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Synthesis of Silica-Coated Csa??PbBra?? and Csa??Pb(Br0.4I0.6)a?? Quantum Dots With Long Lifetime and Enhancement in Quantum Efficiency for WLEDs Applications: Lightings With High CRI and Displays With Wide Color Gamut
摘要： To focus on developing white light-emitting diodes (WLEDs) for lightings with high color rendering index (CRI), low correlated color temperature (CCT), and the displays with wide color gamut, inorganic perovskite quantum dots (QDs) such as CsPbX3 (X = Cl, Br, I) were the promising candidate owing to the excellent optoelectronic properties such as high quantum efficiency, narrow emission wavelengths, and tunable emission spectrum. Nevertheless, the CsPbBr3QDs in the form of powders or films had a poor air stability and severe decline of quantum efficiency. Therefore, in this article, a new idea was proposed that 0-D green–red perovskite QDs powders such as Cs4PbBr6 and Cs4Pb(Br0.4I0.6)6 with improved quantum efficiency and long lifetime were first developed by silica-coated method and crystal phase transition in low-temperature synthesis. The quantum efficiency in green Cs4PbBr6 powders could be significantly enhanced from 31.41% to 45.87% and red Cs4Pb(Br0.4I0.6)6 powders was 22.79%. Moreover, the as-prepared perovskite QD powders and commercial YAG phosphors combined with blue chips were applied to high-quality WLEDs for lightings and displays. More importantly, the as-fabricated wide Commission Internationale de l’Eclairage (CIE) color gamut WLEDs for displays possessed 115% National Television System Committee (NTSC) coverage rate and luminous efficiency of 51 lm/W under 20-mA driving current. On the other hand, the constructed WLEDs for high-power lightings would generate a warm white light with a luminous efficiency of 38 lm/W, extremely high CRI of 92.8, and low CCT of 3828 K under 350 mA. Hence, the proposed green–red perovskite QD powders had outstanding potential applications in WLEDs.
关键词： white light-emitting diodes (WLEDs),0-D perovskite quantum dots (QDs),backlights of displays,solid-state lightings
更新于2025-09-23 15:21:01
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[IEEE 2018 4th International Conference on Applied and Theoretical Computing and Communication Technology (iCATccT) - Mangalore, India (2018.9.6-2018.9.8)] 2018 4th International Conference on Applied and Theoretical Computing and Communication Technology (iCATccT) - A concept of energy efficient LED lighting using Power-over-Ethernet (PoE) technology
摘要： LED lighting is found universal acceptance for being affordable and energy ef?cient. The next big step for LED lighting is enabling LED ?xtures to work in Internet-of- Things (IoT) infrastructure. Power-over-Ethernet(PoE) standard delivers power and data via a Ethernet cable from a power source such as a hub directly to the network port of a connected powered device, in the case of lighting the powered device can be a LED bulb.In this paper the concept of energy ef?cient LED lighting using PoE technology is discussed in brief.The bene?ts PoE technology provides and challenges that needs to be addressed are highlighted.
关键词： energy,lighting,ef?ciency,light emitting diode,solid state lighting,Power over Ethernet,POE,LED,SSL
更新于2025-09-23 15:21:01
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Dynamic range and resolving power of the Timepix detector to heavy charged particles
摘要： The spectrometric and particle tracking response of the Timepix detector for charged particle detection was examined for energetic (i.e. penetrating) heavy charged particles in a wide range of energies and directions. The aim of this study was to examine the detector’s resolving power including particles approaching the minimum-ionizing regime, in particular energetic protons. The per-pixel energy range, of importance namely for heavy charged particles, was also investigated. This work complements and extends the ongoing task to analyze and describe the response and resolving power of the detector in a wide range of particle types, energy (energy loss) and direction. The methodology of event discrimination in terms of these degrees of freedom was expanded and re?ned. Resolution and event classi?cation were based on analyses of cluster morphology parameters together with spectrometric, tracking and correlated derived quantities such as linear-energy-transfer (LET) and ratio cluster height to cluster path length.
