Commercial Phosphor Research Articles

Limited energy migration and circumscribed multiphonon relaxation produced non-concentration quenching in a novel dazzling red-emitting phosphor.

White LED applications are still constrained by extremely efficient narrow band red emitting phosphors. Meanwhile, the concentration quenching induced by energy migration is the main reason that limits the emission intensity of a red emitting phosphor. Therefore, developing a novel red emitting material with energy migration limitations seems necessary. Here, we proposed and realized the non-concentration quenching doping of Eu3+ ions in a Sr9Y2-2xW4O24:xEu3+ (0 ≤ x ≤ 1.0) phosphor for the first time by means of host preferential selection. By clearly investigating the crystal structure and luminescence kinetics, the long-distance between the nearby Eu3+ ions and the low phonon energy are the main reasons that suppress the energy migration and the cross-relaxation among Eu3+ ions. These advantages result in a high internal (90.47%) and external quantum efficiency (42.1%) of Sr9Eu2W4O24. With the help of the Judd-Ofelt theory and the large value of oscillator strength Ω2, Eu3+ ions are verified to occupy the non-symmetric lattice site with high color purity (94.4%). In addition, only 5.2% emission intensity loss at 140 °C can guarantee its application in LED devices. Moreover, the SYWO:Eu3+ phosphor has high thermal tolerance, high color stability, excellent moisture resistance and superior physical/chemical stability, and thus has broad practical spectral application prospects. The prepared WLED shows superior performance, and the calculated NTSC values are as high as 101.8% and 104.7%, respectively. For comparison, the optical performances of the Sr9Y2W4O24:Eu3+ phosphor outperform those of the standard commercial red phosphors, Y2O3:Eu3+ and Y2O2S:Eu3+, and almost match that of K2MnF6. These results may pave the way for fresh approaches to the study of high-performance Eu3+-activated phosphors.

U-type π-conjugated phosphorescent ligand sensitized lanthanide metal-organic frameworks for efficient white-light-emitting diodes.

Lanthanide metal-organic framework (Ln-MOF) based phosphors for light-emitting diodes (LEDs) play an important role in the fields of solid-state lighting and display. The rational design of organic antennae to address the drawback of low extinction coefficients of the lanthanide ions is highly desired. In this work, we provide a new design strategy to achieve an energy transfer molecule with a through-space conjugated folded structure, which can strengthen the skeleton rigidity and facilitate triplet state energy transfer. Consequently, one U-type π-conjugated molecule 2,6-bis(3,5-dicarboxylphenoxy) pyridine (H4L) was selected as a light gatherer to sensitize lanthanide ions for the construction of Ln-MOFs [Ln(HL)(H2O)3]n (Eu-MOF and Tb-MOF), which exhibit a long-lived luminescence lifetime (0.88 ms for Eu-MOF and 1.31 ms for Tb-MOF) and high quantum yields (50.87% for Eu-MOF and 85.64% for Tb-MOF). Furthermore, a white LED device with a colour rendering index (89) was fabricated using the mixture of Ln-MOFs with a commercial blue phosphor.

Competitive sensitization effect towards Luminescence-tuned Lanthanide-doped TiO2/SiO2 Core-shell nanoparticles for enhanced responsivity oxygen detection

The luminescence of TiO2 doped with Sm3+ can be excited through TiO2 band-to-band absorption, which exhibits oxygen sensitivity. However, its carrier behaviors and oxygen sensing mechanism have not yet been clarified, which inhibits the further improvement of sensitivity. In this study, using Eu3+ ions as an “energy level probe,” we demonstrated a novel strategy using a C@SiO2:2%Sm3+@TiO2 hollow double-shell nanostructure containing surface oxygen vacancies, designated a competitive sensitization effect for the first time. Density-functional theory combined with the experimental results revealed the carrier behaviors and oxygen sensing mechanism. Further, we demonstrated that the charge state of oxygen vacancies is controlled by the adsorption and desorption of dioxygen molecules, which affects electron relaxation and indirectly affects the luminescent behaviors. The effective exploitation of the competitive sensitization effect and revelation of the oxygen sensing mechanism ensured that the excitation of Sm3+ in C@SiO2:2%Sm3+@TiO2 can be controlled by the ambient oxygen concentration. Therefore, compared to the widely reported Sm3+-doped TiO2, C@SiO2:2%Sm3+@TiO2 demonstrated increased oxygen sensitivity (by over three folds) with a detection minimum of sub-100 ppm. Moreover, as ambient oxygen concentration changes, the luminescence color of the films prepared by using C@SiO2:2%Sm3+@TiO2 and commercial blue phosphors changes significantly (from pink to blue).

