Phosphor-converted White LEDs Research Articles

Suppressing the Thermal Quenching Effect via a Cluster Conformer in Copper(I)-Iodide Coordination Polymeric Phosphors for High-Power White LED Lighting.

High-power LED lighting is a crucial challenge due to the notorious thermal quenching (TQ) effect of traditional phosphors at high operating currents, which would result in poor device performance and hamper practical optoelectronic application. Herein, we demonstrate ligand engineering of a cubane- versus staircase-like [Cu4I4] conformer as a node in coordination polymers, which remarkably suppresses the TQ effect of cluster-based photoluminescence. For complex 1 (the formula [Cu4I4(bbimb)2]n) with the cubane-like [Cu4I4] conformer as a node, the metallophilicity interaction enables ultrabright triplet emission with a photoluminescence quantum yield over 82%, and the phonon-assisted detrapping process of excitons effectively suppresses the TQ effect in the wide temperature range. In contrast, the staircase-like [Cu4I4] conformer as a node in complex 2 (the formula [Cu4I4(bbtmb)2]n) exhibits a serious TQ effect over the investigated temperature. Phosphor-converted white LEDs (pc-wLEDs) were fabricated by integrating the cluster-based coordination polymers as a color converter, and their electroluminescence performances were investigated under high bias currents. The prototype pc-wLED device by incorporating the phosphor with the suppressed TQ effect exhibits a continuous rise in brightness under a high bias current of 300 mA. The results demonstrate that ligand engineering of the cluster conformer via suppressing the TQ effect proves efficient in designing an ideal color converter for high-power pc-wLED lighting.

Optimized method of thermoelectric cooler-based thermal management for improving the luminous efficacy of light-emitting diodes

We experimentally performed a method of active cooling for white LED that can reduce the temperature of the LED by using TEC for reducing the temperature of the LED board. The relation of LED board and input power for TEC was investigated to find out the optimized curve of LED board temperature and input power for TEC. Also, the TEC based cooling system was applied for RGBW LEDs. The obtained result is meaningful in LED thermal management, improving the lighting quality and increases the lifespan for both middle and high-power LED types. Full Text: PDF References E.F. Schubert, J.K. Kim, "Solid-State Light Sources Getting Smart", Science, 308, 1274 ¬(2005). CrossRef Q.K. Nguyen, "Emission spectrum modeling of white LEDs light source with using Gaussian function", Photonics Lett. Pol.,15(4), 54 (2023). CrossRef C.C. Sun, S.H. Ma, Q.K. Nguyen, "Advanced LED Solid-State Lighting Optics", Crystals, 10, 758 (2020). CrossRef S.P. Ying, H.K. Fu, W.F. Tang, R.C. Hong, "The Study of Thermal Resistance Deviation of High-Power LEDs", IEEE Trans. Electron Devices, 61, 2843 (2014). CrossRef K. Górecki, P. Ptak, "Compact Modelling of Electrical, Optical and Thermal Properties of Multi-Colour Power LEDs Operating on a Common PCB", Energies, 14, 1286 (2021). CrossRef C.C. Sun, Q.K. Nguyen, T.X. Lee, S.K. Lin, C.S. Wu, T.H. Yang, Y.W.Yu. "Active thermal-fuse for stopping blue light leakage of white light-emitting diodes driven by constant current", Sci. Rep. 12, 12433 (2022). CrossRef Q.K. Nguyen, B. Glorieux, G. Sebe , T.H. Yang, Y.W. Yu , C.C. Sun, "Passive anti-leakage of blue light for phosphor-converted white LEDs with crystal nanocellulose materials", Sci Rep. 13, 13039 (2023). CrossRef N. Bădălan (Drăghici), P. Svasta, C. Marghescu, "A Method for Improving an Active Cooling Solution for LEDs ", IEEE 24th International Symposium for Design and Technology in Electronic Packaging (SIITME), Iași, Romania (2018). CrossRef A. Fan, R. Bonner, S. Sharratt, Y.S. Ju, "An innovative passive cooling method for high performance light-emitting diodes", 28th Annual IEEE Semiconductor Thermal Measurement and Management Symposium (SEMI-THERM), 319-324 (2012). CrossRef D.W. Kim, E. Rahim, A. Bar-Cohen, B. Han, "Direct Submount Cooling of High-Power LEDs", Compon. Packag. Technol., 33, 698 (2010). CrossRef N. Guan, N. Amador-Mendez, A. Kunti, A. Babichev, S. Das, A. Kapoor, N. Gogneau, J. Eymery, F.H. Julien, C. Durand, M. Tchernycheva, "Heat Dissipation in Flexible Nitride Nanowire Light-Emitting Diodes", Nanomater, 10, 2271 (2020). CrossRef S. Li, J.L. Liu, L. Ding, J.X. Liu, J. Xu, Y. Peng, M.X. Chen, "Active Thermal Management of High-Power LED Through Chip on Thermoelectric Cooler", IEEE Trans. Electron Devices, 68, 1753 (2021). CrossRef G.R. Sui, J.J. Chen, H. Ni, Y.Y. Ma, X.M. Gao, N. Wang, "Improvement of LED Performance With an Integrated Thermoelectric Cooling Package", IEEE Access, 8, 116535 (2020). CrossRef

