Cooperative cation substitution facilitated construction of garnet oxynitride MgY2Al3Si2O11N:Ce3+ for white LEDs

Structural modification is an important means to induce redshift of Ce³⁺ emission in garnet phosphor. We intend to design and synthesize garnet oxynitride compounds which combine attributes of rigidity inherited from garnet structure and of high covalence characteristic of oxynitride compounds. However, impurity phase usually occurs in the nitridation of garnet phosphor, due to the low solubility of nitrogen in oxides. We herein exploit the cooperative cation substitution strategy to facilitate the incorporation of nitrogen in Y₃Al₅O₁₂. It is found that partial substitution of Y³⁺‐Al_tet³⁺ pairs by Mg²⁺‐Si⁴⁺ pairs can diminish the phase instability caused by the replacement of Al_tet³⁺‐O^2? by Si⁴⁺‐N^3?. A novel pure garnet phase oxynitride phosphor MgY₂Al₃Si₂O₁₁N:Ce³⁺ with a higher substitution content of N has been obtained and the successful incorporation of N in the garnet phosphor is confirmed by the Rietveld refinements of XRD, XPS, and TEM. The emission and excitation spectra indicate that the blue‐light‐excitable MgY₂Al₃Si₂O₁₁N:Ce³⁺ phosphor exhibited a bright yellow‐orange emission peaking at 570 nm, which is redshifted by 28 nm when compared to YAG:Ce³⁺. The garnet oxynitride phosphor exhibit excellent thermal stability with high quantum efficiency and is a promising candidate for warm white LED.     

Multicolor Emission in a Single‐Phase Phosphor Ca3Al2O6:Ce3+,Li+: Luminescence and Site Occupancy

A single‐phase multicolor emitting phosphor, Ca₃Al₂O₆:Ce³⁺,Li⁺, was prepared by a solid‐state reaction. When the Ce³⁺ concentration is lower than 0.030 (molar ratio in Ca₃Al₂O₆), yellow and greenish blue emissions can be observed under the excitation by a blue and a near UV light, respectively. The yellow‐emitting phosphor possesses an internal quantum efficiency of 89%. Additional purplish blue emission turns up when Ce³⁺ concentrations are higher than 0.040. Tunable emission bands are originated from Ce³⁺ ions on different Ca sites in Ca₃Al₂O₆. Although the emission band of purplish blue or greenish blue overlaps the excitation band of yellow emission, and the distances between the unlike Ce³⁺ ions are in the range of electric dipole–dipole interaction, no energy transfer is observed. Furthermore, emission wavelengths for the yellow, greenish blue, and purplish blue emission show little change upon increasing Ce³⁺ concentrations.     

Broadband emission of single-phase Ca3Sc2Si3O12:Cr3+/Ln3+ (Ln = Nd,Yb, Ce) phosphors for novel solid-state light sources with visible to near-infrared light output

Novel single-component phosphors Ca₃Sc₂Si₃O₁₂:Cr³⁺/Ln³⁺ (CSS:Cr³⁺/Ln³⁺, Ln = Nd, Yb, Ce) with broadband near-infrared (NIR) emissions are synthesized. Their phase structure, photoluminescence properties and energy transfer between Cr³⁺ and Ln³⁺ ions are investigated. In the CSS host, Cr³⁺ ions occupy Sc³⁺ sites with low-field octahedral coordination, and thus show a broadband emission in 700–900 nm under the blue light excitation. Nd³⁺, Yb³⁺ and Ce³⁺ ions substitute Ca²⁺ sites in CSS, where Nd³⁺ and Yb³⁺ ions emit the NIR light in 900–1100 nm and their excitation efficiencies at ∼450 nm are greatly enhanced by utilizing the energy transfer from Cr³⁺ to Nd³⁺/Yb³⁺ ions. Ce³⁺ ions can further enhance the absorption of CSS:Cr³⁺/Ln³⁺ phosphors to the blue light, and at the same time contribute to the visible emission in 480–650 nm. Furthermore, CSS:Cr³⁺/Ln³⁺ phosphors show good thermal stability, and approximately 79% of the initial emission intensity is sustained at 150 °C. A phosphor-converted LED (pc-LED) prototype is fabricated by integrating the as-prepared phosphor CSS:Cr³⁺/Ln³⁺ and the commercial phosphor CaAlSiN₃:Eu²⁺ with the blue LED chip, showing a super broadband emission ranging from 450 to 1100 nm. This finding shows the potential application of CSS:Cr³⁺/Ln³⁺ phosphors in broadband NIR pc-LEDs or super broadband LED sources with visible to NIR light output.     