Discovery of a novel yellow-orange-emitting low oxygen nitride phosphor Lu6.254Si11N20.762O0.238:Ce3+ for white LED

A novel broadband orange emitting phosphor Lu6.254Si11N20.762O0.238:Ce3+ was prepared via solid state reaction from the series of compounds R6+x/3Si11N20+xO1-x (R = Y and Gd→Lu, x = 1 or 0.762). The results of TEM, XRD and refinements verified the phase purity and crystal structure and also indicated that Ce3+ was successfully integrated into the main lattice to replace the Lu3+ ions. The phosphor Lu6.254Si11N20.762O0.238:Ce3+ presents a broadband bright orange emission peaking at 556 nm with a full width at half-maximum (FWHM) of 110 nm. The unique photoluminescence properties arise from the fact that Ce3+ occupies three different crystallographic sites, which is verified by spectral Gaussian fitting and three-exponential fluorescence decay curves. The PL emission intensity at 150 °C maintained 54.2% of that at room temperature (25 °C), the relatively poor thermal stability of this phosphor may be determined to the octahedrals [LuO6]1, [Lu(O/N)6]2 and [Lu(O/N)7]3 are connected each other so closing, which enhances the nonradiation transition. A w-LED device with CCT (5100 K) and high CRI (96.5) was fabricated by combining commercial blue phosphor SPOCl:Eu2+, green phosphor BSSO:Eu2+, red phosphor SCASN:Eu2+ and LSNO:0.24Ce3+ phosphor with 410 nm n-UV LED. Thus, this work provide an low oxygen nitride phosphor for application in high color rendering and full-spectrum warm white lighting.

Mn4+ activated dodec-fluoride red phosphor Na3Li3In2F12:Mn4+ with excellent waterproof stability for WLEDs

Mn4+ activated fluoride red phosphors, as candidate red materials in white light-emitting diodes (WLEDs), have received widespread attention. However, the poor water stability limits their application. Herein, a novel dodec-fluoride red phosphor Na3Li3In2F12:Mn4+ with good waterproof stability was successfully synthesized by solvothermal method. The crystal structure, optical property, micro-morphology, element composition, waterproof property and thermal behavior of Na3Li3In2F12:Mn4+ phosphor were analyzed. Under the 468 nm blue light excitation, the Na3Li3In2F12:Mn4+ phosphor has narrow emission bands in the area of 590–680 nm. Compared with commercial red phosphor K2SiF6:Mn4+, the Na3Li3In2F12:Mn4+ phosphor possesses better waterproof stability. When soaked in water for 360 min, the PL intensity of the Na3Li3In2F12:Mn4+ phosphor remains at initial 80%. Finally, warm WLEDs with CRI of 87 and CCT of 3386 K have been fabricated using blue InGaN chip, YAG:Ce3+ yellow phosphor and Na3Li3In2F12:Mn4+ red phosphor.

Design of Eu2+‐activated broadband orange‐emitting phosphors with excellent luminescent performance for warm WLEDs