Measurement model of circadian action factor of phosphor-converted white LEDs based on photometric, electrical, and thermal properties

Light stimulus is confirmed to have critical non-visual biological effects on human beings, and thus evaluation of lighting quality should not be limited to traditional visual performance. The circadian action factor (CAF) has been put forward to quantify such non-visual effects of light sources. This paper focuses on studying the photometric, electrical, and thermal properties of widely used phosphor-converted white LEDs (PC-WLEDs), and establishes an indirect measurement model of CAF regarding temperature, current and excitation wavelength. During modeling, the spectral power distribution of PC-WLEDs is described as an extended Gaussian function of the double-color (blue-yellow) spectrum. In verifications, the remarkable consistency is obtained between indirect measurements and direct calculations, while the maximum relative errors do not exceed 2.6% and the mean relative errors do not exceed 0.9%. The proposed measurement model involves a series of optical tests and calibrations, which are simple for LED system designers to comply with. It offers an effective tool to quantify the PC-WLEDs’ non-visual biological effects on human beings, avoiding costly optical instruments and laborious calculations. Furthermore, it provides a potential theoretical foundation for realizing human-centric assessment, regulation and control of artificial lighting.

Passive anti-leakage of blue light for phosphor-converted white LEDs with crystal nanocellulose materials

A phenomenon known as "blue-light leakage" caused by overheating pcW-LEDs has recently been identified, and it poses a risk to users. This study focuses on investigating and optimizing a solution to address this issue. To tackle the problem of overheating and blue light leakage, we explored the application of a specific thermochromic material called crystal nano cellulose (CNC). We introduced CNC inside the epoxy lens of white LEDs. Importantly, under standard conditions, CNC has a negligible impact on the optical properties of the output white light. However, when overheating conditions arise, leading to blue light leakage, the temperature increase triggers a darkening effect in CNC. This thermochromic behavior of CNC allows it to strongly absorb the blue light, resulting in a significant suppression of the output luminous flux. As a result, the lamp dims, which not only prevents the user's eyes from being exposed to harmful bluish light but also serves as an indicator of aging in the pcW-LED. By implementing CNC as a responsive material in the design of white LEDs, this study offers a practical and effective solution to mitigate the negative effects of blue-light leakage caused by overheating. This improvement enhances the safety and comfort of users while also providing an early warning system for the aging of pcW-LEDs.

Recent Advances and Opportunities of Eco-Friendly Ternary Copper Halides: A New Superstar in Optoelectronic Applications.