The electronic structure,site occupancy and luminescent properties of Ce3+-activated Li2Ca2Si2O7 blue phosphor

Rare earth activated lithium-containing alkaline earth silicates is an intensely studied topic in the fields of luminescent materials. In this study, a cerium-activated lithium-silicate blue phosphor, Li₂Ca₂Si₂O₇:Ce³⁺, was explored using structural computational simulations and systematic experiments. The Li₂Ca₂Si₂O₇:Ce³⁺ phosphor can be efficiently excited by near-ultraviolet and cathode ray light sources. According to the spectroscopic redshift theory, time-resolved photoluminescence (TRPL) and cathodoluminescence (CL) spectra, it is determined that the broad emission of Li₂Ca₂Si₂O₇:Ce³⁺ comes from two different luminescent centers. In addition, Li₂Ca₂Si₂O₇:Ce³⁺ exhibits strong blue emission at ~415 nm with high quantum yield and stable emission under high temperature and continuous electron beam bombardment. Therefore, this study provides a new insight into developing new high-efficiency and high-purity trichromatic phosphors.     

Discovery of new broadband yellow-emitting nitridoalumosilicate phosphor and its pc-WLED application

Developing a yellow phosphor with broadband emission covering more red-light areas is an effective approach to achieve high-quality solid-state lighting. In this study, a novel yellow-emitting nitride phosphor, Ca₅Si₂Al₂N₈:Ce³⁺, was successfully prepared at atmospheric pressure and lower temperatures (1300°C), and its structure-property relation was revealed using crystal refinement, photoluminescence (PL) spectra, time-resolved PL spectra, and density-functional theory calculations. The results demonstrate that Ca atoms occupy three different crystallographic sites in the lattice, which are substituted by Ce³⁺ to form multiple luminescence centers. Thus, Ca₅Si₂Al₂N₈:Ce³⁺ emits strong yellow light with a maximum peak at 585 nm and a wide emission band. Compared with YAG:Ce³⁺, Ca₅Si₂Al₂N₈:Ce³⁺ has a wider emission band with a FWHM of 150 nm, which can effectively cover the green and red areas. Moreover, the sample can be fully excited by a blue LED chip due to its broad excitation band. Notably, the Ca₅Si₂Al₂N₈'s tight crystal structure composed of edge-sharing AlN₄ and SiN₄ tetrahedra pairs guarantee its thermochemical stability and quantum efficiency. Furthermore, Ca₅Si₂Al₂N₈:Ce³⁺ exhibits better thermal stability than YAG:Ce³⁺. The results indicate that Ca₅Si₂Al₂N₈:Ce³⁺ is a promising yellow phosphor for WLEDs.     

Preparation and Application of Strong Near‐Infrared Emission Phosphor Sr3SiO5:Ce3+,Al3+,Nd3+

This work investigated the near‐infrared (NIR) emission properties of mCe³⁺, xNd³⁺ codoped Sr_3?m?x(Si_1?m?xAl_m+x)O₅ phosphors. Samples with various doping concentrations were synthesized by the high‐temperature solid‐state reaction. Al³⁺ ions have the ability to promote Ce³⁺ ions to enter into the Sr²⁺ sites and to improve the visible emission of Ce³⁺. Thus the NIR emission of Nd³⁺ is enhanced by the energy‐transfer process, which occurred from Ce³⁺ to Nd³⁺. The device based on these NIR emission phosphors is fabricated and combined with a commercial c‐Si solar cell for performance testing. Short‐circuit current density of the solar cell is increased by 7.7%. Results of this work suggest that the Sr_2.95Si_0.95Al_0.05O₅:0.025Ce³⁺, 0.025Nd³⁺ phosphors can be used as spectral convertors to improve the efficiency of c‐Si solar cell.     

