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Polyol derived Bi3+ and Er3+ co-doped lanthanum oxide nanophosphors for display & LED applications
摘要： Color tunable luminescence was observed from Bi3+ and Er3+ co-doped La2O3 nanophosphor. The nanophosphors were prepared using cost effective and low temperature polyol route. The crystal structure, morphology, photoluminescence (PL) and were investigated in detail. Hue of Color changed which is observed by PL emissions on heating, La2O3:Bi3+, Er3+ phosphor powders from 700 to 900 (cid:1)C. The observed emission peaks in PL from phosphor powder materials were assigned to either the broad emission originating from the transition in Bi3+ or the visible emission peaks originating transition from the Er3+ ions. All emission peaks of PL are plotted using CIE coordinates.
关键词： Luminescence,Phosphor,CIE,Bismuth co-doped,Binary oxide,Tunable
更新于2025-09-12 10:27:22
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Efficiency in Street Lighting Projects by Employing LED Luminaires and Mesopic Photometry
摘要： This paper discusses the importance of adapting conventional photometric quantities when lighting systems with low luminance levels are under analysis, as public lighting or external lighting in general. In this sense, it is presented an alternative methodology for lighting projects in street lighting, considering the mesopic photometry. The CIE recommendation 191:2010 proposes correction factors that convert conventional photometric quantities (photopic) into quantities adapted to the corresponding mesopic level. However, a necessary parameter to obtain these correction factors is the relationship between the scotopic and photopic light fluxes of a light source (S/P ratio), which requires special equipment that it is not easily available to engineers, technicians and lighting designers. Thus, this paper proposes a general equation that provides the S/P ratio as a function of the correlative color temperature and the color rendering index of the light source, which are information provided in the manufacturers’ catalogs or electric lamp packages. To illustrate the application of the experimentally derived relationship, a typical street lighting project is considered, specifically a retrofit from HPS lamps to modern LED luminaires. In this case, the conventional routine must be changed, allowing the adaptation of conventional quantities to mesopic quantities without need for specialized equipment. The case study evidences that the use of mesopic photometry in conjunction with more appropriate technologies, such as LED luminaires, lead to a higher energy efficiency of the system.
关键词： Scotopic/photopic ratio,Human visual system,Mesopic vision,CIE 191:2010 report,Street lighting,Photometry,outdoor lighting,energy efficiency
更新于2025-09-12 10:27:22
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Structural and luminescence properties of Dy3+-doped alkali fluoroborophosphate glasses for white LEDs applications
摘要： A new series of Dy3+-doped alkali fluoroborophosphate glasses were prepared by conventional melt quenching technique, and their structural and optical properties were investigated through XRD, FTIR, optical absorption, luminescence and decay measurements. The X-ray diffraction pattern reveals the amorphous nature of the prepared glasses. The fundamental stretching vibrations of various borate (BO3 and BO4) and phosphate (PO4) networks were identified through the FTIR analysis. The nature of the metal–ligand bonding and the electronic band structure has been investigated using the absorption spectra. The Judd–Ofelt (JO) intensity parameters (X2, X4 and X6) were evaluated, and the experimental oscillator strength values were also calculated. Using the JO intensity parameters, radiative properties like radiative transition probability (A), stimulated emission cross section (rE) and branching ratios (bR) for the emission transitions of the Dy3+ ions have been calculated. The luminescence spectra exhibit two visible bands of 4F9/2 → 6H15/2 (Blue) and 4F9/2 → 6H13/2 (Yellow). The decay time of the 4F9/2 level has been measured from the decay profiles and compared with the calculated lifetimes. The yellow-to-blue (Y/B) ratios and color coordinates have been calculated from the luminescence spectra and can be considered for white light emitting diodes applications.