Recently, the newly-emerging lead-free metal-halide materials with less toxicity and superior optoelectronic properties have received wide attention as the safer and potentially more robust alternatives to lead-based perovskite counterparts. Among them, ternary copper halides (TCHs) have become a vital group due to their unique features, including abundant structural diversity, ease of synthesis, unprecedented optoelectronic properties, high abundance, and low cost. Although the recent efforts in this field have made certain progresses, some scientific and technological issues still remain unresolved. Herein, a comprehensive and up-to-date overview of recent progress on the fundamental characteristics of TCH materials and their versatile applications is presented, which contains topics such as: i) crystal and electronic structure features and synthesis strategies; ii) mechanisms of self-trapped excitons, luminescence regulation, and environmental stability; and iii) their burgeoning optoelectronic devices of phosphor-converted white light-emitting diodes (WLEDs), electroluminescent LEDs, anti-counterfeiting, X-ray scintillators, photodetectors, sensors, and memristors. Finally, the current challenges together with future perspectives on the development of TCH materials and applications are also critically described, which is considered to be critical for accelerating the commercialization of these rapidly evolving technologies.

Structural, optical, elemental and photometric properties of Sm3+ activated Ca3Ga4O9 oxide phosphors for WLEDs

Solid-state lighting systems rely on the exceptional characteristics of phosphor-converted LEDs, including long lifetime, low energy consumption, and high brightness. This study focuses on the synthesis of Sm3+ activated Ca3Ga4O9 (CGO: Sm3+) orange-red emitting oxide phosphors using the solid-state reaction method. X-ray photoelectron spectroscopy was used to analyze the nature of bonding with the dopant ion and oxidative states of the elements in the structure. Scanning electron microscopy and energy dispersive spectroscopy revealed agglomerated particles with a flake-like structure in the Sm3+ doped sample. The optical properties of the samples were investigated using UV-Visible diffuse reflectance and photoluminescence excitation and emission analyses. The Sm3+ doped samples showed maximum excitation at 404 nm and 479 nm, with corresponding energy level transitions of 6H5/2 - 6P3/2 and 6H5/2 - 4I11/2, respectively. Emission spectra exhibited four emission maxima at 564, 601, 645, and 708 nm, representing the 4G5/2 - 6H5/2, 4G5/2-6H7/2, 4G5/2-6H9/2, and 4G5/2-6H11/2 transitions of Sm3+ ions. The Kubelka-Munk function was used to calculate the optical energy gap values. Photometric parameters, including color coordinates, correlated color temperature, and color purity, were determined. The CIE chromaticity coordinates of CGO: Sm3+ were found in the orange-red region, indicating its potential as a promising candidate for use in phosphor-converted white LEDs applications. The study concludes that Sm3+ activated CGO phosphors have great potential for use in solid-state lighting systems.

Specifying Non-White Light Sources in Outdoor Applications to Reduce Light Pollution

ABSTRACT Anthropogenic (“human-generated”) light at night (ALAN) from outdoor lighting produces light pollution and as a result causes a range of deleterious responses in humans, plants, and animals. An emerging strategy to combat light pollution, especially sky glow, is to use “amber” LEDs in lieu of phosphor-converted white LEDs with high correlated color temperatures. Importantly, however, there is no standardized terminology or chromaticity designation that is applicable to “amber” LED lighting products for outdoor illumination. In this work, we propose a specification structure for light sources with nonstandard chromaticities to increase the precision of language used in the architectural lighting industry and demonstrate that light sources with well-defined chromaticity ranges outside of the ANSI C78.377–2017 quadrangles may be useful for reducing the portion of relative sky glow related to light source spectral power distribution. We encourage lighting standards development organizations to consider standardizing such a system.

One-Pot Synthesis of Dual Color-Emitting CDs: Numerical and Experimental Optimization towards White LEDs.

