Phosphor For White Light-emitting Diodes Research Articles

Investigation of structural, optical, dielectric, and electrical properties of NaMn4(PO4)3 (NMP) with fillowite-type structure

We synthesized sodium tetra manganese phosphate, NaMn4(PO4)3, by a solid-state method at a temperature of 900 °C for a duration of 10 h. The application of Rietveld analysis to the PXRD patterns revealed that the sample synthesized show the small amount of the secondary phase (Mn2P2O7). The NaMn4(PO4)3 compound belongs to the trigonal system, namely the R-3 space group. The powder's morphology was examined using scanning electron microscopy (SEM), which revealed an average grain size of approximately 7 μm. The powder underwent elemental analysis using energy dispersive X-ray spectroscopy (EDS), which confirmed the uniformity of the sample. Raman and Fourier transform infrared (FTIR) spectroscopies reveal the distinctive spectral peaks associated with P-O bonds in the (PO4)3- functional group. The optical bandgap energy of 1.57 eV was calculated using the diffuse reflectance technique with the Kubelka-Munk function and Tauc's relation. The chromatic coordinates of NaMn₄(PO₄)₃ suggest that the sample can generate blue-purple light, rendering it appropriate as a red phosphor in white light-emitting diodes (LEDs). Integrating this red emission with blue and green light from additional LED components might enhance the overall color quality and efficiency of white light generation. The dielectric properties of NMP exhibited characteristics that were consistent with ionic conductivity. The Nyquist plot displayed a conspicuous semicircle, indicating the presence of a dominant singular process, most probably linked to the bulk grain. The material demonstrates a significant degree of conductivity, with a measured value of around 3.72 × 10–4 S·cm-1 at a temperature of 300 °C.

Photoluminescence investigations on Sm3+/Eu3+ co-doped Sr3NaSbO6 nanorod-shaped red phosphor for W-LEDs and indoor plant growth LEDs

Red phosphors have garnered an important role in white light-emitting diodes (W-LEDs). Herein we report the structural and luminescent properties of red-emitting Sr(3-x-y)NaSbO6: xSm3+/yEu3+ (SNSO: xSm; yEu) phosphors. Under 350 nm excitation, phosphors emit intense red emission peaking around 689 nm owing to the SNSO host emission. Optimized singly doped SNSO: 0.1Sm and SNSO: 0.2Eu phosphors have intense orange-red and red emissions under 405 and 305 nm excitations respectively. For the codoped SNSO: 0.1Sm; yEu phosphors (y = 0.1, 0.15, 0.2, 0.25, and 0.3 mol), the emission peaks of the host, Sm3+, and Eu3+ ions were present. The energy transfer from the host to Sm3+/ Eu3+ ions and from Sm3+ to Eu3+ ions was identified to be via dipole-quadrupole and quadrupole–quadrupole interactions respectively. Effective red tuning along with high color purity and warm CCT values suggest the suitability of prepared nanorod phosphors for W-LEDs and indoor plant growth LEDs.

Tunable luminescence in SrLaGaO4:Bi3+/Eu3+ phosphors via Bi3+ → Eu3+ energy transfer

Exploring oxide-based dual-emission phosphors containing blue-cyan and red emission is essential to improve luminescence performance of white light emitting diodes (WLEDs). Bi3+ ion is one of widely used luminescence centers that can emit light from ultraviolet to red region according to matrix material, and Eu3+ is one of characteristic red-emitting centers. In the current studies, we fabricated Bi3+/Eu3+ single doped and codoped SrLaGaO4 phosphors and investigated their phase and luminescence performance. Exciting at 320 nm, the Bi3+/Eu3+ single doped SrLaGaO4 showed blue and red emission, respectively. And Bi3+ → Eu3+ energy transfer occurred via the electric dipole-dipole interaction in SrLaGaO4:Bi3+/Eu3+ phosphors, which brings about tunable luminescence of them. White light was generated by the SrLaGaO4:Bi3+/Eu3+ phosphors. The potential applications of the SrLaGaO4:Bi3+/Eu3+ phosphors in WLEDs were surveyed.