关键词： Particle tracking detectors (Solid-state detectors),dE/dx detectors,Pixelated detectors and associated VLSI electronics,Heavy-ion detectors
更新于2025-09-23 15:21:01
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High Emission Quantum Yield Tb <sup>3+</sup> -Activated Organic-Inorganic Hybrids for UV-Down-Shifting Green Light-Emitting Diodes
摘要： Solid-state light-emitting diodes (LEDs) are driving the lighting industry towards efficient and environmentally friendly lighting and displays. Current challenges encompass efficient and low-cost down-shifting phosphors with tuned emission colors. Green light lies on the low-loss optical transmission window in plastic optical fibers and plays a special role in human and plants circadian rhythm regulation. Moreover, green-emitting phosphors may suppress the ‘green gap’ found in semiconductor-based LEDs. In this work, a UV-photostable Tb(NaI)3(H2O)2, with (1-ethyl-1,4-dihydro-7-methyl-4-oxo-1,8-NaI= nalidixic naftiridine-3-carboxylic acid), was incorporated into tripodal organic-inorganic hybrid materials. The hybrid hosts boost the absolute emission quantum yield from ~0.11 (isolated complex) to ~0.82 (doped hybrid), being the largest value reported for Tb3+-based hybrid phosphors. A green-emitting LED was fabricated by coating a near-UV LED (365 nm) with a Tb3+-activated organic-inorganic hybrid showing pure-green light with Commission International de l’Eclairage color coordinates and an efficacy value of (0.33, 0.59) and 1.3 lm·W?1, respectively.
关键词： near-UV light-emitting diodes,green light-emitting diodes,lanthanides,solid-state lighting,organic-inorganic hybrids
更新于2025-09-23 15:21:01
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Performance of dye-sensitized solar cell (DSSC) using carbon black-TiO2 composite as counter electrode subjected to different annealing temperatures
摘要： Carbon black-TiO2 composite counter electrode was synthesized via solid state method and subsequently annealed at different annealing temperatures (450–550 °C). The composite was investigated as a counter electrode, acting as an alternative to platinum in a dye-sensitized solar cell. The aim is to obtain a higher conversion efficiency of solar energy being converted into electricity. The synthesized sample was structurally characterized by X-ray diffraction and it was found that annealing temperature strongly enhanced the anatase structure of carbon black-TiO2. The surface morphology and grain size were examined by field emission scanning electron microscopy which showed the presence of mesoporous structure; this is very important for high quality dye and electrolyte distribution. Electrochemical studies of carbon black-TiO2 counter electrodes suggest that increasing the annealing temperature may lead to increased charge transfer resistance which could contribute to decreased catalytic activity. The photovoltaic properties of carbon black-TiO2 were observed to be strongly influenced by the annealing temperature; measurements taken at annealing temperature of 525 °C showed the best photovoltaic properties of JSC = 6.10 mA/cm2, VOC = 0.51 V, FF = 0.89 and η = 2.77%.
关键词： Carbon black-TiO2 composite,Solid state method,Counter electrode,Annealing temperature
更新于2025-09-23 15:21:01
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Processing and Study of Optical and Electrical Properties of (Mg, Al) Co-Doped ZnO Thin Films Prepared by RF Magnetron Sputtering for Photovoltaic Application
摘要： In this study, high transparent thin films were prepared by radio frequency (RF) magnetron sputtering from a conventional solid state target based on ZnO:MgO:Al2O3 (10:2 wt %) material. The films were deposited on glass and silicon substrates at the different working pressures of 0.21, 0.61, 0.83 and 1 Pa, 300 °C and 250 W of power. X-ray diffraction patterns (XRD), atomic force microscopy (AFM), UV-vis absorption and Hall effect measurements were used to evaluate the structural, optical, morphological and electrical properties of thin films as a function of the working pressure. The optical properties of the films, such as the refractive index, the extinction coefficient and the band gap energy were systematically studied. The optical band gap of thin films was estimated from the calculated absorption coefficient. That parameter, ranged from 3.921 to 3.655 eV, was hardly influenced by the working pressure. On the other hand, the lowest resistivity of 8.8 × 10?2 ? cm was achieved by the sample deposited at the lowest working pressure of 0.21 Pa. This film exhibited the best optoelectronic properties. All these data revealed that the prepared thin layers would offer a good capability to be used in photovoltaic applications.