Production and optical properties of Ce3+-activated and Lu3+-stabilized transparent gadolinium aluminate garnet ceramics

We first report the novel Ce³⁺-activated and Lu³⁺-stabilized gadolinium aluminate garnet (GAG) transparent ceramics derived from their precipitation precursors via a facile co-precipitation strategy using ammonium hydrogen carbonate (AHC) as the precipitant. The resulting precursors in liquid phase were substantially homogeneous solid solutions and could directly convert into sinterable garnet powders via pyrolysis. Substituting 35 at.% of Lu³⁺ for Gd³⁺ was effective to stabilize the cubic GAG garnet structure and transparent (Gd,Lu)₃Al₅O₁₂:Ce ceramics were successfully fabricated by vacuum sintering at 1715°C. The ceramic transparency was improved by optimizing the particle processing conditions and the best sample had an in-line transmittance of ~70% at 580 nm (Ce³⁺ emission center) and over 80% in partial infrared region with a fine average grain size of ~4.5 μm. Transparent (Gd,Lu)₃Al₅O₁₂:Ce ceramics have a short critical wavelength (<200 nm) and a maximal infrared cut-off at ~6.6 μm. Both the (Gd,Lu)₃Al₅O₁₂:Ce phosphor powder and the transparent ceramic exhibited characteristic yellow emission of Ce³⁺ with strong broad emission bands from 490 to 750 nm upon UV excitation into two groups of broad bands around 340 and 470 nm. The photoluminescence and photoluminescence excitation intensities as well as the quantum yield were greatly enhanced via high-temperature densification. Both the phosphor powder and ceramic bulk had short effective fluorescence lifetimes.     

Luminescence Properties and Energy Transfer of Ce3+,Tb3+‐Coactivatedβ‐SiAlON Phosphors

Using the solid‐state reaction method, Ce³⁺,Tb³⁺‐coactivated Si₅AlON₇ (Si_6?zAl_zO_zN_8?z, z = 1) phosphors were successfully synthesized. The obtained phosphors exhibit high absorption and strong excitation bands in the wavelength range of 240–440 nm, matching well with the light emitting‐diode (LED) chip. The ET from Ce³⁺ to Tb³⁺ ions in Si₅AlON₇:Ce³⁺,Tb³⁺ has been studied and demonstrated by the luminescence spectra and decay curves. Moreover, the phosphors show tunable emissions from blue to green by tuning the relative ratio of the Ce³⁺ to Tb³⁺ ions. Thermal quenching properties of Si₅AlON₇:Ce³⁺,Tb³⁺ had also been investigated and the quenching temperature is ~190°C. These results show that Si₅AlON₇:Ce³⁺,Tb³⁺ could be a promising candidate for a single‐phased color‐tunable phosphor applied in UV‐chip pumped LEDs.     

A low cost and high efficient Ba9(Lu2-x-yAlx)Si6O24:yCe3+ cyan-emitting phosphor

White LEDs constructed by near-ultraviolet chips and red/green/blue/cyan-emitting phosphors are an important route for healthy lighting. However, efficient cyan-emitting phosphors are quite scarcity. The cyan-emitting phosphor Ba₉Lu_1.5Al_0.5Si₆O₂₄:Ce³⁺ (BLASO:Ce³⁺) was reported for the first time. Under 400 nm excitation, BLASO:Ce³⁺ shows a emission peak at 488 nm with an FWHM of about 117 nm. At room temperature, the internal quantum efficiency (IQE) can reach as high as 90.8%. At 150 °C, the IQE decreases to 81.5%, indicating an excellent thermal stability. The effect of the Al substitution for Lu on crystal structures and photoluminescence were investigated. The homogeneity of the luminescence was diagnosed by viewing microscopic particles based on the scanning electron microscope (SEM) equipped a cathodoluminescence (CL) system.     

