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Analytical and Monte Carlo comparisons on the optical transport mechanisms of powder phosphors
摘要： In indirect medical imaging systems, the optical transfer properties of powder phosphor materials are affected by the intrinsic mechanisms of light extinction. Light extinction (absorption and scattering) can be described either through theoretical models or with Monte Carlo simulation techniques. The purpose of the present paper is to compare both methodologies and assess the association of their optical parameters by examining either the structural (e.g., particle size) or the optical (e.g., light wavelength) intrinsic properties of the phosphor. Comparisons were carried out for the widely used host Gd2O2S for granular phosphors. The parameters considered in Monte Carlo simulation were: (i) a phosphor layer composed of grains with diameter 4–12 μm, (ii) the light wavelength (420 nm, 545 nm and 610 nm), (iii) the refractive index of the phosphor (real part: 2.3, imaginary part: 10?6 and 10?5), (iv) the packing density 50%. The results were compared with the Swank analytical model, based in Boltzman diffusion equation, by considering three cases for optical coefficients determination with the help of which the Luminescence Efficiency (LE) and the Modulation Transfer Function (MTF) of the phosphor could be predicted. It was found that Swank's model seems more appropriate for estimating the MTF values, presenting a deviation less than 5% in all the frequency range. for: wavelength 420 nm, considering (i) grain size 4 μm and thicknesses above 250 μm, (ii) grain size 12 μm and thicknesses above 300 μm, (b) wavelength 545 nm, grain size 8 μm and thicknesses above 160 μm, and (c) wavelength 610 nm, considering (i) grain size 4 μm and thicknesses above 200 μm, (ii) grain size 8 μm and thicknesses above 120 μm and (iii) grain size 12 μm and thicknesses above 80 μm.
关键词： Optical diffusion,X-ray detectors,Phosphor materials
更新于2025-09-19 17:15:36
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Silica nanoparticles assisted preparation of reddish-yellow emitting Eu2+ activated remote-type CaSrSiO4 phosphor for warm white LED applications
摘要： A reddish-yellow emitting silicate-based remote phosphor has been developed via the wet-solid phase reaction technique. By employing silica nanoparticles (200 nm), Eu2+ doped CaSrSiO4 phosphor was developed and its e?cacy has been examined thoroughly. The developed remote phosphor can get excited over a broad region of the spectrum ranging from ultraviolet to blue (250–500 nm) and as generates a reddish-yellow emission peaked at 580 nm covering a broad range of spectral components (450–800 nm) with a quantum e?ciency of 52%. The thermoluminescence studies of developed remote phosphor exhibit 50% of the stable emission up to 200 °C without any shift in the emission wavelength. The developed remote phosphor was then utilized for the making of a proto-type LED using 450 nm blue-emitting commercial LED. The output emission from the proto-type LED con?rms the production of e?cient warm white light with CCT < 5000 K and CRI > 85.
关键词： Phosphor,LED,Warm white light,Remote phosphor
更新于2025-09-19 17:13:59
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Tunable lanthanide/transition metal ion‐doped novel phosphors for possible application in w‐LEDs: a review
摘要： Lanthanide-based phosphors have been extensively investigated for their possible applications in solid-state lighting technologies especially for white-light-emitting diodes. In this review article emphasis has been laid on discussing the recent developments of phosphors for warm white-light production based on various optical characteristics such as quantum efficiency, thermal stability, short emission decay time, long-term stability, facile synthesis, and low cost of production. We have tried to cover the essential and latest discoveries of the lanthanide/rare earth-doped phosphors after 2010. New generations of narrow-band phosphors have also been included. The optical and material properties of several novel phosphors and their luminescence characteristics have been thoroughly discussed.
关键词： lamp phosphor,w-LED,thermal stability,phosphor
更新于2025-09-19 17:13:59
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Unique Design Strategy for Laser‐Driven Color Converters Enabling Superhigh‐Luminance and High‐Directionality White Light
摘要： Robust ceramic color converters withstanding strong laser irradiations have recently drawn great attention for laser-driven white lighting. However, the local emission within the incident laser spot usually expands to the whole surface area of the ceramics, which definitely makes it hard to achieve white light with high luminance and high directionality. Herein, a new strategy is proposed to solve the problem by elaborately introducing uniform spherical pores (diameter of ≈2 μm) into the phosphor ceramics with controlled contents from 8 to 24.6 vol%. The well-distributed pores, acting as light scattering centers, enable reduction of the luminescent spot size greatly but without any losses in conversion efficiency. By using the high-scattering ceramic color converters with 15% porosity, the light spot diameter is decreased by 46% and the central illuminance is increased by 156%. Moreover, laser-driven white light with an enhanced beam directionality and uniformity is also achieved. A superhigh luminous flux of 7199 lm is realized by using this promising color converter in a rotary mode. The designed high-scattering ceramics with controllable microstructures show great potential for use in extra-high luminance laser-driven lighting and projection.
