Emission Phosphor Research Articles

Enhanced photoluminescence property and broad color emission of ZnGa2O4 phosphor due to the synergistic role of Eu3+ and carbon dots

ZnGa2O4 phosphors co-composited with nanoscale carbon dots (CDs) and Eu3+ were presented for the tunable color emission. Novel single phase CDs or/and Eu3+ composited ZnGa2O4 phosphors were synthesized by microwave hydrothermal method and their optical properties were investigated. The ZnGa2O4 phosphors composited with CDs exhibited an intense broad blue light emission at 421 nm and a more enhanced photoluminescence intensity than those without CDs. The Eu3+ composited ZnGa2O4 phosphors gave an ideal red color emission. The CDs/Eu3+ co-composited ZnGa2O4 phosphors exhibited a wide emission band peak at 450 nm and narrow emission peak at 618 nm. Furthermore, the tunable color emissions of CDs/Eu3+ co-composited ZnGa2O4 phosphors from blue to the white light region, and then to red were obtained with the increasing Eu3+ concentration, which can be a promising single phased phosphor candidate in light emitting diodes. Broadly tunable emission single phased phosphor is tuned firstly through the synergistic role of the non-metal element and the rare earth metal ions.

Commendable Eu2+-Doped Oxide-Matrix-Based LiBa12(BO3)7F4 Red Broad Emission Phosphor Excited by NUV Light: Electronic and Crystal Structures, Luminescence Properties.

In this work, we synthesized a new Eu2+-doped oxide-matrix-based LiBa12(BO3)7F4 broad red emission phosphor. It can emit red light peaking at ∼644 nm under NUV excitation with the coordinate at (0.6350, 0.3586) and a sensitive color gamut for eyes. This phosphor with a special kind of tunnel crystal structure and layered distribution of Ba2+ is contributed to longer wavelength emission. By theoretical calculation and analysis using local state density energy band structure simulation of Eu2+ doped in different site, the origin of the observed emission center was distinguished. Furthermore, decay curves analysis also indicated there are three possible Ba2+ sites for Eu2+ to occupy. Temperature-dependent PL spectra appeared anomalous phenomena that the intensity increases first and then decreases, which is due to the traps energy level's contribution of electron's transition. The phosphor also has cathodoluminescence (CL) property which the spectra take on typical current saturation phenomenon. The CL curves indicated that this phosphor has a very good stability under much electron beam bombardment time. After fabricated combining with BAM, (Sr, Ba)2SiO4 and our red phosphor excited under 405-nm NUV chips, warm light LED was obtained. Its CIE coordinate is (0.3475, 0.3416) and the CCT, Ra, and luminous efficiency are 4856 K, 84.1, and 72.6 lm/W, respectively.

The effect of Y3+ and Eu3+ on properties of Zn3V2O8 phosphor

In this paper, the (Zn1-xYx)3V2O8 and (Zn1-xEux)3V2O8 phosphors were successfully prepared by high temperature solid state method. The effect of the doping amount of Y3+ and Eu3+ on the luminescent properties of phosphors was discussed. The phase, surface morphology and luminescent properties of the phosphors were characterized by X ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence (PL). The results show that the phosphor is the target product, the sample of the composite particles is bulky, the excitation spectral range of (Zn1-xYx)3V2O8 phosphors is 300-400nm, the excitation peak is at 361nm, and (Zn1-xYx)3V2O8 phosphor emission spectra in the range of 420-690nm, the emission peak in 559nm. The results show that the crystal structure of Zn3V2O8 and (Zn1-xEux)3V2O8 were the same, and the particle uniformity of (Zn1-xEux)3V2O8 was better than Zn3V2O8. The emission band Zn3V2O8 and (Zn1-xEux)3V2O8 were present at the wave length of 420-690 nm, the luminescence property of (Zn1-xEux)3V2O8 was enhance by Eu-doped.

Energy-Sensitive Ion- and Cathode-Luminescent Radiation-Beam Monitors Based on Multilayer Thin-Film Designs.

