Ultraviolet Chip Research Articles

Ball milling synthesis and optical properties of Na and Bi ions Co-doped double perovskite Cs2AgInCl6

Double perovskite Cs2AgInCl6 is a new direct band gap semiconductor material. Compared with traditional perovskite CsPbX3 (X = Cl, Br, I), double perovskite Cs2AgInCl6 has good stability and wide fluorescence half peak width. This study reports the mechanochemical synthesis, characterization and application of a lead-free double perovskite Cs2AgInCl6 doped with Na and Bi ions. It was found that through a facile room temperature mechanical ball milling process, the double perovskite structure can be obtained within 30 min. Then, Na and Bi ions were used to dope to optimize its luminescence properties. By this synthesis method, the sample with the best doping ratio obtained in the experiment is Cs2Ag0.7Na0.3In0.9Bi0.1Cl6 with the photoluminescence quantum yield (PLQY) of 32.7%. The X-ray diffraction (XRD) and photoluminescence (PL) results show that Na and Bi ions can promote the crystallization and optimize the luminescence properties of Cs2AgInCl6. The theoretical calculation results show that both conduction band minimum (CBM) and valance band maximum (VBM) of Cs2Ag0.7Na0.3In0.9Bi0.1Cl6 are flat, which is favorable for the generation of self-trapped excitons. Packaging Cs2Ag0.7Na0.3In0.9Bi0.1Cl6 sample on an ultraviolet (UV) LED chip, and a warm white LED with good performance can be obtained, which shows a bright potential application in the field of white LED.

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.

Rational synthesis of silane-functionalized carbon dots with high-efficiency full-color solid-state fluorescence for light emitting diodes

Highly efficient full-color solid-state fluorescent carbon dots (CDs) are very critical for the construction of light-emitting diodes (LEDs), especially white light-emitting diodes (WLEDs), but achieving them is still a challenging task due to the serious self-quenching of CDs in the aggregation state and their complicated photoluminescence (PL) mechanism. Herein, we reported a one-step microwave-assisted method for the large-scale synthesis of solid-state silane-functionalized CDs (SiCDs) with self-quenching resistant and tunable full-color fluorescence. By only controlling the ratio of precursors, the PL emission of these SiCDs can be tuned in the visible region ranging from 438 to 633 nm, accompanied by high quantum yields (QYs) of up to 26-57%. The multicolor emission of these SiCDs is ascribed to their differences in particle size and graphitic nitrogen content, which can be modulated by controlling the dehydration and condensation reactions among raw materials. In addition, based on their excellent optical properties, these SiCDs were directly utilized as phosphors combing with ultraviolet chips to prepare full-color LEDs and all types of WLEDs with adjustable correlated color temperature (CCT) from 3678 to 8158 K and high color rendering index (CRI) of 90–94, demonstrating the tremendous potential for practical lighting applications.

Novel YBO3 Phosphors Doped with Ln3+ (Ce3+, Tb3+, Eu3+) Ions with Tunable Color for WLED Applications

In this work, YBO3 phosphors doped with Ln3+ (Ce3+, Tb3+, Eu3+) ions were synthesized by a facile hydrothermal method using high temperature and high pressure environment. Structural property characterizations show all the samples have a similar spherical morphology and a hexagonal crystal structure with good crystallinity. PL spectra and CIE calculation show that the color of phosphors can be easily controlled by the species and atomic content of Ln3+ ions. White color is achieved as the atomic contents of Ln3+ ions are: 1% Ce3+, 3% Tb3+, and 0.5% Eu3+, respectively. Furthermore, LED devices based on ultraviolet chip were fabricated and characterized, and the results clearly demonstrated the tunable color of as-prepared phosphors. At the same time, co-doping Ce3+, Tb3+, and Eu3+ ions can well adjust the fluorescence lifetime of the three rare earth ions through energy transfer. These results show that the phosphor has broad application prospects in the field of display lighting such as LED.

A Triple-Doped Phosphor Strategy for the Conversion of Cool and Warm White Light.