Efficient Near‐Infrared Emission of Ce3+–Nd3+ CoDoped (Sr0.6Ca0.4)3(Al0.6Si0.4)O4.4F0.6 Phosphors for c‐Si Solar Cell

Ce³⁺, Nd³⁺ codoped (Sr_0.6Ca_0.4)₃(Al_0.6Si_0.4)O_4.4F_0.6 phosphors were synthesized through the high‐temperature solid‐state reaction method. Luminescence spectra, absorption spectra, and decay lifetimes of these samples have been measured to prove the energy‐transfer process from Ce³⁺ to Nd³⁺. Under UV and blue light excitation, (Sr_0.6Ca_0.4)₃(Al_0.6Si_0.4)O_4.4F_0.6:Ce³⁺,Nd³⁺ phosphors exhibit near‐infrared (NIR) emission, mainly peaking at 1093 nm and secondarily at 916 nm. The NIR emission matches well with the band gap of c‐Si. Results of this work suggest that the (Sr_0.6Ca_0.4)₃(Al_0.6Si_0.4)O_4.4F_0.6:Ce³⁺, Nd³⁺ phosphors have potential application as down‐shifting luminescent convertor for enhancing the photoelectric conversion efficiency of c‐Si solar cell.     

Structure and Photoluminescence of A Blue‐Green‐Emitting Phosphor for Near‐UV White LEDs

A series of phosphors Ca_12(0.97?x)Al₁₄O₃₂F₂: 0.03Ce³⁺, xTb³⁺ have been prepared by a hightemperature solid‐state reaction using boric acid as flux. These oxyfluorides crystallize in cubic structure, space group. Under the near ultraviolet excitation within wavelength range 310–390 nm, Ca_12(0.97?x)Al₁₄O₃₂F₂: 0.03Ce³⁺, xTb³⁺ phosphors exhibit an intense emission covering a broad band of 370–500 nm derived from the 5d→4f transitions of Ce³⁺ and a characteristic emission at 544 nm of Tb³⁺. The emission can be tuned from blue to green by altering the relative ratio of Ce³⁺ to Tb³⁺ in the composition. The energy‐transfer mechanism from Ce³⁺ to Tb³⁺ is investigated based on the site occupancy of the luminescence center in the crystal structure of the Ca₁₂Al₁₄O₃₂F₂ host. More importantly, when a certain amount of boric acid is added as flux in the synthesis, the fluorescence intensity of the phosphors increases about 65%. Because of its broad excitation and efficiently tunable blue to green luminescence, the Ca_12(0.97?x)Al₁₄O₃₂F₂: 0.03Ce³⁺, xTb³⁺ phosphors may find promising application as a near UV‐convertible phosphor for white‐light‐emitting diodes.     

Highly efficient yellow-orange emission and superior thermal stability of Ba2YAl3Si2O12:Ce3+ for high-power solid lighting

With great economic benefits, white LEDs (w-LEDs) have aroused worldwide attention. For phosphor-converted w-LED, highly efficient emission and good thermal stability of phosphor are significant parameters in practical application. Here, a yellow-orange garnet-structural phosphor, Ba₂YAl₃Si₂O₁₂:xCe³⁺ (x = 0-0.1) (BYAS:xCe³⁺) was developed by solid solution design. The broad emission spectrum of the as-synthesized phosphor could guarantee the effective increase of the color rendering index when it is combined with the InGaN blue chip. Benefiting from the garnet-type highly rigid framework, BYAS:xCe³⁺ exhibits an excellent thermal stability (50%@673K of the initial integrated intensity at 280 K) as well as high absolute quantum efficiency (80.4%@460 nm excitation light). Utilizing the approach of “phosphor-in-glass” (PiG), a high-power warm w-LED is achieved based on a blue LED plus PiG and the illuminance of this w-LED device can be as high as 4227 lx.     