A multilayer luminescent design concept is presented to develop energy-sensitive radiation-beam monitors on the basis of colorimetric analysis. Each luminescent layer within the stack consists of rare-earth-doped transparent oxides of optical quality and a characteristic luminescent emission under excitation with electron or ion beams. For a given type of particle beam (electron, protons, α particles, etc.), its penetration depth and therefore its energy loss at a particular buried layer within the multilayer stack depend on the energy of the initial beam. The intensity of the luminescent response of each layer is proportional to the energy deposited by the radiation beam within the layer, so characteristic color emission will be achieved if different phosphors are considered in the layers of the luminescent stack. Phosphor doping, emission efficiency, layer thickness, and multilayer structure design are key parameters relevant to achieving a broad colorimetric response. Two case examples are designed and fabricated to illustrate the capabilities of these new types of detector to evaluate the kinetic energy of either electron beams of a few kilo-electron volts or α particles of a few mega-electron volts.

Tunable emission, thermal stability and energy-transfer properties of SrAl2Si2O8: Ce3+/Tb3+ phosphors for w-LEDs

Ce3+/Tb3+ ions singly and co-doped SrAl2Si2O8 phosphors were synthesized by solid-state reaction method. The crystal structure, photoluminescence excitation and emission spectra, decay lifetime, energy transfer, quantum yield and thermal stability have been investigated in detail. The SrAl2Si2O8:0.04Ce3+ and SrAl2Si2O8:0.04 Tb3+ phosphors can emit blue and green light, respectively. Under 365 nm excitation, the emission color of SrAl2Si2O8:Ce3+, Tb3+ can be adjusted from blue to green by changing the proportion of Ce3+ and Tb3+ ions based on the energy transfer. With constantly increasing of Tb3+ ions concentration, the energy transfer efficiency from Ce3+ to Tb3+ in SrAl2Si2O8 host increased gradually and reached as high as 82.91%, the quantum yield was about 67.37%. The energy transfer mechanism is proved to be dipole-quadrupole interaction. Over 100 °C, 90% initial emission intensity can be still remained. The above results indicate that SrAl2Si2O8:Ce3+, Tb3+ is a potential multicolor emission phosphor for the application in w-LEDs.

A promising orange-yellow-emitting phosphor for high power warm-light white LEDs: Pure-phase synthesis and photoluminescence properties

The high correlated colour temperature (CCT) and deficient thermal stability of widely-used YAG:Ce and InGaN white light systems prompt an urgent need for more outstanding succedaneum phosphors, among which Ce-doped La3Si6N11 (LSN:Ce) phosphor has the best performance in the yellow-orange area. However, it still has not gained popularity due to its low quantum efficiency and luminance quality, caused by many factors such as irregular particle morphology and impure chemical composition, especially the difficulty of obtaining a single phase without LaSi3N5 impurity. By doping with different alkaline-earth metal elements and adjustment of the lanthanum/silicon ratio in the raw materials, LSN:Ce and MLSN:Ce (M = Ca, Ba and Sr) phosphors with high purity were synthesised in this work. Compared to Ca and Sr, doping with Ba produced a better result, not only in the crystallisation of the LSN phase, but also in the red shift of the phosphor emission. To further improve the purity of LSN phosphors, the Si/La molar ratio was increased from 2:1 to 1:1.5, and finally resulting in a single phase when the ratio reached 1:1. The white LEDs fabricated with the LSN:Ce & BaLSN:Ce phosphors and InGaN blue light chips had lower CCTs at 3900 K and 3300 K, indicating the great potential of the phosphor for application in high power and display lighting.

Tungstate flux-grown Y 10 W 2 O 21 :Eu 3+ phosphors with enhanced particle size and luminescence properties

Abstract Eu 0.5 Y 9.5 W 2 O 21 strong red emission phosphors were synthesized via a conventional solid-state reaction method with environmentally friendly tungstate flux (M 2 WO 4 , M=Li, Na, K). The growth process of the Eu 0.5 Y 9.5 W 2 O 21 phosphors was studied using X-ray diffraction, scanning electron microscopy, and thermogravimetry/differential thermal analysis. The photoluminescence properties, including emission and excitation spectra and thermal stability, were also investigated. The experimental results indicate that the particle size and morphology of the Eu 0.5 Y 9.5 W 2 O 21 phosphors depend on the type and content of tungstate flux. The luminescence intensities of the phosphors were effectively enhanced by the tungstate flux. The results also show that the Eu 0.5 Y 9.5 W 2 O 21 phosphors are very suitable for use in near-ultraviolet light-emitting diode (LED) chips (392 nm) and blue LED chips (465 nm).

