiency compared to monochromatic blue or cyan reference samples.
关键词： InGaN,simulation,quantum well,doping,emission spectrum,light-emitting diode
更新于2025-09-23 15:19:57
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Recent progress in phosphorescent Ir(III) complexes for nondoped organic light-emitting diodes
摘要： Highly efficient phosphorescent organic light-emitting diodes (PHOLEDs) with simple configuration as well as low cost fabrication process have attracted much interest for both academic researches and commercial endeavors. This review provides an update on recent advances in the development Ir(III) complexes and their applications in nondoped PHOLEDs fabricated by both vacuum deposition and solution-processed approaches. The modification of chemical structures of the small molecular Ir(III) complexes and dendrimers through incorporating multiple functional moieties could effectively adjust the optical and electronic characters. These complexes typically possess reduced intermolecular aggregation, various hole and electron transporting abilities so that high-performance nondoped PHOLEDs can be developed. The corresponding structural, optical, electronic, photophysical as well as the EL properties in different colors over the whole spectral region are surveyed and highlighted. In the end, the perspectives of the development for the further trend are presented, hopefully to provide useful guidance for the research on highly efficient Ir(III) complexes and corresponding nondoped PHOLEDs.
关键词： Organic light-emitting diode,Ir(III) complex,Nondoped devices,Phosphorescence
更新于2025-09-23 15:19:57
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Illuminating homes with LEDs in India: Rapid market creation towards low-carbon technology transition in a developing country
摘要： Near-term climate change mitigation calls for technological innovation and widespread implementation of appropriate technologies. This is salient in emerging economies, where impending socio-economic and infrastructural transitions hold immense potential for locking-in low-carbon development pathways. Yet, little is understood about how developing countries can scale appropriate technology transitions, given their often underdeveloped technological innovation capabilities and supporting infrastructures and finances. This paper examines a recent, rapid, and ongoing transition of India's lighting market to light emitting diode (LED) technology, from a negligible market share to LEDs becoming the dominant lighting products within five years, despite the country's otherwise limited visibility in the global solid-state lighting industry. Annual sales of LED bulbs grew more than 130 times to over 650 million bulbs between 2014–2018, with over 30 billion kWh of estimated annual energy savings. Focusing on this striking story of technology transition, this paper analyzes India's LED uptake using semi-structured interviews and drawing on the technology innovation systems literature. The results show that the success of transition coexists with its share of shortfalls, and that there is an important tension between the lowering of upfront costs of low-carbon technologies and the efforts to enhance domestic technological capabilities. The paper discusses the results for the Indian LED case and emphasizes the importance of consistent strategic action taking into account all (and not limited) parts of the technology innovation system, while also providing insights on how mitigation technologies can be developed and deployed in developing countries.
关键词： Technology innovation systems,Light emitting diode (LED),Developing countries,India,Solid state lighting,Climate change mitigation,Energy efficiency
更新于2025-09-23 15:19:57
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Dual-band light-emitting diode based on microwheel cavity
摘要： Compact and broadband electroluminescent (EL) devices have garnered considerable interest in recent years. In this study, we have fabricated a light-emitting diode (LED) based on a GaN microwheel cavity with a peak emission wavelength of 438 nm. Another emission peak at 512 nm is realized by coating CH3NH3PbBr3 on the LED. The microwheel-cavity–based LED is fabricated by photolithography and inductively coupled plasma etching process. The opto-electrical performance of the device is characterized in terms of the EL spectrum, luminescence intensity, full width at half maximum, and 3 dB bandwidth. Compared to the device without the CH3NH3PbBr3 layer, the proposed device exhibits dual-band illumination and higher 3 dB bandwidth with potential applications in optical communication.
关键词： CH3NH3PbBr3,dual-band illumination,GaN,microwheel cavity,light-emitting diode
更新于2025-09-23 15:19:57
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Optimization and scale-up of an LED-illuminated microalgal photobioreactor for wastewater treatment
摘要： The use of LED-illuminated photobioreactors with microalgae has been extensively studied for wastewater treatment. Most studies have used isolated microalgae species; however, this practice does not match the reality of conditions in wastewater treatment plants. Operational conditions that promote greater growth of algal biomass and that remove pollutants most effectively are disputed in the literature. In this context, LED–illuminated photobioreactors with microalgae were evaluated using multivariate analysis in order to optimize removal of pollutants (nitrogen, phosphorus, and carbonaceous organic matter). Three variables were evaluated: operating time, LED wavelength, and luminous ?ux intensity. A microalgae consortium was used in the photobioreactor. In addition to the LED-illuminated photobioreactors, control photobioreactors illuminated by sunlight were also operated. Using the results obtained in the optimization, a scaled-up reactor approximately 8.5 times larger in volume was operated to evaluate if the behavior would be maintained. The best operational conditions for the removal of pollutants were observed in LED-illuminated photobioreactors operated under a light intensity of 700 μmol·m?2s?1 for 15 days. Under these conditions, it was possible to remove 89.97% of carbonaceous organic matter, 86.50% of nitrogen, and 30.64% of phosphorus. The scaled-up photobioreactor operated with similar performance.
关键词： multivariate optimization,Light-emitting diode,microalgae,scale-up,removal of pollutants
更新于2025-09-23 15:19:57
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Multiwell plates for obtaining a rapid microbial dose-response curve in UV-LED systems
摘要： UV light-emitting diodes (UV-LEDs) have emerged as a new technology for water disinfection. Multiwell plates are a common tool in biological research, but they have never been used for UVC/UVB-inactivation experiments of microorganisms. In this study, a novel, rapid and simple UVC/UVB-inactivation assay was developed for a UV-LED system using a multiwell plate setup (96- and 24-well plates). The relative incident irradiance distribution across the exposed area was examined by spectroradiometry and nitrate-nitrite uniformity assay. The two methods showed a good correlation and high distribution factors (> 0.89 and > 0.94 for 96- and 24-well plates, respectively). In addition, the potential of the new system for determining disinfection efficacy of E. coli and MS2 coliphage by UV-LEDs emitting at central wavelengths of 265 nm and 285 nm was demonstrated. The inactivation rate constants were comparable to those obtained using UV-LED systems with the conventional dish (or beaker) setup, but the multiwell plate method allowed for many more repetitions. The proposed system is an alternative for UV-inactivation dose-response assay, especially when screening assays are desired, since it has the advantage of being fast, comprehensive (with a large number of simultaneous replicates) and easily adapted to various applications as UV-LED based photocatalysis experiments, UV effect on biofilm formation and UV-based AOP degradation experiments.
关键词： Water treatment,MS2 coliphage,UV light-emitting diode (UV-LED),E. coli,Multiwell plate
更新于2025-09-23 15:19:57