AbstractWe report orange‐emitting Sr8La0.5Na0.5Mg1.5(PO4)7:Eu2+ (SLNMPO‐0.5:Eu2+) and Sr7LaNaMg1.5(PO4)7:Eu2+ (SLNMPO‐1:Eu2+) phosphors with broad emission bands covering from 450 to 800 nm. The phosphors can be excited by n‐ultraviolet and blue light efficiently. Their crystal structure, diffuse reflection spectra, photoluminescence (PL) spectra, fluorescence decay curves and thermal stability were investigated systematically. Under the excitation of 365 and 400 nm, SLNMPO‐0.5:Eu2+ and SLNMPO‐1:Eu2+ both exhibit better PL properties and contain more red emissions than SMPO:Eu2+. CIE coordinates of SLNMPO‐0.5:Eu2+ and SLNMPO‐1:Eu2+ under 365 nm excitation are (0.460, 0.497) and (0.457, 0.494), respectively. Furthermore, high‐quality warm white light can be generated by fabricating warm white light‐emitting diode (WLED) devices with 370 nm LED chips, BaMgAl10O17:Eu2+ commercial blue phosphor and orange‐emitting SLNMPO‐0.5:Eu2+ (or SLNMPO‐1:Eu2+) phosphor. The correlated color temperature, Ra and color coordinates are 3880 K, 94.05, (0.3895, 0.3922) and 3736 K, 91.73, (0.4005, 0.4078) for the fabricated WLED devices with SLNMPO‐0.5:Eu2+ and SLNMPO‐1:Eu2+, respectively. The excellent performances indicate that SLNMPO‐0.5:Eu2+ and SLNMPO‐1:Eu2+ have great potential to be attractive candidates in the application of warm WLEDs.

Versatile phosphor-in-glass based on Sn–F–P–O matrix with ultra-high color rendering for white LEDs/LDs

White light with excellent color rendering property has been highly required for comfortable and healthy illumination. A facile strategy to achieve high color rendering index (Ra >90) in practical applications is using near ultraviolet chips as excitation sources combined with RGB phosphors. However, achieving high color rendering with both blue chips and near-ultraviolet (NUV) chips for commercial phosphors dispersed in phosphor-in-glass (PiGs) materials is still a big challenge. In this work, the PiG based on the ultra-low melting point Sn–F–P–O glass with commercial green (Lu3Al5O12:Ce3+) and red (SrxCa1-xAlSiN3:Eu2+) phosphors has been successfully fabricated by one-step sintering method. The phase identification and distribution of monochromatic red phosphor in glass (R-PiG) and green phosphor in glass (G-PiG) were investigated in detail. The Sn2+ ions in Sn–F–P–O matrix show the intense blue emission bands centered at 420 nm under the excitation of NUV chips (365 nm). Notably, the polychromatic red/green phosphor in glasses (R/G-PiGs) are versatile and exhibited excellent color rendering (Ra = 93, Ra = 95, Ra = 92, respectively) properties excited by both blue chips, NUV chips and laser diodes (WLD). The working temperature of R/G-PiGs is stable at ∼33 °C and ∼55 °C when employed in WLEDs/WLDs (1 W), which greatly prevented the phenomenon of “thermal quenching” for the phosphors caused by high temperature. Thus, the versatile R/G-PiG with ultra-high color rendering and excellent thermal properties indicates its promising application in high-power white LEDs/LDs.

Synthesis and optical properties of Mn4+ activated double-perovskite niobate deep red phosphors for WLEDs and plant cultivation

Mn 4+ doped oxides red phosphors have great potential for white-light-emitting diodes (WLEDs) and plant growth light. Herein, deep red phosphors Ba 2 LuNbO 6 :xMn 4+ with perovskite structure were synthesized by solid state method in air atmosphere. The crystal structure, morphology, composition and optical properties of Ba 2 LuNbO 6 :Mn 4+ phosphors were systematically studied by X-ray diffraction, Rietveld refinement, SEM and EDS and photoluminescence spectra. Under excitation by 380 nm NUV light, the phosphor emitted bright red light around 670 nm and far-red light around 697 nm owing to the spin-forbidden 2 E g → 4 A 2g transition of Mn 4+ ions. Temperature-dependent photoluminescence spectra confirmed the high thermal stability of Mn 4+ -activated Ba 2 LuNbO 6 phosphors. The fluorescence intensity maintained about half of the initial intensity at 400 K, and the thermal quenching was due to the increase of non-radiative transitions at high temperature. Finally, LED devices were fabricated using 365 nm NUV chips with commercial blue, green phosphors and Ba 2 LuNbO 6 :Mn 4+ red phosphors for the use of outdoor lighting, which had color rendering index (CRI) of 84.4 and color temperature (CCT) of 5710 K. The results indicate that Ba 2 LuNbO 6 :Mn 4+ phosphors have great potential as a deep red phosphor in the field of WLEDs and plant growth light. • Deep red phosphor Ba 2 LuNbO 6 :Mn 4+ were prepared by high temperature solid state method in air atmosphere for WLEDs and plant cultivation. • The Ba 2 LuNbO 6 :Mn 4+ phosphor presents deep red emission from 650 nm to 720 nm. • Ba 2 LuNbO 6 :Mn 4+ phosphors have excellent photoelectric performance for LED application.