Preparation of color tuned highly emissive long-lasting phosphor with warm-toned emitting color based on coating red-emitting coumarin fluorescent dye color converter and PMMA on SrAl2O4:Eu2+, Dy3+ phosphor

A color tuned highly emissive long-lasting phosphor PMMA/RECC@SAOED with warm-toned emitting color was prepared by coating a red-emitting coumarin fluorescent dye color converter (RECC) and PMMA on the surface of green emitting SrAl2O4:Eu2+, Dy3+ (SAOED) phosphors. After being characterized by SEM, FT-IR spectra, photoluminescence (PL) spectra, CIE color coordinates and afterglow decaying curve, the results demonstrated the feasibility of the prepared RECC as the warm-toned color converter for the green-emitting SAOED. After being coated with color converter, the PL spectra of PMMA/RECC @SAOED consisted of two broad bands with two emission peaks at 520 nm and 610 nm, and the intensity of spectra in the range of (576–700) nm increased gradually with the increase of color converter content. The emitting color of the PMMA/RECC@SAOED could be easily controlled by adjusting the concentration of color converter, and it moved to yellow, orange and reddish when the concentration of color converter was added to 0.3%, 0.5% and 0.9%.

A single-composition CaSi2O2N2:RE (RE=Ce3+/Tb3+, Eu2+, Mn2+) phosphor nanofiber mat: Energy transfer, luminescence and tunable color properties

CaSi2O2N2:RE (RE = Ce3+/Tb3+, Eu2+, Mn2+) phosphor nanofiber mat has been prepared via the electrospinning process and further annealing treatment. The diameter of nanofiber precursors are generally in a range of 400–600nm, which exhibits smooth and uniform surface morphology. After removing the polymer template by high temperature treatment, the fabricated mats have been transformed into a phosphor film and maintain uniform nanofiber network microstructures. Photoluminescence (PL) properties of CaSi2O2N2 phosphor nanofiber mat have been activated by Ce3+/Tb3+, Eu2+ and Mn2+. The emission color of CaSi2O2N2:Ce3+/Tb3+, Eu2+, Mn2+ phosphor mats can be adjusted by modifying the concentration of doped Tb3+/Mn2+/Eu2+ and the resultant energy transfer process. Owing to the energy transfer of Ce3+-Tb3+, the emitting color of the phosphor mat can be changed from blue to green. Meanwhile, we still found that the switching of emitting colors from blue to red and blue to yellow can be achieved via the energy transfer of Ce3+-Mn2+ and Ce3+-Eu2+, respectively. We demonstrated a white light emission phosphor nanofiber mat by using CaSi2O2N2 system, which exhibited promising applications for near-UV WLEDs.

Variable light emission by the mixture of 1:1 ratio of LiNa3P2O7:Sm3+ and LiNa3P2O7:Tb3+ phosphor under near UV excitation

Variable light emitting single-composition phosphor is synthesised via solid state reaction (SSR) method by taking equal weights of LiNa3P2O7:0.09Sm3+ (red emission) and LiNa3P2O7:0.09Tb3+ (green emission) phosphors. Phase formation of the compound was confirmed by powder X-ray diffraction (XRD) analysis and morphology of the sample was analysed using a field-emission scanning electron microscope (FE-SEM). Optical properties of sample was studied and results show that the phosphor can be excited effectively by near-ultraviolet light-emitting diodes of wavelength 374nm and 401nm. Phosphor emits bluish-green light under excitation energy of wavelength 374nm and yellow light at 401nm excitation. The chromatic properties of the LiNa3P2O7: 0.09Sm & 0.09Tb phosphor have been found to have chromaticity coordinates of (0.185, 0.324) and CRI is 41, under the excitation of 374nm, under 401nm excitation it emits light with chromaticity coordinates (0.4663,0.5102) and CRI is 56.

Complex study on photoluminescence properties of YAG:Ce,Gd phosphors

Luminescence characteristics of gadolinium co-doped yttrium aluminium garnet doped with cerium phosphors were studied. In this work, powder X-ray diffraction (XRD) spectra, elemental composition analyses, excitation and emission spectra, conversion efficiency of emission phosphor, corresponding (CIE) chromaticity colour coordinates and pulsed photoluminescence decay kinetic curves were investigated, all the measurements were performed at room temperature. The properties of the phosphors were studied by comparing the composition of the phosphors and their luminescent properties.