Optimization of Ce3+ concentration and Y4MgSi3O13 phase in Mg2+-Si4+ Co-doped Ce: YAG ceramic phosphors

As a promising replacement for nitride red phosphors, Ce: Y₃(Mg_1.8Al_1.4Si_1.8)O₁₂ (Ce: YMASG) ceramic phosphors have attracted significant attention recently for their advantages in inorganic encapsulation and massive red-shifting of Ce³⁺ emission. In this work, Ce: YMASG with different doping concentrations of Ce³⁺ and Al₂O₃, was fabricated by vacuum sintering to investigate its effects on the elimination of the impurity phase and the enhancement of the luminescent properties of white light-emitting diodes (w-LEDs). It was discovered that the emission wavelength redshifts from 592 to 606 nm as the Ce³⁺ concentration increases, while at 450 K, the emission intensity deteriorates from 0.47 to 0.36 of its initial value. The Rietveld analysis revealed the presence of an impurity phase of Y₄MgSi₃O₁₃ with a concentration of 17.021 wt% in Ce: YMASG. With the introduction of Al₂O₃, the impurity phase was eliminated from the matrix completely, the emission peak shifted to a shorter wavelength, and the thermal stability was greatly improved. When the correlated color temperature was controlled at around 3000 K in the packaged w-LEDs, the commission international de l'éclairage (CIE) chromaticity coordinates shifted toward the bottom left corner of the diagram with increasing concentration of Ce³⁺. Conversely, the luminous efficiency (LE) increased from 36 lm/W to 58.6 lm/W as the concentration of Al₂O₃ increased from 0 to 10 wt%, which demonstrated the application prospect of the fabricated phosphor in warm w-LEDs.     

Effect of Boron Nitride (BN) on Luminescent Properties of Y3Al5O12:Ce Phosphors and their White Light‐Emitting Diode Characteristics

This article reports a low‐cost yellow‐emitting Y₃Al_5‐xB_xO_12‐xN_x:Ce³⁺ phosphor with an enhanced luminescent intensity and excellent thermal stability for white light‐emitting diodes (LEDs). It was synthesized by a simple gas‐pressure sintering (GPS) process. The effect of B³⁺–N^3? incorporation on the optical properties of Y₃Al₅O₁₂:Ce³⁺ phosphor was investigated. The addition of appropriate amounts of boron nitride (BN) leads to a marked increase in photoluminescent intensity and a slight shift of its emission spectra toward the blue region, which is assigned to the improved crystallinity and increased particle size. Especially, the prepared oxynitride phosphor does not exhibit any thermal quenching under high temperature, and the emission intensity at 250°C even increases up to 175% of that measured at 20°C. Finally, the white LED flat lamp with luminous efficiency as high as 101 lm/W, color rendering index of 72, and correlated color temperature of about 6600 K is successfully realized by using YAG:Ce³⁺ phosphor doped with 0.5 molar ratio BN, which is acceptable and promising for general indoor illuminations to replace fluorescent or incandescent lamps.     

Crystal structure,energy transfer mechanism and tunable luminescence in Ce3+/Dy3+ co-activated Ca20Mg3Al26Si3O68 nanophosphors

Ce³⁺, Dy³⁺ and Ce³⁺/Dy³⁺ co-doped Ca₂₀Mg₃Al₂₆Si₃O₆₈ (CMAS) nanophosphors were synthesized via modified solution-combustion method. Sharp X-ray diffraction patterns confirmed the formation of pure crystalline phase of Ca₂₀Al₂₆Mg₃Si₃O₆₈ as an orthorhombic crystal system having space group Pmmn. The phase purity of as synthesized material has allowed reliable structural parameters to be obtained from the Rietveld analysis of its powder diffraction pattern. The Ce³⁺, Dy³⁺ and Ce³⁺/Dy³⁺ emission at different lattice sites in CMAS host has been identified and discussed. Under ultra-violet (UV) excitation, optical properties and the energy transfer mechanism from Ce³⁺ to Dy³⁺ in CMAS: Ce³⁺/Dy³⁺ nanophosphors have been elaborated by photoluminescence spectroscopy. Also, the effects of doping and sintering temperature on the structure of prepared CMAS host samples have been investigated in detail. The Ce³⁺/Dy³⁺ concentration quenching mechanism due to multipole–multipole interaction has been studied and the critical energy-transfer distance was calculated to be 7.8 Å. The band gap of the synthesized phosphors was calculated from diffuse reflectance spectra using the Kubelka–Munk function. A uniform layered structure network has been revealed in scanning electron microscopy images of the CMAS phosphor. Transmission electron microscopy results indicate nanocrystalline nature of synthesized phosphors. CMAS: 1 m% Ce³⁺ and CMAS: 0.5 m% Dy³⁺ nano-luminescent powders are promising candidate as a blue and blue–yellow emitting UV convertible phosphor for application in white light emitting diodes. By utilizing the energy transfer mechanism in present CMAS: Ce³⁺/Dy³⁺ nanophosphors, with an appropriate tuning of the activator content, these phosphors can exhibit great potential for white light emission, as single-emitting component phosphors in solid state lighting technology.     