Structural and visible fluorescence traits of Dy3+ ion activated Lu1.5Y1.5Al5O12 phosphors

In the current work, a series of Lu1.5Y1.5Al5O12 (LuYAG) phosphors doped with different Dy3+ ion concentrations (0.5, 1, 2, 3, 4, and 5 at% in nominal) have been synthesized by high-temperature solid-phase approach and characterized by X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy, transmission electron microscopy, optical absorption, emission, and decay lifetimes. The shape and position of Dy3+ ion absorption peaks were consistent in all samples, and the absorption peak intensity increased with enhancing Dy3+ concentration. Under λexci. = 448 nm, 4F9/2 → 6H15/2, 13/2, 11/2, 9/2 emission transitions have been identified in which the 4F9/2 → 6H13/2 transition possesses the highest intensity. Luminescence decay times were evaluated for Dy3+: 4F9/2 level. Relying on the absorption and luminescence spectra, along with fluorescence decay patterns, the optimal doping concentration of 1 at% was identified. The energy transfer process between Dy–Dy ions was discussed and utilized to explain the concentration quenching phenomenon. Notably, 1 at% Dy: LuYAG could be used as a potential candidate for commercial yellow phosphors.

Design of novel cyan phosphor Ca7NaLu(PO4)6:Eu2+ for full-visible-spectrum white LED: enhanced thermal stability and tuned emission by neighbor cation effect

Cyan phosphor is desirable to fill the cyan gap (480–520 nm) in white light-emitting diodes (wLEDs) to achieve full-visible-spectrum lighting. In this paper, a novel highly efficient cyan emitting Ca7NaLu(PO4)6:Eu2+ (CNLP:Eu2+) phosphor was synthesized, exhibiting broadband and bright emission ranging from 425 to 675 nm and an excitation band ranging from 250 to 450 nm. Notably, CNLP:0.09Eu2+ shows an excellent internal quantum efficiency of 90% and a high external quantum efficiency of 57.6%. In addition, a neighbor cation effect induced by replacing Ca with Sr was used to design a series of Ca7-ySryNaLu(PO4)6:Eu2+ (C7-ySyNLP:Eu2+y = 1, 4, 7) phosphors with a good thermal stability and tunable emission. The spectra of the C7-ySyNLP:Eu2+ phosphors undergo a red shift and the full width at half maximum increase from 78 to 100 nm with an increase of Sr content. Furthermore, a near-ultraviolet pumped wLED that fills the cyan gap was fabricated by composing CNLP:0.09Eu2+ with commercial phosphors, showing high color rendering index (Ra = 95). The excellent luminescent properties of as-prepared phosphors indicate they are promising for the production of high-color rendering index full-visible-spectrum wLEDs.

Thermally stable red luminescence from Eu3+ -activated telluro zinc phosphate glass under near-ultraviolet light excitation for photonic applications.