Investigation of luminescence from LuAG: Mn4+ for physiological temperature sensing

Optical thermometry based on luminescent materials has garnered much attention due to its many advantages. But higher sensitivity is still expected in physiological temperature range which is of special significance in medicine and biology. For this purpose, quadrivalent manganese doped lutetium aluminum garnet, Lu3Al5O12: Mn4+, or simply LuAG: Mn4+, has been successfully synthesized by sol-gel method and its temperature dependent luminescence has been investigated in the present work. Compared to the common red emission phosphors Y3Al5O12: Mn4+ (YAG:Mn4+) with same structure, LuAG:Mn4+ has a stronger crystal field strength and a higher thermal-quenching activation energy (ΔE) of 5732 cm−1. Rapid thermal quenching of the Mn4+ luminescence occurred above room temperature around 90 °C for our LuAG:Mn4+ sample. Temperature dependent decay curves of Mn4+ emission from LuAG:Mn4+ revealed that an extraordinary high sensitivity can be achieved from luminescence lifetime measurements covering physiological temperature range with a sensitivity of 3.75% K−1 at 38 °C.

Preparation and application of carbon-nanodot@NaCl composite phosphors with strong green emission.

Luminescent carbon nanodots (CDots) have attracted much attention, but their luminescence is usually quenched in solid state. Efficient green or yellow emissive CDot-based phosphors are scarce. In this work, green emissive CDot@NaCl composite phosphors were fabricated through a convenient, low cost and eco-friendly way by embedding green emissive CDots (g-CDot) in NaCl crystals. With the protection of NaCl host, the g-CDot@NaCl composite phosphors exhibit good photostability, significant resistance to organic solvents, and improved photoluminescence quantum yields up to 25%. White light-emitting diodes with tunable color temperatures (3944-5478K) and CIE coordinates have been realized based on the g-CDot@NaCl composite phosphors.

Surface-plasmon-enhanced emissions of phosphors with Au nanoparticles embedded in ITO

Au nanoparticles were embedded in a transparent conducting layer of indium tin oxide in order to evaluate the feasibility of applying a surface-plasmon (SP)-enhanced phosphor to light-emitting diodes (LEDs). The efficiency of the phosphor was improved by energy matching between the phosphor and the SP of the Au nanoparticles. After the density of the Au nanoparticles and the thickness of the spacer layer had been optimized, the efficiency of a green phosphor was improved by 64% compared to that of an isolated green phosphor. This work provides a way to fabricate high-efficiency LEDs with high color-rendering indices and wide color gamuts in white LEDs.

The Modeling of Two Phosphors in Conversion White-Light LED

Because of the high color rendering property, the two phosphors that convert into white light in a light-emitting diode are essential in the general lighting applications. Predicting the spectrum after two phosphors mix is challenging because of the mutual interaction between the absorption of long wavelength phosphor and the emission of short wavelength phosphor. To efficiently model the target spectrum, this paper provides a systematic method for simulating the concentration and proportion of two phosphors by using empirical equations. The simulated and experimental spectra overlapped effectively. The results show that the maximum differences are about 0.0046 for CIE 1931 color coordinates (x, y), about 59 K for correlated color temperature, and about five for color rendering index, respectively. The results show that this spectral optimization is an effective approach.

Using Green Emitting Phosphor for Improving Lighting Performance of In-cup Package White LED Lamps

<p>LED technology had a huge development in recent years with major benefits: long-life, high-efficiency, excellent performance, compactness. In this work, an innovative method for improving the performance of multi-chip white LED lamps (MCW-LEDs) by adding the green Ce<sub>0.67</sub> Tb<sub>0.33</sub> MgAl<sub>11</sub> O<sub>19</sub>:Ce,Tb (CeTb) phosphor to their in-cup phosphor compounding is proposed, investigated and demonstrated. Firstly, CeTb was mixed to the in-cup phosphor package of MCW-LEDs. Then by varying CeTb concentration, lumen output and angular color uniformity (ACU) of MCW-LEDs was calculated and analyzed. The results showed that the lumen output and the ACU of 7000 K and 8500 K MCW-LEDs increased significantly in comparison with others related works. This method is a prospective ideal for future improving LED manufacture.</p>

Photoluminescence and Hydrothermal Stability Correlations via Isoreticular/Structural fcu Rare-Earth Organic Frameworks Platform