关键词： light confinement,phosphor ceramics,phosphor wheel,laser-driven lighting,color converters,scattering
更新于2025-09-19 17:13:59
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Mechanistic Insight into Energy Transfer Dynamics and Color Tunability of Na4CaSi3O9:Tb3+, Eu3+ for Warm White LEDs
摘要： We propose a latent energy transfer process in traditional Eu3+, Tb3+-doped phosphors and present a new class of Eu3+, Tb3+-doped Na4CaSi3O9 phosphors, enabled by luminescence decay dynamics that optimize the electron-transfer energy process. Compared with other Eu3+, Tb3+-doped phosphors, the as-synthesized Eu3+, Tb3+-doped Na4CaSi3O9 phosphors show improved large-scale tunable emission color from green to red upon UV excitation, controlled by the Tb3+/Eu3+ doping ratio. Detailed spectroscopic measurements in the VUV-UV-vis region were used to determine the Eu3+-O2- charge transfer energy, 4f-5d transition energies and the energies of 4f excited multiplets of Eu3+ and Tb3+ with different 4fN electronic configurations. The Tb3+→Eu3+ energy transfer pathway in the co-doped sample was systematically investigated, employing luminescence decay dynamics analysis to elucidate the relevant energy transfer mechanism in combination with the appropriate model simulation. To demonstrate their application potential, a prototype white light-emitting diode (WLED) device was successfully fabricated using the yellow luminescence NCSO:0.03Tb3+,0.05Eu3+ phosphor with high thermal stability and a BaMgAl10O17:Eu2+ phosphor in combination with a near-UV chip. These findings open up a new avenue to realize and develop multifunctional high-performance phosphors by manipulating the energy transfer process for practical applications.
关键词： Luminescence,Energy transfer,Phosphor,Luminescence decay dynamics,Rare earth
更新于2025-09-19 17:13:59
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Energy transfer and thermal stability of novel green-emitting Ca3Y(PO4)3:Ce3+, Tb3+ phosphors for white LEDs
摘要： A novel thermally high-stable and high-e?ciency green-emitting Ce3+/Tb3+ co-doped Ca3Y(PO4)3 phosphor has been successfully synthesized via a conventional solid-state reaction. The energy transfer and thermal quenching of Ca3Y(PO4)3:Ce3+, Tb3+ samples were investigated for the ?rst time. The emission spectra of as-prepared samples presented a blue emission band deriving from the 5d-4f transition of Ce3+ and green emission peaks stemmed from 5D4-7FJ (J = 6, 5, 4, 3) of Tb3+ upon 325 nm excitation. By adjusting Tb3+ concentration, the chromaticity coordinates of as-prepared samples could be tuned from (0.165, 0.028) to (0.301, 0.529) because of the energy transfer of Ce3+→Tb3+ ions. It was demonstrated that the energy transfer mechanism from Ce3+ to Tb3+ ions in Ca3Y(PO4)3 host is the electric dipole-dipole interaction by the energy level diagram and the spectral overlap between the emission spectrum of the donor and the excitation spectrum of the acceptor. The energy transfer e?ciency from Ce3+ to Tb3+ ions in Ca3Y(PO4)3 was up to 81%. Beyond that, it a?rmed that the emission intensity at 423 K was about 82% of that measured at room temperature (298 K) according to the temperature-dependent emission spectra. Basing on the above analyses shows that the as-synthesized green-emitting Ce3+/Tb3+ co-doped Ca3Y(PO4)3 phosphors with high energy transfer e?ciency and excellent thermal stability could be used in phosphor-converted white light-emitting-diodes (LEDs).
关键词： Thermal stability,Luminescence,Phosphor,Ca3Y(PO4)3,Energy transfer
更新于2025-09-19 17:13:59
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Preparation of red-emitting BaSiF6:Mn4+ phosphors for three-band white LEDs
摘要： BaSiF6:Mn4t phosphors were synthesized to improve the color purity of phosphor-converted white light-emitting diodes (LEDs). The optimal synthesis conditions for attaining the brightest red emission spectrum from BaSiF6:Mn4t were investigated. The BaSiF6:Mn4t phosphor exhibited a strong absorption band at approximately 465 nm because of the 4A2g → 4T2g transition of Mn4t ions. In addition, the phosphor exhibited three strong emission peaks, at 615, 632, and 650 nm, because of a combination of vibrational shifts and the 2Eg → 4A2g transition in Mn4t is suitable for use as the red-emitting phosphor in three-band white LEDs pumped by a blue LED. The optical properties of BaSiF6:Mn4t were examined under excitation from a commercial blue LED by coating the phosphor onto the blue LED. Similarly, a three-band white LED was also fabricated by coating the red-emitting phosphor BaSiF6:Mn4t and green-emitting phosphor CsPbBr3 onto a commercial blue LED.