Application of KBaYSi2O7:Bi3+,Eu3+ Phosphor for White Light-Emitting Diodes with Excellent Color Quality

This paper examines the properties of two phosphor materials synthesized via utilizing the sol gel method: KBaYSi2O7:Bi3+ (KBYS:Bi) phosphor providing cyan/deep-blue emission and KBaYSi2O7:Bi3+,Eu3+ (KBYS:Bi,Eu) phosphor exhibiting tunable emission from near-UV to red. The optimal doping concentrations for Bi3+ and Eu3+ are 0.2% and 3.5%, respectively. It is found that the ability to give discrepant emission peaks under different excitation sources of the KBYS:Bi phosphor is attributed to the occupancy of Bi3+ in different cation hosts. Meanwhile, co doping the Eu3+ and Bi3+ into the KBYS host leads to red and cyan emission regions, enabling the emission tunability of the KBYS:Bi,Eu phosphor. KBYS:Bi,Eu phosphor was then used in combination with YAG:Ce3+ and blue chips to fabricate a white light emitting diode (LED) model. The particle sizes of KBYS:Bi,Eu phosphor are adjusted to examine its influences on the LED properties. With increasing particle sizes (≥12 µm), the KBYS:Bi,Eu phosphor can improve the scatter efficacy, transmission power, lumen output, and color performance (rendition and uniformity). Both KBYS:Bi and KBYS:Bi,Eu phosphors are promising luminescent phosphors that can be combined with other phosphor with different emission colors to obtain the full-spectrum or tunable white light for LEDs.

Eu3+ doped Ca3LiSbO6 and Eu3+, Li+ co-doped Ca3LiSbO6 phosphors for white light-emitting diodes

Novel antimonate Ca3LiSbO6: xEu3+ red phosphor was synthesised using a high-temperature solid-phase reaction. The effect of Eu3+ doping concentration on its crystal structure and luminescence performance was investigated. It was found that Eu3+ was at the inversion symmetry site in the lattice of Ca3LiSbO6. To improve the luminescence performance of Ca3LiSbO6: 0.05Eu3+ red phosphor, Ca3LiSbO6: 0.05Eu3+, xLi + red phosphor was synthesised. The doping of Li + can correct the charge difference generated by the substitution of Ca2+ by Eu3+, reduce the generation of defects, enhance the local symmetry of the luminescence centre of Eu3+, improve the structural rigidity, and thus enhance the luminous intensity of the phosphor. At 423 K, the luminous intensity of this phosphor was 68 % of the initial temperature, which was higher than that of the phosphor without the charge compensator Li+ (60 %), indicating that Li+ improved the thermal stability of the phosphor.

Comprehensive investigation of Y2Si2O7:Eu3+ nanophosphors for w-LEDs: Structural, Judd-Ofelt calculation and photoluminescent characteristic with high color purity and thermal stability

In recent decades, numerous red phosphors have been designed and developed. Nevertheless, many of them are unsatisfactory due to their low brightness and poor thermal stability. Look at these shortcomings; present study reports on Eu3+ doped Y2Si2O7 (YPS) phosphors, synthesized through low temperature based urea assisted gel-combustion method. Comprehensive investigations were conducted on phase purity, luminous characteristics, energy transfer mechanism, quantum efficacy, morphology, elemental makeup, band gap and thermal stability. XRD analysis was employed to verify the preparation of Y2Si2O7 matrix with triclinic structure (P-1 space group). Morphology and elemental investigations of the fabricated materials was evaluated via TEM and EDX techniques respectively. Under the illumination at 393 nm, the most strong emission band is shown in PL spectra at 613 nm (electric dipole 5D0→7F2 transition). Additionally, the dipole-quadrupole (d-q) interaction was found to be the predominant route of energy transfer among nearby Eu3+ ions and it was concluded that 3 mol % was the optimal doping concentration of Eu3+ ions. The Judd-Ofelt (J-O) theory was used for current phosphors in order to establish their Ω2 and Ω4 with other radiative parameters. The assessment of thermal stability yielded highly promising results with activation energy of 0.241 eV. Present research indicates that Y2Si2O7:Eu3+ is a promising candidate of red emitting phosphor for white light-emitting diodes.