This work proposes a new type of Eu2+, Ce3+, Mn2+ codoped strategy that can be adapted to both ultraviolet (UV) and blue chips to achieve high-quality white light illumination. Primarily, the target sample was confirmed by X-ray diffraction (XRD) and Rietveld refinement, and the surface morphology and element distribution were observed by scanning electron microscopy (SEM). Second, the energy transfer behavior and mechanism were determined by studying double-doped samples. Lu2Mg2Al2Si2O12: Eu2+,Ce3+ (LMAS: Eu2+,Ce3+) can realize an emission color adjustment from blue to yellow. The emission color of LMAS: Ce3+,Mn2+ can be adjusted from light yellow to orange yellow. Afterward, the triple-doped sample exhibits full-spectrum emission under the excitation at 365 nm, and yellow emission under the excitation at 450 nm. When combined with a 365 nm chip, the obtained light-emitting diode (LED) devices can achieve warm white light with a color rendering index (Ra) of 96.6, light emission (LE) of 1.79 lm/W, and correlated color temperature (CCT) of 4874 K. When this phosphor was combined with a 460 nm chip, cold white light with Ra = 70, LE = 13.57 lm/W, and CCT = 5782 K can be achieved. Finally, according to the properties of the phosphor, a conceptual diagram of a new type parallel device was designed, which can easily and effectively realize the conversion of cold and warm white light. This work provides a new idea for the design of single-substrate white light phosphor and proposes a new parallel device concept, which is expected to be applied in the field of lighting.

Aggregation-Induced Emission of Gold Nanoclusters by Ionic Liquids for White Light-Emitting Diode and Multiple-Ion Probe Applications.

White light-emitting diodes (WLEDs) require stable luminophores with bright emission, a large Stokes shift, and good processability. Herein, we fabricate WLEDs on the basis of synergetic aggregation-induced emission (AIE) of Au nanoclusters (NCs) induced by ionic liquids. Au NCs with orange emission at 615 nm are electrostatically bonded to 1-ethyl-3-methyl-imidazolium acetate (EmimOAc). The electrostatic bonding not only introduces complementary blue emission (from EmimOAc) into Au NCs but also enhances cluster emission via an intercluster AIE mechanism. Overall white emission of Au NC-EmimOAc composites can be further improved by their encapsulation into nanogels templated by cationic chitosan. Color conversion films constructed from these nanogels manifest ultrabright white emission on a commercial GaN ultraviolet LED chip, featuring a CIE 1931 color coordinate of (0.366, 0.368) and greatly enhanced mechanical strength. By properly selecting ionic liquids, we are also able to achieve multiple-ion detection of Cu2+, Sn2+, and Fe3+.

Synthesis and luminescence properties of Eu3+ doped sodalite phosphors using kaolin

In this paper, kaolin was used to synthesise the europium-doped sodalite phosphors (Na8(AlSiO4)6(Cl)2:Eu3+) through the hydrothermal method and then roasting processes. The influence of anion type and concentration, sodium hydroxide concentration, Eu concentration, the roasting temperature and time on the synthesized samples were investigated. Scanning electron microscopy, X-ray diffraction and photoluminescence spectroscopy were applied to detect the crystallization, morphology and luminescence intensity of obtained sodalite and phosphors. The sodalite Na8(AlSiO4)6(Cl)2 synthesized with 10 mol/L NaOH, 2.3:5 M ratios of metakaolinite:NaCl has good crystallinity and uniform particle size, when the roasting temperature and time was 850 ℃ and 2 h, the roasted samples has product has the best crystallinity and morphology. The Na8(AlSiO4)6(Cl)2:Eu3+ powder obtained with 7 % Eu concentrations had the optimal emission intensity. The photoluminescence properties results revealed that the obtained Na8(AlSiO4)6(Cl)2:Eu3+ phosphors can be excited by 396 nm near-ultraviolet light and emits red light, suggesting promising application in LED lamps matching the excitation of the ultraviolet chip.

Improving the emission intensity and broadening spectrum of borate NaSrBO3 blue phosphor by double ion doping

NaSr1-xCaxBO3:0.01Ce3+ (x = 0.2–0.7) and Na1-yKySr0.69Ca0.3BO3:0.01Ce3+ (y = 0.2–0.6) phosphors was prepared by high-temperature solid-state reaction. The crystal structure, morphology, photoluminescence and quantum yield (QY) were characterized. The emission intensity and QY of the samples were improved by double ion doping. When Ca2+ replaced Sr2+, the emission wavelength was at 416 nm, and the optimal doping concentration was 30 mol %. On this basis, introducing K and adjusting the ratio of Na and K, it turned out that Na1-yKySr0.69Ca0.3BO3:0.01Ce3+ (y = 0.2–0.6) realized spectral broadening and enhanced luminescence. This indicates that the phosphor Na0.6K0.4Sr0.69Ca0.3BO3:Ce3+ are expected to be combined with ultraviolet LED chips for white light lighting.