Telluro zinc phosphate (TZP) glasses doped with different concentrations of Eu3+ ions were prepared and their physical, structural, and luminescence properties were studied in detail to reveal the utility of the as-prepared glass for white light-emitting diode (w-LED) applications. The broad hump in the diffraction pattern specified the amorphous behaviour of the TZP glass. The various vibrational shoulder linkages were characterized using the Fourier transform infrared (FT-IR) spectroscopy. The optical absorption spectrum was measured in the ultraviolet (UV)-visible (Vis) light region for the Eu3+ -doped TZP (TZPE) glass and the optical band gap was found to be 3.12 eV. Eu3+ -doped TZP glasses showed several emission peaks in the visible region including an intense red emission peak due to the 5 D0 →7 F2 transition under an excitation wavelength of λex = 393 nm, which was matched with the emitting wavelength of the near-UV LED chip. Commission Internationale de I'Eclairage (CIE)chromaticity coordinates were situated in the red region and nearly matched with the coordinates of the commercial red phosphor (Y2 O3 S:Eu3+ ). The decay profile of the TZPE50 glass exhibited a single exponential fit with a decay time ( of 1.76 ms. Temperature-dependent photoluminescence (TDPL) studies demonstratethat the as-prepared glass consist of excellent thermal stability. The detailed analysis and results confirmed that the red-emitting TZPE glasses were potential candidates for white-LED and other photonic applications.

Long Persistent Afterglow Luminescence in Gd<sub>3</sub>Al<sub>3</sub>Ga<sub>2</sub>O<sub>12</sub>:Ce<sup>3+</sup>, Green Emitting Aluminate Phosphor

Green LL is observed in Ce doped Gd3Al5O12: Ce, Ga garnet phosphors. LL is well correlated with Ce3+ emission and a peak around 150°C in the TL glow curve. In comparison with the commercial phosphor YAG, the Gd3Al5O12: Ce, Ga (GAG) is more stable and shows more intense TL properties, this phosphor can be used for dosimetry detections and measurements. Gd3Al5O12 activated with Ce (0.7 mol.%) phosphors were prepared by combustion synthesis. The long-lasting luminescence (LL) is also reported in Pr3+ and Ce3+ doped in reducing atmosphere in YAG phosphor. But YAG: Ce gives yellow emission which doesn’t suit LL applications. On the other hand, Ga substituted GdAG: Ce phosphor gives green emission at shorter wavelengths. In this paper we explored Ga substituted GdAG: Ce phosphor prepared by combustion synthesis for LL, results of these investigations are reported in this paper.

Color-tunable blue-emitting Na2MgSiO4:Ce3+ phosphors for white light-emitting diodes

Phosphor-converted white light-emitting diodes (pc-wLEDs) based on near-UV LED chip demand efficient blue-emitting phosphors, because the pc-wLED uses either multi phosphors or single-phase white-emitting phosphor both needs blue-emitting component. When using Ce3+ as the activator, the host structure usually has rare earth ions or alkaline earth ion such as Ca2+ for Ce3+ to occupy, due to similar ionic radius and charge. This work is going to report a blue-emitting phosphor Na2MgSiO4:Ce3+, where Ce3+ occupies the Na+ sites. The phosphor exhibits characteristic of tunable emission color upon increasing Ce3+ content or introducing Li+ as charge compensator. The relationship between the crystal structure and the luminescent properties was studied in detail based on structural refinement and in-depth luminescent studies. The phosphor with a proper Ce3+ content showed a high absolute quantum efficiency of 86.0% and acceptable thermal stability. The pc-wLED made of 365 nm UV chip, the as-prepared Na2MgSiO4:Ce3+,Li+, and commercial green and red phosphors showed good performance with color rendering index of 93.3.

Photoluminescence Properties of Cyan-Emitting Lu3GaxAl5-xO12: Ce3+ Garnet Phosphors Synthesized in Nonreducing Atmosphere and at Different Temperature for High Quality w-LEDs.

The existence of so-called blue-green cavities in the luminescence spectrum has been a hindrance to the improvement in the performance of traditional phosphor-converted white light emitting diodes. The commercial phosphors synthesized in reducing atmospheres can also cause problems such as equipment complexity, increased cost, and environmental pollution. Herein, a series of cyan-emitting Lu3GaxAl5−xO12: Ce3+ (x = 0, 1, 2, 3, 4) garnet phosphors were synthesized by a traditional solid-state reaction in a nonreducing atmosphere at different temperatures. The crystal structure, grain morphology, optical properties, and thermal quenching behavior were used to analyze the optical properties of the as-prepared phosphors. The luminescence intensity of samples is affected by the synthesis temperature and energy gap between the conduction band and the lowest energy of the 5d excited state of the host lattice. With the substitution of Al3+ by Ga3+, the regularity of the excitation and emission band movement is determined by the combined effects of crystal field splitting (CFS) and the nephelauxetic effect (NE). The temperature dependence of luminescence was studied. The thermal quenching mechanism was clarified by the thermal ionization model. Finally, by employing Lu2.94Ga2Al3O12: Ce3+0.06 as a cyan component, a w-LED with a high color rendering index of 93.2 and low correlation color temperature of 3880 K based on a blue chip and commercial red phosphors were fabricated in order to explore its possible application in high quality w-LED.