Green emitting Ba1.5Lu1.5Al3.5Si1.5O12: Ce3+ phosphor with high thermal emission stability for warm WLEDs and FEDs

By hetero-valence substituting Ba²⁺-Si⁴⁺ for Lu³⁺-Al³⁺ pair in Lu₃Al₅O₁₂: Ce³⁺, a new green phosphor Ba_1.5Lu_1.5Al_3.5Si_1.5O₁₂: Ce³⁺ (BLAS: Ce³⁺) has been obtained. It crystallizes in garnet structure with space group Ia-3d (230). In the structure, Ba²⁺ ions are incorporated into both dodecahedral Lu³⁺ and octahedral Al³⁺ sites while Si⁴⁺ ions only occupy tetrahedral Al³⁺ sites. Under the blue light irradiation of 450 nm, an intense green light peaking at 520 nm was observed and the PL spectrum can be fitted in two Gaussian components, due to the crystal field splitting of Ce³⁺ 5d states under D₂ symmetry constrains. The optical doping concentration of BLAS: Ce³⁺ is 6% mol, of which the IQE and EQE are 89.1% and 51.8%, respectively. Furthermore, this sample exhibits an extremely good thermal stability, i.e. the integrated emission intensity is still more than 90% of the initial intensity at 480 K. Then, a w-LED device was fabricated from this new green phosphor BLAS: Ce³⁺ and commercial red phosphor (Ca,Sr)AlSiN₃: Eu²⁺, which shows a quite high color rendering (Ra = 88.2) and a relatively low color temperature 4772 K. Besides, the phosphor exhibits a stable chromaticity under different acceleration voltages. The phosphor may be promising material for the development of solid-state lighting and display systems.     

Site engineering of Ce3+-doped calcium scandate phosphors and understanding of relevant red-shifted emitting from green to yellow

CaSc₂O₄:Ce³⁺ is a well-known green emitting phosphor, but needs to match with suitable red emitting phosphors in practical white lighting. Herein, a site engineering strategy is proposed to modify the local coordination environment of Ce³⁺ by introducing Y³⁺ and Mg²⁺ ions into the CaSc₂O₄ crystal lattice. The obtained results indicate in the modified Ce³⁺-doped samples (CSO-YMg), Y³⁺ ions can occupy both Sc³⁺ and Ca²⁺ sites simultaneously, and the Y³⁺ ions tend to occupy Ca²⁺ sites in low-doped stage and enter into the Sc³⁺ sites in the high-doped stage. The introduction of Y³⁺ ions gives rise to the existence of MgO in as-prepared CSO-YMg samples, and it can be effectively washed through pickling. In the spectral aspect, with the increase of Y³⁺ and Mg²⁺ ions, the main emission peak is red-shifted from 512 nm to 530 nm upon excitation at 450 nm. However, the high-doped sample presents much stronger thermally induced fluorescence quenching than CaSc₂O₄:Ce³⁺. The lattice defects caused by doped ions (Y³⁺ and Mg²⁺) and the non-radiative energy transfer process between the Ca²⁺ (Ce³⁺) and Sc³⁺ (Ce³⁺ or Ce⁴⁺) sites should be responsible for such evident quenching phenomenon in CSO-YMg, which is obviously different from the emitting feature of CaSc₂O₄:Ce³⁺ (only at Ca²⁺ sites). Besides, utilizing the as-prepared CSO-5 phosphors and a blue LED (~450 nm), a WLED was successfully fabricated, yielding a comparable performance to those with commercial Y₃Al₅O₁₂:Ce³⁺ phosphors. What discussed in this study would bring some inspirations in the exploration and understanding of Ce³⁺-based phosphors according to local structural modification.     