Carbon Dots (CDs) are fluorescent carbon-based nanoparticles that have attracted increasing attention in recent years as environment-friendly and cost-effective fluorophores. An application that can benefit from CDs in a relatively short-term perspective is the fabrication of color-converting materials in phosphor-converted white LEDs (WLEDs). In this work we present a one-pot solvothermal synthesis of polymer-passivated CDs that show a dual emission band (in the green and in the red regions) upon blue light excitation. A purposely designed numerical approach enables evaluating how the spectroscopic properties of such CDs can be profitable for application in WLEDs emulating daylight characteristics. Subsequently, we fabricate nanocomposite coatings based on the dual color-emitting CDs via solution-based strategies, and we compare their color-converting properties with those of the simulated ones to finally accomplish white light emission. The combined numerical and experimental approach can find a general use to reduce the number of experimental trial-and-error steps required for optimization of CD optical properties for lighting application.

Structure and Luminescence Studies of a Ce3+-Activated Ba5La3MgAl3O15 Green-Emitting Phosphor

Novel green-emitting Ba5La3MgAl3O15:Ce3+ (BLMAO:Ce3+) is successfully obtained by a solid-state reaction. In this study, BLMAO, which is inspired from the Ba6La2A1.5Fe2.5O15 crystal structure, shows a green emission approximately peaked around 500 nm under near-ultraviolet light excitation at 412 nm by Ce3+ doping. Moreover, internal and external quantum efficiencies of BLMAO:0.02Ce3+ are found to be 27 and 22%, respectively. The emission peak deconvolution and Dorenbos model calculation reveal that the Ce3+ ion occupies on two different crystallographic sites. The potential of BLMAO:Ce3+ for phosphor-converted white LEDs (pc-wLEDs) is systematically evaluated from the results of Rietveld refinement and luminescence measurement.

Near ultraviolet excitable cyan-green phosphors of Ba6La2Al3ScO15:Ce3+ and Ba6La2Al3ScO15:Ce3+,Tb3+: investigations on the crystal structure, site assignment of Ce3+ and Tb3+ ions, and an energy transfer process from Ce3+ to Tb3.

An energy transfer from Ce3+ to Tb3+ is feasible in energy transition processes for the development of optical devices, especially phosphor-converted white LEDs (pc-wLEDs). Most of the energy transfer phosphors co-doped with Ce3+ and Tb3+, unfortunately, have weak absorption under a near-ultraviolet light of around 405 nm and blue light excitation, making them incapable for use as near ultraviolet or blue LEDs. In this study, novel energy transfer luminescent materials, Ba6La2Al3ScO15:Ce3+,Tb3+, isostructural with existing Ba6La2(Al,Fe)4O15, were successfully synthesized through a conventional solid-state reaction as a single phase. The phosphors showed a broad cyan emission of Ce3+ and narrow green emissions of Tb3+ under a near-ultraviolet light of 405 nm, which was nearly located at an emission wavelength of near-ultraviolet LEDs. The occurrence of energy transfer from Ce3+ to Tb3+ was evidenced by emission lifetime measurements. The lifetime analysis based on formulated energy transfer models, such as Inokuti-Hirayama, Yokota-Tanimota and Martin models, revealed that an energy transfer process from Ce3+ to Tb3+ took place dominantly by a dipole-dipole interaction with low migration among the donors of Ce3+.

Temperature-Dependent Electroluminescence of Phosphor-Converted White LEDs With K₂SiF₆:Mn⁴⁺ Below Room Temperature

High-efficiency Mn <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4+</sup> -activated red phosphor of K <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> SiF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> :Mn <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4+</sup> synthesized at low temperature was utilized to fabricate phosphor-converted white light-emitting diodes (pc-WLEDs). Temperature-dependent electroluminescence (EL) measurements were undertaken at a constant forward voltage mode. A large negative-thermal-quenching (NTQ) effect is demonstrated for the luminescence intensity of this kind of red phosphor in the temperature range of 100–300 K. It is found that its enhancement rate is several times higher than those of the blue chip and the green component, such that the overall color of the pc-WLED shows a wide color gamut in the studied temperature range. By utilizing this outstanding NTQ property of the red phosphor, a color rendering index up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{R}_{\mathrm {a}}=93$ </tex-math></inline-formula> is obtained for the high-brightness pc-WLED with relatively low blue light from the LED chip.