关键词： Absorption,CIE diagram,Melt quenching technique,Rare-earth,Photoluminescence
更新于2025-09-11 14:15:04
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Eu3+-doped fluoro-telluroborate glasses as red-emitting components for W-LEDs application
摘要： From 0.1 up to 2.5 mol% Eu3t-doped fluro-telluroborate glasses as red light-emitting components for white-light-emitting diodes (WLEDs) were investigated. Non-periodicity in the atomic arrangements was studied through the XRD pattern. The photoluminescence (PL) spectra were recorded under blue light (464 nm) excitation and analyzed. All the PL spectra exhibit an intense peak at 612 nm for 5D0 → 7F2 transition, revealing their red photoemission. Optimal PL emissions were achieved for 1.0 mol% Eu3t-doped sample. The CIE chromaticity coordinates for all the glasses (x ? ~0.69, y ? ~0.30) fall within the red color region. The J?O parameters (Ω2, Ω4) were calculated following the emission spectra of Eu3t-doped samples and the intensity parameters (Ω2>Ω4), as well as the high asymmetry ratio (R/O), indicate the low ionicity in all the studied glasses. Using the J-O parameters, several radiative features like total emission transition probability (AT), branching ratios (radiative (βR) & experimental (βexp)), stimulated emission cross-section (σEP), gain bandwidth (σEP × λeff), and optical gain (σEP × τrad) were evaluated. All the luminescence decay curves fit well to non-exponential function and decay times were decreased at Eu3t concentration >0.5 mol%. The evaluated σEP = 19.684 × 10?21 cm2, βexp = 0.759, τexp = 1.325 ms, minimum non-radiative relaxation, WNR = 296/s, and 60.78% of quantum efficiency (η) for 1.0 mol% Eu3t-doped glass for 5D0 → 7F2 transition indicates its promising features for red light-emitting optical devices and also as a red component in WLEDs.
关键词： Luminescence features,Decay lifetimes,Eu3t,White LEDs,Radiative properties,CIE chromaticity coordinates
更新于2025-09-11 14:15:04
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Physical, structural, thermal and spectroscopic investigation of Sm2O3 doped LAB glasses for orange LED
摘要： In this article, Sm2O3 doped Lithium Alumino-borate (LABS) glasses were prepared by melt-quench technique. Physical, structural, thermal and spectroscopic properties are investigated by various techniques. The emission spectra consist of three sharp peaks at 562.5, 599, 645.5 nm within the 4f electronic configuration of Sm3+ ions and two feeble emission peaks at 691, 711 nm of Sm2+ ion at 402 nm excitation. Among all prepared glass samples, glass doped with 0.5 mol % Sm2O3 (LABS-4) shows highest emission intensity with CIE chromaticity coordinates x = 0.55 and y = 0.44 in the orange zone of the chromaticity diagram. The CIE plot and the images of glass samples show; the glass doped with 0.5 mol % Sm2O3 emit intense orange light at 402 nm excitation and can be useful for intense orange LED application.
关键词： CIE Chromaticity,Orange emission,LABS glasses,Sm2O3,Photoluminescence
更新于2025-09-11 14:15:04
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Photoluminescence characteristics of Pr3+ doped PbGdB7O13 as a new red emitting phosphor
摘要： A red phosphor Pr3+ doped PbGdB7O13 was synthesized by high temperature solid state reaction. The effect of Pr3+ doped concentration on the luminescent properties of the phosphor was investigated. The emission spectrum includes an apex at about 607 nm, corresponding to the 3P0→3H6 transition of the Pr3+ ion activator. For PbGd1-xB7O13:xPr3+, the emission peak intensity first increases with the increase of Pr3+ concentration, and reaches the maximum when the Pr3+ concentration is 0.02, and then decreases with the increase of Pr3+ concentration. The CIE coordinates of the PbGdB7O13:0.02Pr3+ phosphor was calculated to be (0.6332, 0.3651), falling into the red color. Therefore, there is a potential application on display, indication or illumination.
关键词： Photoluminescence,High temperature solid state reaction,CIE,Borate
更新于2025-09-10 09:29:36