Zn2+-Doped Lead-Free CsMnCl3 Nanocrystals Enable Efficient Red Emission with a High Photoluminescence Quantum Yield.

The toxicity of Pb and the instability of lead halide perovskites are the main obstacles to the practical application of lead-based nanocrystals (NCs). In this paper, all-inorganic Zn2+-doped lead-free perovskite (CsMn1-xZnxCl3) NCs were synthesized by a hot-injection method. Mn2+ ions were partially replaced by Zn2+ ions, and the energy transfer between Mn2+ was effectively suppressed. Because of this, excitons are more advantageously confined to the [MnCl6]4- octahedron. Target CsMn0.95Zn0.05Cl3 NCs were endowed with red emission at 654 nm with CIE coordinates of (0.70, 0.30) closing to the standard value of NTSC, and their photoluminescence quantum yield was increased to 77.1%, which is higher than those of Mn-based lead-free perovskites previously reported. Finally, a white light-emitting diode (LED) with adjustable emission from warm to cold white was realized by mixing Cs3MnBr5, CsMn0.95Zn0.05Cl3, and a blue phosphor on a 382 nm ultraviolet LED chip.

Large Spectral Shift of Mn2+ Emission Due to the Shrinkage of the Crystalline Host Lattice of the Hexagonal CsCdCl3 Crystals and Phase Transition.

All-inorganic halide perovskite crystals are considered excellent optical host lattices for various dopants to obtain wavelength-tunable emissions with ultra-broad bands even over a wide spectral range. Here, a series of Mn2+-doped bulk ligand-free CsCdCl3 (CCC) perovskite crystals with a hexagonal shape and size of about 1 millimeter (mm) have been prepared by a facile hydrothermal method. These CCC:Mn2+ (CCC:Mn) crystals emit the representative orange-red photoluminescence (PL) of Mn2+ (4T1(G)-6A1(S)) in the centers of hexagonal octahedrons coordinated with six Cl- ions. A fine-tuning of the Mn2+ concentration from 1 to 50 mol % Cd2+ induces a substantial red shift of emission spectra from 570 to 630 nm due to the shrinkage of the crystalline host lattice, and the maximum intensity of emission is achieved at 20 mol % Mn2+ doping. A further increase in the Mn2+ concentration causes a decrease of the PL intensity due to the phase transition from CCC to CsMnCl3·2H2O (CMCH). The strong excitation bands at 360, 370, 420, and 440 nm can make the excitation of the emissive CCC:Mn crystals possible with ultraviolet (UV) and blue chips for application in white light-emitting diodes (WLEDs). The similarity of the Mn2+-concentration-dependent emission spectra excited by various wavelengths indicates that there is only one type of site for Mn2+ occupation in CCC.

Highly Efficient and Thermally Stable Ba0.75Al11O17.25: Eu2+, Mn2+ Phosphor with Dual Narrowband Blue and Green Emissions: A Promising Candidate for Wide Gamut Displays

The discovery of Eu2+‐activated narrowband green phosphor is pivotal for wide gamut liquid crystal displays (LCDs) but facing a great challenge due to the broadband emitting nature of Eu2+ ions. Alternatively, Mn2+ ions can generate extremely narrow green emission band but suffering from their weak absorption. Herein, Eu2+ ions with strong absorption are used to sensitize Mn2+ ions in the Ba0.75Al11O17.25 host. The Mn2+ ions exhibit a green emission band peaked at 515 nm with an extremely narrow bandwidth of 27 nm. More importantly, the Eu2+ ions show strong absorption at 340–380 nm and a blue emission band peaked at 450 nm with a relatively narrow bandwidth of 51 nm. Thus, the Ba0.75Al11O17.25: Eu2+, Mn2+ phosphor can be used as a dual narrowband blue and green emitting phosphor with commercial ultraviolet diode chips excitation. Moreover, this phosphor exhibits impressive overall performance that fulfills the key standards of commercial phosphors, including high emission efficiency, excellent photoluminescence thermal stability, and outstanding chemical stability. The packaged light‐emitting diode (LED) using 365 nm chips, Ba0.75Al11O17.25: Eu2+, Mn2+ and K2TiF6:Mn4+ phosphor generates a ultrawide color gamut of 121% National Television Systems Committee (NTSC) in Commission Internationale de l'Eclairage 1931 (CIE 1931).