Because of the discovery of a high-symmetry rare-earth hexanuclear secondary building unit, controllable design and assembly of rare-earth organic frameworks (REOFs) have become feasible. Subsequently, series of isoreticular/structural fcu REOFs platform was herein successfully produced by solvothermal reactions and reticular chemistry. After the crystal structural information and permanent porosity were confirmed, thorough investigations toward photoluminescence and hydrothermal stability were implemented. As a result, distinct and interesting luminescence behavior is observed among the series of REOFs. 1-Dy and 2-Dy mainly display ligand-centered emission, while 1-Eu and 2-Eu are predominated by metal-centered emission. More interestingly, 1-Eu reveals excitation dependent luminescence, generating the first example of a white light emission phosphor in single phase fabricated from a sole Eu3+ ion and sole organic linker. 2-Eu however does not exhibit such features and stays mostly unchanged upon the var...

High thermal stability and quantum yields of green-emitting Sr3Gd2(Si3O9)2:Tb3+ phosphor by co-doping Ce3+

A series of Tb3+ mono-doped and Ce3+-Tb3+ co-doped Sr3Gd2(Si3O9)2 phosphors with high thermal stability and quantum yields were successfully prepared via the solid state reaction. The as-prepared Sr3Gd2(Si3O9)2:Tb3+ samples showed broad excitation spectrum from 250 to 400 nm and presented characteristic emission transitions 5D4→7FJ (J=6, 5, 4, 3) of Tb3+ under 313 nm excitation, which were located at about 488, 541, 584 and 620 nm. The emission intensities of Tb3+ rose steadily in Sr3Gd2(Si3O9)2 host with the increase of Tb3+ concentration even though Gd3+ ions were completely replaced by Tb3+ ions. The Ce3+ ion as a sensitizer could efficiently improve the performance of Tb3+ ion. First, with Ce3+ co-doping, the excitation spectrum of Tb3+ monitored at 541 nm showed a similar band that responds to the violet emission of Ce3+ monitored at 416 nm. Second, the quantum yields of Sr3Gd2(Si3O9)2:Tb3+ phosphors could be enhanced from 26.6% to 80.2% by co-doping Ce3+. Finally, the co-doping of Ce3+ was also effective to improve the thermal stability of Sr3Gd2(Si3O9)2:Tb3+. As the temperature rose to 150 °C, the emission intensity of Tb3+ remained at about 83.6% of that measured at room temperature, which was better than the commercial YAG:Ce phosphor in terms of their thermal quenching properties. These results indicated that the as-prepared Sr3Gd2(Si3O9)2:Tb3+,Ce3+ samples could be used as green emission phosphors for possible applications in near ultraviolet based WLEDs.

Synthesis, structure and multicolor-tunable luminescence of the dandelion-like SiO2:Ln3+ (Ln = Eu, Tb) nanophosphors

Dandelion-like SiO2:Ln3+ (Ln = Eu, Tb) nanophosphors of 70 nm diameter have been synthesized, and colorful emission phosphors were obtained by Ln3+ doping.

BaLu6(Si2O7)2(Si3O10):Ce3+,Tb3+: A novel blue-green emission phosphor via energy transfer for UV LEDs

A series of novel blue-green emission phosphors BaLu6(Si2O7)2(Si3O10):Ce3+,Tb3+ (BLSO:Ce3+,Tb3+) were synthesized via the high-temperature solid-state reaction route. Many characterizations such as X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR) were conducted to analyze the phase and structure of as-prepared samples. Photoluminescence (PL) properties illustrated that Ce3+ singly doped BLSO can produce a broad band ranging from 365 to 550 nm upon UV excitation, which overlapped the excitation spectrum of Tb3+ monitored at 550 nm emission. Energy transfer phenomenon from Ce3+ to Tb3+ in this kind of phosphor was demonstrated from the variations of emission spectra and the decrease of Ce3+ fluorescent decay lifetime in Ce3+-Tb3+ co-doped BLSO, based on which the emission color can be tuned from bright blue to green upon UV excitation. The energy transfer mechanism from Ce3+ to Tb3+ was determined to be electric dipole-quadrupole interaction. Moreover, the temperature-dependent PL of representative BLSO:0.18Ce3+,1.00Tb3+ was supplied in this manuscript, which indicated the good thermal stability of this kind of phosphor. The results show that BLSO:Ce3+,Tb3+ phosphors can be as a potential candidate of blue-green component in phosphor-converted UV LEDs.