Antimony doping towards fast digital encryption and decryption and high-efficiency WLED in zero-dimensional hybrid indium chlorides

Lead-free metal halides with thermally induced reversible fluorescence transitions are promising smart optoelectronic materials. However, it is challenging to obtain such materials with reversible and fast fluorescent thermochromism at relatively low temperatures. Herein, two series of new zero-dimensional (0-D) hybrid perovskite indium chlorides doped with Sb3+ are synthesized and characterized, namely (TAEA)InCl6·Cl·4H2O: xSb3+ (1: xSb3+) and (TETA)InCl6·Cl·H2O: xSb3+ (2: xSb3+) (TAEA = quadruply protonated tris(aminoethyl)amine; TETA = quadruply protonated triethylenetetramine; x = 0 − 15 %). Compound 1: 0.5 %Sb3+ displays green broadband emission with photoluminescence quantum yield (PLQY) of 44.4 %, while compound 2: 1 %Sb3+ produces yellow emission with PLQY of 73.46 %. A reversible transition between green and orange light emission for 1: 0.5 %Sb3+ can be triggered by thermal stimulation; such photoluminescence (PL) color switching happens with a fast response time of 20 s and a low transition temperature of 333 K. In addition, the materials combining compounds 2: 1 %Sb3+ and 1: 0.5 %Sb3+ can achieve complex digital encryption and decryption upon heating. Furthermore, due to its excellent luminous efficiency, the 2: 1 %Sb3+ is employed as yellow phosphor for white light-emitting diode (WLED). The WLED shows a CRI of 90.5 and a CCT of 5415 K, superior to most WLEDs based on hybrid metal halides. Finally, the impact of forming the self-trapped excitons state and complex PL mechanism of compound 1: 0.5 %Sb3+ are investigated through DFT calculations and femtosecond transient absorption techniques. This work provides new insights into the design of hybrid metal halides with multiple optical properties, paving the way to obtaining materials for multiple optical applications.

Single-phase Ca3Sc2Ge3O12: Tb3+, Eu3+ phosphors with tunable photoluminescence and temperature sensing properties

A set of germanate garnet phosphors containing Tb3+ and Eu3+ were adequately synthesized using the high-temperature solid-state technique. The structural properties, photoluminescence characteristics, fluorescence lifetimes, and temperature-sensing capabilities of the phosphors were thoroughly investigated. X-ray diffraction confirms the crystalline structure of the phosphors, while photoluminescence spectra reveal a colour shift attributed to the transfer of energy from Tb3+ to Eu3+ as the concentration of Eu3+ increases. The phosphors excited by UV light display a transition in colour from green to yellow, and subsequently to red, which can be used as a colour tunable phosphor in white light-emitting diode (w-LED) applications. As a novel temperature sensing material, the maximum relative sensitivity of Ca3Sc2Ge3O12: Tb3+, Eu3+ phosphor is 0.1044 K–1 (298 K), highlighting its potential for applications in temperature sensing.

Atomic-level investigation of structure and formation process of Y3Al5O12 with super-high content of Ce emitting anomalous orange-red emissions

Ce-doped yttrium aluminum garnet (YAG:Ce, Y3Al5O12:Ce) is the most commonly used yellow phosphor in white light-emitting diodes. Recently, we found that (Y1–xCex)3Al5O12:Ce with a super-high content of Ce (x = 0.11–0.21) can be prepared by a polymerized complex method and exhibits anomalous orange–red emission. To understand the nature of this anomalous behavior from the atomic level, we applied high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and scanning transmission electron microscopy–energy dispersive X-ray spectroscopy (STEM-EDS), a state-of-the-art technique that enables analysis of the atomic-level elemental distributions of Al, Y, and Ce. STEM-EDS images on the atomic level were successfully obtained for YAG:Ce. It was found that Ce in Y site has spatially uneven for few nanometers. Ce–K edge extended X-ray absorption fine structure (EXAFS) analysis was also conducted, which revealed a high level of asymmetry around Ce. By combining the STEM-EDS and EXAFS results, a dynamic model for the red emission was proposed. STEM-EDS also revealed that CeO2 nanocrystals were firstly formed with low-temperature annealing and that the reaction of Y with the CeO2 nanocrystals subsequently yielded YAG:Ce, unlike in the conventional one-step high-temperature synthesis.