Novel near-ultraviolet-excited and thermally-stable blue-emitting phosphor for healthy WLED lighting

The widespread popularity of white light-emitting diodes (WLED) lighting results in a chronic exposure to blue light, which has negative impacts on human biological functions, emotions and health. As an alternative strategy, integrating near-ultraviolet (n-UV) LED chips with high-efficiency (high quantum efficiency, chemical and thermal stability) tricolor phosphors, can easily achieve high-quality white light and diminish the so-called “blue-light hazard”. However, few blue-emitting phosphors can meet the aforementioned requirements. Herein, we report a novel n-UV excited bright blue-emitting CsBaB9O15:2%Eu2+ phosphor with high internal quantum efficiency (IQE = 68.8%) and outstanding thermal stability (94.2%@ 150 °C, 84%@ 250 °C). Impressively, this phosphor exhibits excellent chromaticity stability (Δx = 0.002, Δy = 0.012; 3.6 × 10−3 ≤ ΔE ≤ 8.1 × 10−3) from 25 to 150 °C. These remarkable thermal stability are mainly ascribed to the large band gap of host (Eg = 5.85 eV), which effectively suppresses the thermal ionization pathway of the dominant 440 nm emission in the CsBaB9O15:2%Eu2+ phosphor. A WLED device was fabricated by combining commercial phosphor Sr2Si5N8:Eu2+, green phosphor (Sr, Ba)2SiO4:Eu2+ and as-synthesized blue phosphor with a 380 nm n-UV LED chip, which exhibits high color-rendering index (CRI = 90) and low correlated color temperature (CCT = 3301 K). These results demonstrate that the outstanding CsBaB9O15:Eu2+ blue phosphor could be a candidate for next-generation healthy WLED lighting.

Synthesis and emission enhancement of intrinsic green-emitting materials for versatile applications

The intrinsic green-emitting Sr2Sb2O7 phosphors with an orthorhombic structure were synthesized. Meanwhile, the doping of Bi3+ ions greatly enhanced the luminescent properties of Sr2Sb2O7 material by increasing the particle size and supplying the 3P1 → 1S0 emission. The strong green-emitting Sr2Sb2O7:Bi3+ phosphors with excellent moisture resistance and structural stability can be used for some practical applications. The packaged light-emitting diode (LED) devices based on the Sr2Sb2O7:Bi3+ phosphors with and without commercial phosphors were fabricated. Practically, the white LED device exhibited a warm white emission with the color rendering index and correlated color temperature values of 85.36 and 4185 K, respectively. Besides, the Sr2Sb2O7:Bi3+ security inks with good water resistance were presented. Finally, the prepared materials have also been successfully applied to latent fingerprint detections and flexible films. Therefore, these strong green-emitting materials are suitable for various optical applications.

Development of novel Eu2+ and Li+ Co-doped cyan-emitting aluminosilicate phosphors

The cyan emission band contains blue and green light regions, which can simplify the fabrication process of white light-emitting diodes and help promote the development of solid-state lighting. In this paper, a series of Eu2+ singly doped and Eu2+ and Li+ co-doped cyan light-emitting KAlSiO4:x Eu2+, y Li + materials were synthesized using the high temperature solid-state method. It was found that the incorporation of 10% Li + could increase the emission intensity of the KAlSiO4:0.02Eu2+ sample by up to a factor of ∼3. This also shifted the emission color of the sample from blue-cyan (472 nm) to cyan (485 nm), and the quantum yield was increased from 71.5% to 93.3%. When the temperature is increased to 150 °C, the peak emission intensity was increased from 75.9% to 92.7% of that at room temperature. DFT calculations were used to demonstrate that the KAlSiO4 phosphor host possesses a wide bandgap of 4.86 eV and the experimentally-determined optical bandgap of the phosphor was 5.6 eV. The phosphor was combined with a commercial red phosphor, and these together were used as the emitting components in a white LED package. The characteristics of the white LED when using two representative samples of the phosphor (KAlSiO4: 0.02Eu2+ and KAlSiO4: 0.02Eu2+, 0.1Li+) were examined; these white LEDs had color rendering indices of 82 and 95, and color temperatures of 5656 K and 4126 K respectively. This work demonstrates the significant potential that KAlSiO4:0.02 Eu2+, 0.1 Li+ phosphors have in the field of LED lighting.