关键词： Photoluminescence,Three-band white LED,BaSiF6:Mn4t,phosphor
更新于2025-09-19 17:13:59
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29.4: A laser current control algorithm to avoid color distortion in laser projection displays
摘要： Laser display technology has gradually become an important solution for large screen display. As a mature lighting technology in recent decades, phosphor has been widely used in the field of lighting and display. As a solid-state light source, it has the advantages of low power consumption, environmental protection, rich color and dynamic modulation. The luminescent efficiency of phosphors varies with temperature, which results in the non-linearity of phosphor emission when the light source is dynamically modulated and the color temperature drift of the display image. In this paper, a control model of color temperature of laser TV display changing with laser current and temperature is established. The color temperature of laser TV is corrected by using current compensation control algorithm. The problem of color temperature drift caused by the change of phosphor conversion efficiency with temperature is solved. The color temperature deviation is 1118 K in the brightness range of the light source before compensation. By compensating and controlling the laser current, the ratio of blue light and phosphor is constant when the brightness changes, thus ensuring the color temperature constant when the brightness of the laser light source changes. The color temperature deviation is 50K in the brightness range. By analyzing the different brightness of the display image, the stability of the color temperature is improved.
关键词： laser phosphor,dynamic compensation,color distortion
更新于2025-09-19 17:13:59
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Ca(Mg <sub/>0.8</sub> Al <sub/>0.2</sub> )(Si <sub/>1.8</sub> Al <sub/>0.2</sub> )O <sub/>6</sub> :Ce <sup>3+</sup> ,Tb <sup>3+</sup> Phosphors: Structure Control, Density-Functional Theory Calculation, and Luminescence Property for pc-wLED Application
摘要： A modified structure Ca(Mg0.8Al0.2)(Si1.8Al0.2)O6 (denoted as CMASO) from the evolution of CaMgSi2O6 (denoted as CMSO) codoped with Ce3+ and Tb3+ ions was designed successfully by solid reaction method for application in phosphor-converted white-light-emitting diode (pc-wLED). The Rietveld refinement of these two structures verified the changes derived from the replacement of some of the Mg2+ and Si4+ ions by Al3+ ions. The band gaps were calculated by density-functional theory (DFT) calculation method to verify the change of Al3+ ions replacing further, and the diffuse reflectance spectra (DRS) proved the veracity of the calculation result. The phosphors CMASO:Ce3+ showed blue emission excited by a wider excitation wavelength from 280 nm to 370 nm. The change of structure lead to the absorbable range broaden and the emission peak shifted to longer wavelength, compared with CMSO:Ce3+, although the amount of emitting center was the same. The reason for these phenomena was discussed in detail. The codoped phosphors CMASO:Ce3+,Tb3+ exhibited different emission colors from blue to green as the concentration of Tb3+ ions increased. Combined with commercial red phosphor CaAlSiN3:Eu2+ and ultraviolet LED (UV-LED) chips, the selected appropriate samples achieved white emission. The correlated color temperature (CCT) was 6137 K and the color rendering index (Ra) was 80.5, indicating that they could act as potential phosphors for possible applications in pc-wLED.
关键词： Ce3+,pc-wLED,DFT,luminescence property,Tb3+,Ca(Mg0.8Al0.2)(Si1.8Al0.2)O6,phosphor-converted white-light-emitting diode,density-functional theory
更新于2025-09-19 17:13:59
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Numerical Prediction and Experimental Validation of Multiple Phosphor White LED Spectrum
摘要： White LEDs with single phosphor usually have poor color rendering capability. The emission spectra of the blue LED and the yellow phosphor are narrow as compared with the reference light sources. The red light output is particular low. The color of the objects illuminated by such light source appear not accurate nor natural. Though the luminous efficiency is high, such poor color rendering light sources are not suitable for most general lighting applications. To improve the color rendering properties, multiple phosphors with different emission spectra should be used. For instance, a certain amount of red or orange phosphors may be used to mix with yellow phosphor to broaden the overall spectrum. In this paper, a numerical model is proposed to predict the emission spectra of LEDs with multiple phosphors. The model has considered the excitation and emission spectra of the phosphors, the mixing ratio and re-absorption between the phosphors. To validate the model, white light LEDs with multiple phosphors are fabricated. The spectra are measured and compared with the modeling results. It is found that the proposed model can estimate the emission spectra of LEDs with multiple phosphors with a high degree of accuracy.
关键词： Color Rendering,Spectrum Prediction,Phosphor Characterizations,White Light LED,Multiple Phosphors
更新于2025-09-19 17:13:59