Thermally-stable and color-tunable novel single phase phosphor Ca2GaTaO6:Dy3+, Sm3+ for indoor lighting applications

This study successfully synthesized novel phosphors Ca2GaTaO6:xDy3+ (CGTO:xDy3+) and Ca2GaTaO6:0.06Dy3+, ySm3+ (CGTO:0.06Dy3+, ySm3+) using the high temperature solid-phase reaction preparation. The microstructure, optical properties, and energy transfer mechanism of the phosphors were studied through X-ray diffraction (XRD), scanning electron microscope (SEM), photoluminescence (PL) spectra and fluorescence lifetimes. XRD and corresponding refinement results indicate that Dy3+ and Sm3+ ions were effectively doped into the Ca2GaTaO6 (CGTO) lattice. The SEM graphs show that the elements in CGTO:0.06Dy3+, 0.5Sm3+ phosphors are uniformly distributed. PL spectra analysis show the CGTO:xDy3+ phosphors display two strong emission peaks located at 482 nm for blue emission and 575 nm for yellow emission when excited with 350 nm light. Under uniform conditions, when excited with 365 nm of light, the CGTO:0.06Dy3+, ySm3+ phosphors emit light that can be tuned with adjustable color coordinates and correlated color temperature (CCT) by incorporating varying proportions of Sm3+ ions. This tunability is achieved through the effective energy migration from Dy3+ to Sm3+ ions within the phosphor material. Furthermore, the emission spectra and weaken lifetimes of the CGTO:0.06Dy3+, ySm3+ confirm the energy transport between Dy3+ and Sm3+, and the energy transfer efficiency reached to 76 %. At 423 K, the luminescence intensity of CGTO:0.06Dy3+, 0.05Sm3+ phosphor retains 87 % of the intensity observed at 298 K, signifying its excellent thermal durability. Finally, the electroluminescent performance of the CGTO:0.06Dy3+ and CGTO:0.06Dy3+, 0.05Sm3+ phosphors packaged on 365 nm light-emitting diode (LED) chips respectively were studied to investigate the capability applications of the phosphors in white light-emitting diodes (WLEDs) field. The CCT of the packaged LEDs decline from 3396 to 2825 K, indicating CGTO:0.06Dy3+, 0.05Sm3+ phosphor shifts to warmer white light. At a voltage input of 3.4 V and a current of 600 mA, the thermal sensing shows that the WLEDs maintain aptitude for 90 min, showing that the packaged WLEDs can function consistently under elevated temperatures. These studies indicated the phosphors have potential applications in indoor lighting.

Vapor- and temperature-triggered reversible optical switching for multi-response Cu8 cluster supercrystals

Multi-response metal cluster supercrystal materials, which can simultaneously display various such as color, photoluminescence, changes by bearing only one stimulus, have huge potential as stimuli-responsive intelligent material, but are rarely reported. Here, we report three Cu8 cluster supercrystals, Cu8-1, Cu8-2, and Cu8-3, with homologous cluster molecule units [Cu8(PNP)3(EPPTA)6](PF6)2 but distinct packing. These supercrystals display bright μs-long photoluminescence with a high quantum yield of up to 26.6 % in solid-state at room temperature and aggregation-induced emission (AIE) characteristic. Superior thermal stability and blue-excitable bright yellow emission make Cu8-3 serve as a yellow phosphor for white light-emitting diode. Furthermore, upon being stimulated by solvent vapor and temperature, reversible supercrystal-to-supercrystal transformations can be witnessed accompanied by remarkable color and luminescence switching. This work not only provides a kind of Cu cluster supercrystal model but also motivates the further development of metal clusters in multi-response materials.