A Single‐Phased Sr1−y‐3x/2Al2Si2O8: xCe3+, yMn2+ with Efficient Energy Transfer as a Potential Phosphor for White‐Light‐Emitting Diodes

A series of Ce³⁺‐ and Mn²⁺‐(co‐)activated SrAl₂Si₂O₈ phosphors have been prepared at 1350°C under a reducing atmosphere and their photoluminescence properties have been studied as a function of the (co‐)dopant ions concentrations. We have discovered that energy transfer (ET) not only from Ce³⁺ to Mn²⁺ but also from “defects” to Mn²⁺ by the facts that there is existing significant overlap between the emission spectrum of Ce³⁺ (“defects”) and the excitation spectrum of Mn²⁺. The source of the “defects” in the host lattice is originated from the different charge substitution between Ce³⁺ and Sr²⁺. By adopting the principle of ET, the material SrAl₂Si₂O₈: Ce, Mn can act as a phosphor for white‐light ultraviolet light‐emitting diodes (UV‐LEDs) by tuning of the dopants contents.     

Overcoming the cyan gap for full-spectrum lighting using cation-substitution-induced rigid Ca2YZr2Al3O12:Ce3+

Mixing multicolor phosphors for simulating the full spectrum of sunlight illumination is a popular solution to obtain high-quality white light. However, there is still a need to overcome the cyan gap in the emission spectrum. In this work, a series of garnet Ca₂Y_0.94–xLu_xZr_2–yHf_yAl₃O₁₂:6%Ce³⁺ (abbreviated as CY_0.94–xLu_xZr_2–yHf_yA:Ce³⁺) cyan phosphors are designed and prepared by substituting Y³⁺ and Zr⁴⁺ in Ca₂YZr₂Al₃O₁₂:6%Ce³⁺ with Lu³⁺ and Hf⁴⁺ with smaller ionic radius and larger mass. Under 405 nm violet light excitation, the optimized Ca₂Y_0.88Lu_0.06Hf₂Al₃O₁₂:6%Ce³⁺ (CY_0.88Lu_0.06Hf₂A:Ce³⁺) shows a bright cyan emission band in the range of 430–750 nm with the peak at 477 nm. Importantly, the emission intensity and thermal stability properties of CY_0.88Lu_0.06Hf₂A:Ce³⁺ were significantly improved by 58% and 47% compared to those of pure Ca₂YZr₂Al₃O₁₂:Ce³⁺. Small and heavy cation substitution could induce highly stable rigid structure, thus enhancing emission intensity and stability. The color rendering index increases from 84.5 to 92.0 after supplementing CY_0.88Lu_0.06Hf₂A:Ce³⁺ phosphor in white light-emitting diode devices combining commercial red, green, and blue phosphors with a violet chip, indicating its practical application in full-spectrum lighting. The present study provides promising strategies for the design and development of efficient cyan materials for high-quality full visible spectrum light-emitting diode lighting.     

Ce3+‐ and Dy3+‐Doped Oxyfluoride Borosilicate Glasses with Near White Luminescence

A series of Ce³⁺/Dy³⁺‐doped oxyfluoride borosilicate glasses prepared by melt‐quenching method are investigated for light‐emitting diodes applications. These glasses are studied via X‐ray diffraction (XRD), optical absorption, photoluminescence (PL), color coordinate, and Fourier transform infrared (FT‐IR) spectra. We find that the absorption and emission bands of Ce³⁺ ions move to the longer wavelengths with increasing Ce³⁺ concentrations and decreasing B₂O₃ and Al₂O₃ contents in the glass compositions. We also discover the emission behavior of Ce³⁺ ions is dependent on the excitation wavelengths. The glass structure variations with changing glass compositions are examined using the FT‐IR spectra. The influence of glass network structure on the luminescence of Ce³⁺/Dy³⁺ codoped glasses is studied. Furthermore, the near‐ideal white light emission (color coordinate x = 0.32, y = 0.32) from the Ce³⁺/Dy³⁺ codoped glasses excited at 350 nm UV light is realized.