Seeking new, ultra-narrow-band blue emitting phosphors with high color purity for wide color gamut displays

Ultra-narrow-band phosphors have gained widespread applications in lighting and displays to enhance brightness and improve color saturation. Typical phosphor designs employ UCr4C4-type compounds and designing new narrow-band phosphors with high color purity is a major challenge. Here, we explored a Eu2+-doped Ba5GeO4Br6 phosphor, showing a narrow-band blue emission (λem = 436 nm) excitation at the near-ultraviolet light with a full width at half maximum of 30.7 nm and high color purity of 96.6%. In addition, attractive cathodoluminescence characteristics were systematically analyzed by varying filament current (30–70 mA) and accelerating voltage (3–7 eV). Robust anti-degradation behavior and color point stability under continuous electron beam bombardment were confirmed. Given its excellent performance in photoluminescence and cathodoluminescence, application in wide color gamut displays appears promising. Using commercial phosphors β-SiAlON:Eu2+ and K2SiF6:Mn4+ as green and red light converters respectively, and the title phosphor as the blue light converters, the fabricated w-LED exhibits a wide color gamut of 82% NTSC.

Synthetic-Method-Dependent Antimony Bromides and Their Photoluminescent Properties.

Recently, excellent optical properties of low-dimensional organic-inorganic metal halides, stemming from their tunable structure and optoelectronic properties, have been demonstrated. The synthetic method is critical because it is highly related to the structure and properties of the halide. Herein, we obtain two different antimony bromides, (Bmpip)2SbBr5 and (Bmpip)3Sb2Br9, which both possess the P21/c space group having different crystal structures, and this confirms the important influence of synthesis on the single-crystal structure. (Bmpip)2SbBr5 contains Bmpip+ and [SbBr5]2- pyramids, and (Bmpip)3Sb2Br9 consists of Bmpip+ and Sb-based dimers [Sb2Br9]3-. Under 400 nm excitation, (Bmpip)2SbBr5 exhibits a 640 nm orange emission with a quantum yield of ∼11.5% owing to Sb 5s2 electron luminescence. A diode was fabricated by (Bmpip)2SbBr5 and commercial phosphors and showed a high color render index of 92. Our work reveals the effect of the preparation method on the crystal structure. A luminescent material was finally identified.

High quality germanate phosphor La(2-x-y)Ge2O7: Tb3+, Eu3+for WLED applications

White light emitting diodes (WLEDs), as the fourth generation of new light source, has the advantages of light weight, small size, low energy consumption, fast response speed and convenient use, but their poor thermal stability, high correlation color temperature (CCT) and low color rendering (Ra) limit their large-scale application of high-power WLED. In this work, we report the preparation of WLEDs by combining rare earth ions Tb3+-Eu3+ with La2Ge2O7, which exhibits tunable photoluminescence properties and excellent thermal stability. The detailed study shows that the layered structure of the material is conducive to efficient energy transfer (ET) between Tb3+ (sensitizer) and Eu3+ (activator), and effectively inhibits the luminescence attenuation caused by concentration quenching. Based on this, the doping ratio of Tb3+/Eu3+ in the phosphor is controlled and the phosphor is combined with blue chip to obtain excellent white light (CCT = 3955 K). The light efficiency (87 lm w−1) is comparable to that of commercial phosphors, and there is no significant decrease after continuous operation for 1000 h, which provides a good candidate material for the preparation of high-power WLED.