Single Bi3+ Ultrabroadband White Luminescence in Double Perovskite via Crystal Lattice Engineering toward Light‐Emitting Diode Applications

AbstractSingle‐phase white luminescence phosphors are emerging for potential phosphor‐converted white light‐emitting diodes (pc‐WLEDs) and alternatives to trichromatic phosphor blends. In this work, Ba2ZnWO6:Bi3+ phosphors are prepared by a high‐temperature solid‐state reaction method and the luminescent properties are investigated. The broadband excitation from 250 to 400 nm is perfectly matched with the emission of nearly ultraviolet (n‐UV) InGaN chip, which ultrabroadband emission band (full width at half maximum = 217 nm) can cover a wider luminescence region. Li+/Na+/K+ codoping is more desirable for the ultrabroadband emission of Ba2ZnWO6:0.006Bi3+ due to the charge compensation and rationally designed lattice distortion while improving the thermal stability of the phosphor. Furthermore, tunable emissions can be achieved either by changing the content of doped ions or the excitation wavelength due to the different occupation of Ba2+ and Zn2+ sites by Bi3+ ions. Finally, single‐phase warm WLED ((x, y) = (0.4170, 0.4035)) devices with a correlated color temperature of 3329 K and color rendering index of Ra = 75.3 are successfully prepared using Ba2ZnWO6:0.006Bi3+, 0.03Na+ phosphor, and 365 nm InGaN chips. These results indicate that Ba2ZnWO6:Bi3+ has excellent potential as phosphor for n‐UV pc‐WLEDs and provides new ideas for the application of ultrabroadband emitting phosphors in WLEDs.

A pH-controlled synthetic route to violet, green, and orange fluorescent carbon dots for multicolor light-emitting diodes

• We develop a pH-controlled route to violet, green, and orange emissive CDs. • The sp 2 conjugated domains and content of graphite N tune the PL wavelength of CDs. • We embed CDs in starch to realize solid-state fluorescence toward multicolor LEDs. Carbon dots (CDs) with tunable photoluminescence (PL), especially with long wavelength PL, offer great potential for various applications including sensing, bioimaging, photomedicine, and optoelectronic devices. Here, we use 2,3-diaminopyridine as a single precursor to synthesize colorful CDs in different pH conditions. By simply regulating the reaction media from alkali to neutral to acid, bright CDs emitting violet, green, and orange fluorescence are prepared, respectively. Detailed characterizations reveal that the red-shift of PL is caused by the growing size of sp 2 conjugated domain and increasing content of graphite nitrogen. We embed CDs in starch to suppress self-quenching and enhance the PL quantum yields. The CD/starch composites, possessing efficient solid-state fluorescence, can be coated on the ultraviolet chips (365 nm) to fabricate multicolor light-emitting diodes toward indoor illumination. This work presents a new strategy to adjust the PL wavelength of CDs in a wide range, and clarifies the emission mechanism.

Enhanced luminescence properties of Li2MgTiO4: Mn4+, Ge4+ phosphor via single cation substitution for indoor plant cultivation

Red and far-red emitting phosphors have been widely used in phosphor-converted light emitting diode (pc-LED) devices to provide lighting for indoor plant growth, thus achieving desired product qualities. Among the many ways to optimize phosphors’ optical performance, cationic substitution is one of the most effective methods. In this study, red phosphors (Li 2 MgTi 1- x - y O 4 : x Mn 4+ , y Ge 4+ ) were synthesized by high temperature solid state method and the optical performance of phosphors were improved with increasing Ge 4+ constituents. In particular, luminescence intensity of Li 2 MgTiO 4 : 0.002Mn 4+ , 0.1Ge 4+ increased by 152% under 468 nm excitation, and the thermostability of emission intensity increases from 22% ( y = 0) to 43% ( y = 0.1), which is about twice as much. Finally, pc-LED device was fabricated via the red phosphor Li 2 MgTiO 4 : 0.002Mn 4+ ,0.1Ge 4+ coated on a 470 nm ultraviolet chip. By changing the proportion of the phosphor, the electroluminescence spectra of pc-LED device could match well with the absorption regions of plant pigments. Therefore, Li 2 MgTiO 4 : 0.002Mn 4+ , 0.1Ge 4+ phosphor has potential application in plant lighting. Furthermore, this work can offer some helpful references for improving luminescent efficiency by simply modulating the chemical composition. The luminescence intensity of Li 2 MgTiO 4 : 0.002Mn 4+ , 0.1Ge 4+ increased by 152%. The thermostability of emission intensity increases from 22% ( y = 0) to 43% ( y = 0.1), which is about twice as much. Finally, the pc-LED device could emit bright blue and red light, which matched with the absorption regions of plant pigments well.