Efficient and tunable Mn2+ sensitized luminescence via energy transfer of a novel red phosphor Ca19Mn2(PO4)14: Eu2+ for white LED

The exploration of efficient and high-purity red phosphors is an urgent need in LED development. Due to the compact and compositional-tunable structure of whitlockite compound, manganese-based Ca19Mn2(PO4)14 is chosen as phosphor host for Eu2+ sensitization. Rietveld refinement, steady-state spectra, decay lifetime analysis and temperature-dependent emission spectra were investigated and clearly discussed. Under 360 nm excitation, Ca19Mn2(PO4)14: Eu2+ shows a strong Mn2+ sensitized emission at 655 nm with FWHM of 82 nm, benefiting from the short-distance-induced high-efficient Eu2 -Mn2+ energy transfer. Emission engineering of Ca19Mn2(PO4)14: Eu2+ is achieved by Sr2+ co-doping, leading to both tunable peak wavelength (ranging from 650 to 610 nm) and improved intensity (130% of original value). Moreover, Ca19Mn2(PO4)14: Eu2+ exhibits a promising thermal stability where only 40% of emission intensity is lost at 200 °C. Finally, we explored the working performance of the fabricated RGB phosphor-converted white LED. The present work indicates that Ca19Mn2(PO4)14: Eu2+ phosphor is of great potential as a promising and efficient red phosphor in phosphor-converted white LED.

Insights into structural and spectroscopic characterization of Sm3+ doped orange rich red emitting CsMgPO4 phosphors

In the present study, Sm3+ activated inorganic orthophosphate CsMgPO4 (CSMP) phosphors were prepared by adopting a solid-state reaction method. The structural phase purity and morphological features were studied by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM), respectively. The molecular structure and vibrational modes were substantiated with the Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy characterization. The optical bandgap of the host and Sm3+ doped phosphors was deduced from the diffused reflectance (DR) spectra with a typical value of 5.72 eV and a small variation is observed with increasing concentrations. A systematic study of photoluminescence (PL) properties of Sm3+ doped CSMP phosphors was carried out. From the room temperature excitation and emission spectra, it is found that the phosphor emits in the orange rich red light under the suitable excitation of 402 nm in the UV region and concentration quenching occurs at x = 0.02 doping level. The emission peaks observed at around 562, 598 and 644 nm confirm the characteristic Sm3+ 4f-4f transitions. The temperature-dependent photoluminescence (TD-PL) of the x = 0.02 (optimum doping) is recorded from 30 to 210 °C, showing good thermal stability even at 150 °C. The thermal quenching mechanisms are discussed based on the configuration coordinate model of excitation and emission. The prepared phosphors are found to exhibit near thermal stability compared to the commercially available red phosphors. PL decay time and quantum efficiency were measured. The colour coordinates are found to lie in the orangish-red region of the colour space. Thus the prepared phosphors CSMP:x Sm3+ can be useful as a red component in designing UV excitable chip-based phosphor-converted white LED applications.