Microstructure, optical, and electrical characteristics of NaBaBi2(PO4)3: Sm3+ orange-red phosphor for WLEDs

White light-emitting diodes (WLEDs) are widely used as lighting devices in daily life. However, due to the scarcity of orange-red components, they lack warm white light. Therefore, there is an urgent need for orange-red phosphors to improve the lighting quality and generate more saturated and warm white light. In this regard, NaBaBi2(PO4)3: xSm3+ orange-red phosphors were synthesized using the solid-state method. A systematic study was conducted on the microstructure, optical, and electrical properties of NaBaBi2(PO4)3: xSm3+ phosphors through various characterizations such as X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, diffuse reflectance spectroscopy, photoluminescence spectroscopy, fluorescence decay curves, and electrochemical impedance spectroscopy. The diffuse reflectance spectrum indicates that with the increase of Sm3+ doping concentration, the optical bandgap decreases. Remarkably, the NaBaBi2(PO4)3: 0.05Sm3+ phosphor has good thermal stability, and its retention rate is 84.42% at a high temperature of 428 K. Furthermore, the packaged LED manifested desirable characteristics, such as a low correlated color temperature (CCT ∼ 4280 K) and a high color rendering index (CRI ∼ 82), as evidenced by rigorous testing. These results indicate that the NaBaBi2(PO4)3: Sm3+ phosphors have a significant potential for utilization in the LED lighting industry.

Electronic structure, colour-tunable emission and energy transfer in Li3Ba2Y3(WO4)8:Bi3+,Eu3+ phosphors for white light-emitting diodes.

Solid-state phosphor-converted white light-emitting diodes (pc-WLEDs) are the leading trend of the lighting industry in the 21st century. To pursue high quality WLED lighting, the development of highly efficient phosphors with tunable luminescence has become a hot research topic. Herein, we reported for the first time on Bi3+/Eu3+-doped Li3Ba2Y3(WO4)8 phosphors that exhibited tunable emission and high energy transfer efficiency of 89.90% from Bi3+ to Eu3+. The phase purity, microstructure, electronic structure and photoluminescence properties of these phosphors were studied in detail. Bi3+ and Eu3+ were effectively doped in Li3Ba2Y3(WO4)8 with an optical bandgap of 3.81 eV. The band structure and density of states were quantitatively evaluated by density functional theory simulation. At an excitation wavelength of 342 nm, the Bi3+-doped phosphor achieved yellow-green emission. By alloying Eu3+ into Li3Ba2Y3(WO4)8:Bi3+, the luminescence gradually turned red due to the energy transfer from Bi3+ to Eu3+. Moreover, the activation energy of the prepared phosphor was 0.1897 eV, demonstrating excellent thermal stability. Eventually, by combining Li3Ba2Y3(WO4)8:4%Bi3+,4%Eu3+ and a blue-emitting BAM:Eu2+ phosphor with a 365 nm ultraviolet chip, a WLED device with a high colour rendering index (Ra) of 78.7, chromaticity coordinates of (0.3401, 0.3131) and correlated colour temperature of 5080 K was successfully achieved. This work provided new insights into the design and development of color-tunable phosphors for white LEDs.

Crystal structure, Bi3+ yellow luminescence, and high quantum efficiency of Ba3SbAl3Ge2O14:Bi3+ phosphor for white light-emitting diodes

Bi3+ ions occupy Ba site to form one Bi3+ luminescent center, which is consistent with the trigonal structure of BSAG. This phosphor has a high quantum efficiency of 95.3% and can be used in WLEDs.