关键词： working pressure,Al doped ZnO-MgO powder,RF magnetron sputtering,photovoltaic applications,thin films,solid-state method,optoelectronic properties
更新于2025-09-23 15:21:01
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An all-solid-state lamellar-nanostructured polymer electrolyte in-situ-prepared from smectic liquid crystal for thermally stable dye-sensitized solar cells
摘要： A novel all-solid-state polymer electrolyte based on thiolate/disulfide redox couple was in-situ prepared from a lamellar-assembled liquid crystal precursor for dye-sensitized solar cells (DSSCs). The use of the thiolate/disulfide redox couple allowed the in-situ polymerization, which ensured both preservation of the lamellar nanostructure in electrolyte and sufficient interfacial contact in DSSC. Electrochemical analysis revealed that the lamellar-nanostructured electrolyte possessed charge transport ability and photovoltaic performance quite close to the liquid crystal electrolyte precursor. The resultant all-solid-state DSSCs showed a thermally stable photovoltaic performance with PCE higher than 2% from 35 to 90 °C. The method in using in-situ polymerization of nanostructured liquid crystals to prepare solid-state electrolytes shed a new light for efficient and stable all-solid-state DSSC preparation, especially in large-scale actual application.
关键词： All-solid-state polymer electrolyte,In-situ preparation,Smectic liquid crystal,Dye-sensitized solar cell
更新于2025-09-23 15:21:01
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Morphological, spectroscopic and photocatalytic properties of Eu3+:TiO2 synthesized by solid-state and hydrothermal-assisted sol-gel processes
摘要： Eu3+ doped TiO2 powders were synthesized by solid-state reaction and hydrothermal-assisted sol-gel process. They were characterized by X-ray diffraction, scanning electron microscopy and photoluminescence techniques. Both synthetic procedures yield the pure anatase phase of titania. The excitation and emission spectra and the decay profiles were measured for different thermal treatments of the samples, in order to investigate the effects of the synthesis conditions on the doping mechanism. The photocatalytic activity was investigated by measuring the degradation of methylene blue under UV light irradiation and a correlation between its efficiency and the luminescence performance has been proposed.
关键词： TiO2:Eu,Solid-state,Optical spectroscopy,Anatase,Photocatalysis,Hydrothermal-assisted sol-gel
更新于2025-09-23 15:21:01
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Photoluminescence properties of Ca3B2O6: RE3+ (RE = Dy and Eu) phosphors for ecofrindly solid state lighting
摘要： The phosphors Ca3B2O6:Dy3+ and Ca3B2O6:Eu3+ were prepared by a combustion method. The phosphor was characterized for X- ray diffraction and photoluminescence. The XRD is well matched with the standard JCPDS. Ca3B2O6:Dy3+ phosphor shows two emission bands centered at 481nm and 577nm corresponding to transitions 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2 respectively. Eu3+ doped Ca3B2O6 phosphor gives emission centered at 588nm, 597nm, 614nm and 627 nm having excitation at 396nm. Concentration quenching effect was observed in both the phosphors. Photoluminescence results suggest that phosphor could be used as ecofriendly solid state lighting applications.
关键词： Combustion method,Borate,solid state lighting
更新于2025-09-23 15:21:01
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X-ray scintillator Gd2O2S:Tb3+ materials obtained by a rapid and cost-effective microwave-assisted solid-state synthesis
摘要： In this work, the microwave-assisted solid-state (MASS) synthesis is reported as a rapid, cost-effective and environmental-friendly way to prepare Gd2O2S:Tb3+ X-ray scintillation standards. The preparation procedure employs active charcoal as the microwave susceptor, using a domestic microwave oven without a setup for special gases. The MASS method drastically reduced the synthesis time and energy consumption (up to 97% in nominal power) over previous reports using conventional solid-state methods. A single-step synthesis of 10 min is enough to yield highly crystalline powders starting from Gd2O3 and Tb4O7 precursors and elemental sulfur. In order to obtain 100% pure materials with superior scintillation efficiency, two microwave treatments of 25 min each are required. Due to the reducing CO atmosphere generated in situ by the active charcoal during the microwave synthesis, no Tb4+ impurity was found according to Synchrotron Radiation X-ray Absorption (SR-XAS) experiments. Spectroscopic studies were carried out using SR Vacuum-Ultraviolet (VUV) photoluminescence and SR X-ray Excited Optical Luminescence (XEOL). The material prepared by two-step synthesis exhibited a better scintillation performance owing to higher crystal purity and emission intensity, presenting versatility for technological applications such as X-ray imaging and scintillation bio-probing.
关键词： Synchrotron Radiation,Gd2O2S:Tb3+,Microwave-assisted solid-state synthesis,X-ray scintillation
更新于2025-09-23 15:21:01