Simulation of optical behavior of YAG:Ce3+@SiO2 phosphor used for chip scale packages WLED

YAG:Ce3+ yellow phosphor are particularly used luminescent materials to produce white light in phosphor-converted white LED (pc-WLED). Surface coating of YAG phosphor is the main concern for desired optical performance of the phosphors. Many scholars conducted various experimental analysis on the surface coating of phosphors to improve yellow emission, but the theoretical explanation by which phosphor coating could help improving light efficiency has not yet been studied. In this paper, based on Mie theory, the optical constants such as scattering coefficient, absorption coefficient and asymmetry parameter of YAG:Ce3+ phosphor and YAG@SiO2 (YAG:Ce3+ phosphor surface coated with nano-SiO2 layer) were calculated. An optical configuration of chip scale packages (CSP) WLED was constructed by coupling YAG:Ce3+ or YAG@SiO2 phosphors with a LED laser. Based on the optical parameters calculated by Mie theory, the luminescent properties of YAG:Ce3+ and YAG@SiO2 WLED were simulated by Monte Carlo method. The results showed that a thin SiO2 coating layer on YAG phosphor result in an overall increase in luminous performances compared with original YAG WLED. The absorption coefficient of phosphor is the main concern affecting the light emission in WLED. Due to the fact that YAG@SiO2 possess higher 460 nm absorption coefficient (460μabs), it could absorb more blue light than YAG, thereby it has a 1.2% higher conversion efficiency than YAG, finally the enhanced luminous efficiency of YAG@SiO2 WLED is obtained. The results obtained in this work provides a potential method in future WLED packaging designing.

Efficient Broadband Yellow-Green Emission of Vacancy Halide Double Perovskites Through the Ion-Exchanged Strategy.

Broadband high-efficiency luminescent materials have become a hot spot in lead-free perovskite research. There are relatively few broadband yellow-green phosphors with both ultraviolet and blue excitation ranges, which make them more suitable for phosphor-converted white LEDs. Through the ion-exchanged strategy, Cs2Hf1-xTexCl6 (CH1-xTxC) vacancy halide double perovskites were successfully prepared at room temperature. Using different excitation ranges of CH1-xTxC, two types of high-quality white LEDs are obtained. By combining density functional theory calculations and experiments, it is proved that this bright broadband yellow-green emission (photoluminescence quantum yield of 83.46%) is not only derived from the ion transitions of Te4+ but also exhibits the inherent characteristics of self-trapped exciton emission. Our results not only broaden the application fields of lead-free halide perovskites but also provide further insights into the luminescence mechanism.

A NOVEL SOLAR SIMULATOR BASED ON COMBINED NATURAL-WHITE AND INFRARED LIGHT EMITTING DIODES

Despite the continuous trend of an LED solar simulator development, there was little to be found in the application of a phosphor-converted natural white LED (pc-nWLED) for construction. This article reported the design and construction of an LED solar simulator which combined a pc-nWLED with infrared LEDs. The objectives of this study are to determine the performance of a novel solar simulator including non-uniformity (SNE), temporal stability (TIE), and spectrum mismatch (SM). This is followed by an experimental study of the correlation between the LED’s temperature and SNE. A spectroradiometer, pyranometer, and a custom-made non-uniformity measurement system were applied to test the performance characteristics of this solar simulator. The results indicated that the proposed solar simulator could achieve the AAA class. The results showed 0.90-1.08 of SM, 0.83% TIE, and 1.34% of SNE. The SNE indicated the positive significant correlation with the LED’s temperature, with an approximate of +0.043% per °C. A good cooling system for the LED module was necessary to maintain constant light uniformity. The blue-chip phosphor converted white LED combination with color mixed of 730 nm, 850 nm, and 940 nm could emit a light spectrum that was very close to the reference spectrum of about 99.6%.

Review of optical design for vehicle forward lighting based on white LEDs

We introduce a current development in optical design for vehicle forward lighting based on solid-state lighting, in particular, phosphor-converted white LEDs. The vehicles include bicycles, bikes, and automobiles. Although the requirements regulating different vehicles are different, the low beam always requires a high-contrast cutoff line. Three optical design approaches are discussed; these include a projection lens incorporated with a baffle or beam shaper, multisegment reflectors, and complex lenses. A new design approach called light field management technology for the multisegment reflector is introduced. In addition, the possible related manufacturing errors and the robustness of different optical approaches are analyzed. Finally, we introduce three approaches to adaptive forward lighting that provide a driver with brighter and clearer vision without inducing glare to people on the roadway. The application of video projection technology to roadway illumination could be a trend of vehicle forward lighting based on solid-state lighting.