Ultra-broadband emission up to 181 nm of VO4-activated yellow phosphor for white light-emitting diodes with high color rendering index

Exploring broadband yellow phosphors capable of covering the cyan to red region is an effective approach to achieve high-performance phosphor-converted white light-emitting diodes (pc-WLEDs). Herein, we synthesized a series of VO4-activated ultra-broadband KSrP1−xVxO4 (0.1 ≤ x ≤ 1) yellow phosphors via high temperature solid-state reaction. Successive substitution of P5+ with V5+ causes a slight expansion of the lattice constant and induces several highly localized energy-levels within the forbidden band. Density functional theory calculations confirm that these newly appeared sharp-line energy-levels are attributed to the constructed VO4 anionic groups. With the optimized V5+ content, the KSrP0.7V0.3O4 phosphor exhibits an ultra-broadband yellow emission centered at 537 nm under 355 nm excitation. Impressively, its full width at half maximum is up to 181 nm, exceeding that of most reported counterparts. At 105 °C, the KSrP0.7V0.3O4 sample experiences an emission loss of 53%. A WLED device is fabricated by using phosphor blend of KSrP0.7V0.3O4 yellow phosphor and the commercial BaMgAl10O17: Eu2+ blue phosphor and a 355 nm NUV LED chip, demonstrating bright white emission with high color rendering index (CRI) of 90 and suitable correlated color temperature of 5953 K. These findings indicate that this phosphor has great potential for achieving high CRI WLEDs.

Synthesis and warm white emission performance of single-component Ca7Mg2(PO4)6:Dy3+, Eu3+ phosphor for white light-emitting diodes

A single-component Ca7Mg2(PO4)6:Dy3+, Eu3+ white-emitting phosphor was synthesized by a sol-gel approach. The effects of the amounts of Dy3+ ions and Eu3+ ions on the luminescence characteristics and crystal structure of Ca7Mg2(PO4)6:Dy3+, Eu3+ were systematically investigated. The Ca7Mg2(PO4)6:Dy3+, Eu3+ phosphors had a Ca7Mg2(PO4)6 structure with an R3c (161) space group. The Ca7Mg2(PO4)6:Dy3+ phosphor showed emission peaks at both 484 nm (blue) and 576 nm (yellow), which led to the realization of white light. Furthermore, after codoping Eu3+ ions into the structure, a red emission peak (∼617 nm) appeared in the spectrum as a supplementary red component. A warm white light with a low correlated colour temperature (CCT) is obtained from Dy3+/Eu3+-codoped Ca7Mg2(PO4)6. The luminescence intensity at 483 K still reaches more than 73 % of that at 303 K. The packaged LEDs display a bright warm white light with CCT value and colour rendering index (CRI) of 3878 K and 86.7, respectively, which is comfortable for the human eye. With excellent luminescence performances, the white-emitting Ca7Mg2(PO4)6:Dy3+, Eu3+ phosphor had a significant application potential in the w-LED field.

New green garnet-type phosphor LuMgAl5SiO12:Ce3+ for filling cyan gap to achieve full-spectrum and high colour-rendering-index white light-emitting diodes

Phosphors with simple preparation, high luminous efficiency and excellent thermal stability are highly desirable for commercial white light-emitting diodes (W-LED). In the paper, a new garnet-type green phosphor LuMgAl5SiO12:Ce3+ (LMASO:Ce3+) has been successfully prepared by a high-temperature solid-state reaction. The crystal structure and photoluminescence properties were investigated in detail. X-ray diffraction and the Rietveld refinement demonstrated the crystal structure of LMASO belongs to cubic systems with an Ia 3¯ d (230) space group. The unit cell parameters of LMASO:0.08Ce3+ phosphor were found to be a = 11.90418 Å and V = 1686.935 Å3. LMASO:Ce3+ phosphors have two excitation bands with peaks at 340 and 436 nm, attributed to the 4f → 5d transition of Ce3+ ions. Under excitation at 436 nm, LMASO:0.08Ce3+ phosphor exhibits a broad and asymmetric emission band in the 450–700 nm range. Notably, a W-LED device was created by combining a 455 nm blue LED chip with the obtained green sample and the commercially available red CaAlSiN3:Eu3+ phosphor. The device emitted a bright warm white light with a low correlated color temperature of 3584 K and a high color rendering index of 96.0 at a drive current of 40 mA. The article indicates that LMASO:Ce3+ samples can serve as a potential green phosphor for W-LEDs, and offers a new strategy for designing efficient phosphors.