Mn4+-activated double perovskite red phosphor for multifunctional applications

Recently, Mn4+ activated red double perovskite red phosphors have gained great attention due to their particular luminescent properties. In this study, a novel far-red phosphor Ba2LaTaO6: Mn4+ was successfully prepared by solid-state reaction. The crystal structure and bandgap structure were analyzed using X-Ray Diffraction (XRD) Rietveld refinement and density functional theory (DFT) calculations. The photoluminescent performance of Ba2LaTaO6: Mn4+ was investigated to evaluate its availability in plant growth LED and temperature sensing. The results indicate that Ba2LaTaO6: Mn4+ can match ultraviolet chips and emit a narrow-band far-red light centering at 690 nm. The emission band of the fabricated LED matches well with the absorption bands of chlorophyll-a and b. In addition, Ba2LaTaO6: Mn4+ has a high temperature sensitive (3.2% K−1 @ 450 K), which is of great value in thermal sensing. The luminescent mechanism was dissected in-depth based on configurational-coordinate model, crystal-field and Racah parameters. It is expected that the research of Ba2LaTaO6: Mn4+ offers insight into developing new functional materials.

Naphthyl-modified graphitic carbon nitride: Preparation and application in light-emitting diodes

A series of naphthyl-modified graphitic carbon nitride were prepared by using melamine, cyanuric acid as precursors and 6-(naphthalen-2-yl)-1,3,5-triazine-2,4-diamine as a molecular dopant. When their mass ratio was 20:20:1, the product (g–C3N4–Naphth20:20:1) showed the best photoluminescence performances. The emission spectrum of g–C3N4–Naphth20:20:1 was mainly at 410–650 nm and much wider than that of bulk g-C3N4 (mainly at 410–550 nm), relative to bulk g-C3N4, the maximum emission wavelength (λem,max) changed from 455 nm to 485 nm, the light color correspondingly changed from deep blue to blue-green, the PL efficiency increased from 5.1% to 11.3%. Excited by ultraviolet chips (λem,max = 365 nm), a series of LEDs using g–C3N4–Naphth20:20:1 blended in epoxy resin at 4.0 wt% together with red-emitting SrAlSiN3:Eu2+ at x wt-% (x = 0.08, 0.12, 0.16, and 0.20) as phosphors were fabricated. When x = 0.08, 0.12, 0.16, the LEDs emitted neutral white light, their correlate color temperatures (CCT) were 5277 K, 4602 K and 3794 K, color rendering indexes (CRI) were 85.4, 88.1 and 79.7, respectively. When x = 0.20, it was a warm white LED, its CCT was 3312 K and CRI was 83.3. The results suggested the naphthyl-modified g-C3N4 can be used as efficient metal-free phosphors for LEDs.

Tunable full-color solid-state fluorescent carbon dots for light emitting diodes

Carbon dots (CDs) as a class of new fluorescent materials have attracted numerous attention. However, the solid-state photoluminescence quenching of CDs is still a big challenge. In this work, self-quenching-resistant solid-state fluorescent CDs are achieved, which exhibit tunable full-color solid-state emission without any other additional solid matrices. These CDs were prepared via one-step microwave method using phloroglucinol and urea as sources by regulating reactant ratio and microwave power. The maximum emission of CDs gradually shifts from 445 to 643 nm, and solid-state quantum yield of five typical CDs with blue (B), green (G), yellow (Y), orange (O) and red (R) emission reaches up 48.2%, 26.0%, 18.5%, 13.7% and 5.7%, respectively. Moreover, multicolor solid-solid fluorescence mechanism of CDs is investigated. The G-, Y-, O-, R-CDs show aggregation-induced red-shift behavior, while B-CDs exhibit unique crystallization-induced emission enhancement property. Finally, CDs are utilized as phosphors combing with ultraviolet chip to fabricate multicolor and white light emitting diodes (LEDs). The obtained white LEDs exhibit an adjustable correlated color temperature (3937–8588 K) and high color rendering index (80–88). This study provides a novel guidance for developing self-quenching resistant CDs with multicolor emission.