A near UV-excited abnormal broad yellow emission phosphor Ba2CaB2Si4O14:Eu2+ for white-light LEDs

Phosphor-converted white LEDs are realized by combining blue InGaN chips with yellow and red emitting materials. Due to the lack of efficient red phosphor materials, we can design a broadband yellow phosphor material containing as many red components as possible. We found an abnormal broadband yellow-emitting Ba2CaB2Si4O14:Eu2+ borosilicate phosphor inspired by natural minerals, which has been synthesized by traditional high temperature solid-state method. The structural information and photoluminescence characteristics of Ba2CaB2Si4O14:Eu2+ were characterized in detail, and applied to the fabrication of white LED devices. Excited by near ultraviolet light at 365 nm, it displays a wide emission band from 400 to 800 nm centered on the 595 nm peak. White LED devices were fabricated by physically mixing the yellow phosphor Ba2CaB2Si4O14:Eu2+ and synthesized blue phosphor BaMgAl10O17:Eu2+ with 365 nm UV chip as excitation. The correlation color temperature (CCT) value and the chromaticity coordinates of the fabricated WLED devices were found to be 5522 K and (0.3293, 0.3036) respectively. In conclusion, Ba2CaB2Si4O14:Eu2+ has great potential in the preparation of near UV excited white LEDs.

A potential high color purity and thermally stable red-emitting phosphor based on Tb3+ and Eu3+ co-doped sodium yttrium borate: Synthesis and luminescence spectroscopic characterization

A series of Tb3+ and Eu3+ single- and co-doped Na3Y(BO3)2 (NYB) was prepared by the solid-state reaction method and characterized their structural, thermal and photoluminescence properties while focusing on the development of efficient narrow-band red-emitting phosphors for near-UV chip-based phosphor-converted white LED (pc-WLED). Luminescence spectroscopic and decay kinetics studies of NYB:Tb3+, Eu3+ sample series demonstrated an occurrence of energy transfer from Tb3+ to Eu3+ with its efficiency dependent on Eu3+ concentration and temperature. The highest quantum yield of 83.5% was observed for NYB:5.0%Tb3+, 40%Eu3+ composition with excellent thermal stability. The phosphor was finally tested for the use as a red phosphor component in pc-WLED, which demonstrated a high color rendering index of 84.7. The phosphor is a good modelling composition for the development of wider family of narrow-band red-emitting phosphors based on Tb3+/Eu3+ co-doped inorganic oxides for application in pc-WLED.

A single host phosphor Ca3(SiO3)3:Eu2+, Mn2+ with good monodispersity for phosphor-converted white LEDs

Abstract A single host phosphor Ca3(SiO3)3:Eu2+, Mn2+ (CSO: Eu2+, Mn2+) with good monodispersity has been synthesized by high temperature solid state reaction combined with precursor, using porous silica as template and raw material. The phase, size and surface morphology of the phosphor were measured by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Luminescence properties were characterized by photoluminescence excitation (PLE) and emission spectra from room temperature to 480 K. CSO: Eu2+ has strong excitation band in UV region and emits blue light. To compensate for the lack of orange-red emission region and avoid using multiple phosphors, Mn2+ ions are introduced into the Ca2+ sites. The remarkable enhancements of the orange band attributed to an efficient nonradioactive energy transfer from Eu2+ to Mn2+, which has been testified by the photoluminescence spectra and fluorescence decay dynamics. The emitting light of Eu2+, Mn2+ co-doped CSO could be modulated from cool white to warm white by changing the molar ratio of Eu2+ and Mn2+.