A highly thermal-stable red-emitting tantalate phosphor for WLED and multiple-mode optical temperature sensor dual-applications

Recently, more and more attention has been concentrated on luminescence materials activated with rare-earth ions for white light-emitting diodes (WLEDs) or optical thermometers. However, due to their opposite requirements for thermal response, it is hard to realize the above dual applications in the same material. Herein, a red-emitting tantalate phosphor, Gd3TaO7:Eu3+, was designed and prepared to solve the problem. The emission of Eu3+ in the phosphor was surprisingly observed to be different from that in most of the reported red phosphors activated with Eu3+, that is, the emissions coming from the f - f transitions of Eu3+ exhibit severe splitting, and the intensities of several strong transitions are not very different. According to the structural and spectral analyses, the reasons may be the highly covalent and polarized lattice environments of Eu3+ in this material. When excited with 393 nm, the temperature-dependent photoluminescence (TDPL) of Gd3TaO7:Eu3+ presents a normal thermal quenching and the integrated intensity at 500 K keeps 90.8 % compared to that at 300 K. Whereas the TDPL presents an edge abnormal thermal quenching phenomenon upon the excitation of 330 nm. Taking advantage of the special TDPL characteristics, a WLED device and a multiple-mode optical thermometer are successfully realized in this material. The former has excellent performances with high Ra of 88.8 and low CCT of 3882 K, and the latter includes one type of excitation intensity ratio and two types of fluorescence intensity ratio with the maximal relative temperature sensitivities of 0.92 % K−1, 0.97 % K−1 and 0.92 % K−1, respectively. The results reveal that Gd3TaO7:Eu3+ phosphor has a great prospect in WLED and multiple-mode optical temperature sensor dual-applications, and this work may provide a new and effective strategy for developing multifunctional optical materials.

Anomalous 5D0→7F4 Transition of Eu3+‐Doped BaLaGaO4 Phosphors for WLEDs and Plant Growth Applications

AbstractEuropium (Eu3+) doped phosphors typically exhibit orange or red emission and are used in lighting and display applications, originating from the 5D0→7F1 and 5D0→7F2 transitions of Eu3+. However, BaLaGaO4: xEu3+ deep‐red phosphor, when excited by near‐ultraviolet light, is mainly 5D0→7F4 transition (703 nm). Meantime, the BaLaGaO4: 0.30Eu3+ exhibits a high I423K/I298K value of 71% and a high quantum yield of 82.54%. Furthermore, the prepared samples are mixed with commercial blue and green phosphors in a certain proportion to make white light‐emitting diodes (WLEDs). The color coordinate of the fabricated WLEDs is (0.3208, 0.3436), with a color rendering index of 91.9 and an R9 value of 73. Based on the unique spectral characteristics of this compound, a prototype device of a deep‐red LED with phosphor conversion is developed, which exhibits color coordinates (0.6294, 0.3581) and a color purity of 96.4%. The conducted germination experiments with plant seeds have provided compelling evidence regarding the considerable positive effects of the deep‐red LEDs on plant growth. These findings further emphasize the highly promising potential application of BaLaGaO4: Eu3+ deep‐red phosphor in WLEDs and plant growth lighting.

Efficient bright green phosphor for white light-emitting diode using in backlight application

The (Ba,Ca)ScO2F:Bi3+,K+ phosphor with narrow emission band and green emission color peaking at 510 nm is demonstrated in the study. This phosphor is prepared using a solid-state reaction at high temperatures. Based on characterizing data, the increasing concentration of Ca2+ induces the shrinkage of the unit cell and the narrower spacing, leading to the increase in the photoluminescence of the phosphor. This also cause a red shift in the emitting range from 504 nm to 510 nm. The phosphor shows good absorption peaking at 415 nm, matching the excitation wavelength of the used nearultraviolet (UV) light emitting diode (LED) chip. When being applied in a white light‐emitting diodes (WLED) with 4,000 K, the phosphor could increase the luminous flux as its doping concentration increase. Besides, the WLED doping (Ba, Ca) ScO2F: Bi3+, K+ shows emission regions in blue, green, and red wavelength bands. The data from the study indicates that the phosphor is potential for developing the white-LED for backlight purposes.