White-light emission lead-free perovskite phosphor Cs2ZrCl6:Sb3+

Obtaining phosphors with white-light emission is a promising and economical approach for phosphor-conversion light emitting diodes (pc-LEDs), but traditional single-phase white light emission phosphors are inefficient. Here a white-light-emission phosphor was prepared via a co-precipitation method by doping Sb 3+ into lead-free and vacancy-ordered double perovskite Cs 2 ZrCl 6 . X-ray diffraction, X-ray photoelectron spectroscopy, and formation energy calculations confirmed that Sb 3+ ions replaced the Zr 4+ sites in the [ZrCl 6 ] 2− octahedron. The optical properties of Cs 2 ZrCl 6 :Sb 3+ were investigated and compared with those of blank Cs 2 ZrCl 6 . The origination of the emission bands was determined according to their fluorescence spectra and decay-time at an approximate temperature of 4 K Sb 3+ -doped Cs 2 ZrCl 6 exhibited white-light emission with double emission bands at 495 and 622 nm due to the 1 P 1 → 1 S 0 and 3 P 2, 1, 0 → 1 S 0 transitions of Sb 3+ , respectively. The intensity ratios of cyan light (495 nm) and the red light emission bands (622 nm) were tunable by adjusting the Sb 3+ concentration. The red component increased with increasing Sb 3+ concentration in the present experimental range. Moreover, 10% Sb 3+ -doped Cs 2 ZrCl 6 showed the strongest emission with a photoluminescence quantum yield of approximately 78% under excitation of 333-nm light White LED devices with different correlated color temperatures were achieved by combining 1% or 10% Sb 3+ -doped Cs 2 ZrCl 6 with a 310-nm ultraviolet chip, suggesting that the synthesized samples have potential applications in white-illumination LEDs. Single-phased white emitting phosphor Cs 2 ZrCl 6 : Sb 3+ and corresponding LEDs.

Luminescence properties of Eu2+ and Sm3+ co-doped in KBaPO4

Abstract KBaPO4:Eu2+/Sm3+ phosphor was synthesized via the high-temperature solid-phase reaction method. The structural properties, surface morphology, and optical properties of the synthesized samples were obtained by the X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), and fluorescence measurements. The XRD patterns indicate that the crystal structure of KBaPO4 has not been changed by co-doped with two rare-earth ions. Under the excitation of 400 nm, the Eu2+ and Sm3+ co-doped KBaPO4 phosphors showed typical emission peaks at 430 (blue), 562 (yellow), and 600 nm (red). Meanwhile, with the increase of the Sm3+ content, the photoluminescent (PL) emission intensity of Sm3+ increased until the content reaches 0.12. However, the PL intensity of Eu2+ ions gradually decreased, which indicated that there was a possible energy transfer between the two ions. Therefore, the obtained results indicated that Eu2+/Sm3+ co-doped KBaPO4 is a promising phosphor for the use in white light-emitting diodes with near ultraviolet chips.

Two strategies to achieve color adjustment of Eu2+-doped garnet Lu2Mg2Al2Si2O12 phosphors

Phosphors with excellent color adjustable properties have always been the research focus of scientific researchers. This work uses two strategies to control the luminescence behavior of Eu2+ ions in the Lu2Mg2Al2Si2O12 (LMAS) matrix. Firstly, by adjusting the Eu2+ ion concentration, the emission spectra of Lu2Mg2Al2Si2O12:Eu2+ (LMAS:Eu2+) could achieve a 39 nm red shift from 451 to 490 nm, which provides a good blue to cyan emission. Secondly, the Lu2Mg2Al2Si2O12:Eu2+,Mn2+ (LMAS:Eu2+,Mn2+) realized the tuning from the cyan to the white region by introducing Mn2+ ions, which is owing to the sensitization process of Eu2+ to Mn2+ enhancing the red-light emission. The energy transfer process was explored in detail, and the energy transfer efficiency was calculated to be more than 60%. Meanwhile, the thermal stability of the material was also studied. The thermal stability illustrates its potential application in white light-emitting diode (WLED). Under 30 mA drive current, the device obtained by using 365 nm ultraviolet (UV) chip with LMAS:0.01Eu2+,0.35Mn2+ phosphor has a color rendering index (Ra) as high as 93.1, R9 = 85, LE = 1.81 lm/W, the color coordinate is (0.3076, 0.3119) and the correlated color temperature (CCT) is 6984 K, which is obviously in the white light area. The above results indicate that LMAS:Eu2+,Mn2+ phosphors with full-visible-spectrum have potential applications in solid-state lighting.