Red Luminescent Material Research Articles

Structural and spectroscopic characteristics of Eu3+ embedded titanium lead phosphate glasses for red luminescence

A series of Eu3+ incorporated titanium lead phosphate glasses with the chemical compositions of 1 mol% Eu2O3+ xTiO2+(50–x)PbO+49P2O5 (where x = 1, 3 and 5) have been prepared by the melt quenching procedure. Structural investigations have been performed through XRD and FTIR spectra. Optical properties are investigated by absorption, excitation, photoluminescence emission, decay lifetime and CIE chromaticity measurements. Using absorption transition from 7F0 and 7F1 levels, the nephelauxetic ratio (β) and bonding parameter (δ) are estimated to determine the type of bonding between Eu3+ ions and the surrounding ligands. The absorption as well as the excitation spectra show that the band at 393 nm corresponding to 7F0 → 5L6 transition is very strong. Upon excitation at 393 nm, Eu3+ embedded titanium lead phosphate glasses exhibit maximum emission intensity for 5D0 → 7F2 transition at 611 nm which emits red color. Using Judd-Ofelt (JO) theory, the JO parameters Ω2, Ω4 and Ω6 have been estimated from the absorption and these parameters follow the trend of Ω2>Ω4>Ω6 for all glasses. These JO parameters are used to predict the branching ratio (βR), radiative transition probability (AR), stimulated emission cross-section (σPE) and radiative lifetime (τR). The larger value of spontaneous emission cross-section, suggests that the present glass samples are encouraging materials for Eu3+ embedded optical amplifiers and laser materials. Using the decay profile which shows single exponential, the luminescence decay lifetime of Eu3+ ions for the 5D0 metastable state is evaluated. The fluorescence quantum efficiencies have been evaluated which indicate that the values may be enhanced with the increase of titanium dioxide (TiO2) in the glass matrix. The color purity (CP) of the red emission and correlated color temperature (CCT) of these samples are calculated using the CIE (Commission Internationale de l’Eclairage) chromaticity diagram. Our investigation reveals that the present glasses may be utilized as red luminescent materials and red laser source for 5D0 → 7F2 emission at 611 nm.

Luminescence properties of composite material Sr2MgSi2O7:Eu2+,Dy3+/light conversion agent with multilayer structure

In order to improve the red luminescent properties, Sr2MgSi2O7:Eu2+,Dy3+ was selected as a blue persistent luminescent donor phosphor, while light conversion agent was utilized to tune the persistent luminescent spectra from blue to red. Composite red luminescent material Sr2MgSi2O7:Eu2+,Dy3+/light conversion agent (SMED/LCA) was fabricated with light conversion agent and Sr2MgSi2O7:Eu2+,Dy3+ at a certain mass ratio. SiO2 (Al2O3 or MgF2) were coated on the surface of SMED/LCA through heterogeneous deposition method. The structural and optical characteristics of the resulting samples were launched in terms of X-ray diffraction and emission spectrum as well as afterglow brightness. The results demonstrate that the emission spectrum exhibits two emission bands, and the peaks are located at around 470 and 615 nm. SiO2, Al2O3 and MgF2 are coated on the surface of SMED/LCA like a protective shell to maintain its stability and luminescent properties, the afterglow initial brightness is still up to 0.37 cd/m2 and the afterglow color purity calculated from CIE color coordinates is basically unchanged.

Synthesis and photoluminescence properties of a novel red emitting Ba3ZnTa2O9: Eu3+ phosphor

A novel Ba3ZnTa2O9: xEu3+ (0 ≤ x ≤ 0.16) red luminescent material was composition via solid-state method. The phase purity, crystal three-dimensional structure, micromorphology, UV-Vis absorption spectra, photoluminescence performance, energy transfer mechanism among Eu3+ ions was studied in detail. The Ba3ZnTa2O9: xEu3+ phosphors effectively excited under 395 nm near ultraviolet wavelength and showed intense red emission at 594 nm, corresponds to the 5D0→7F1 transition of Eu3+. It obtained from experiments that the phosphors of Ba3ZnTa2O9: xEu3+ optimal doping concentration is x equal to 0.10. The critical distance of Eu3+ ions is 15.77Å, and the non-radiative energy transfer between Eu3+ ions is mainly affected by nearest-neighbor ions. Thermal stability of Ba3ZnTa2O9: 0.1Eu3+phosphors was determined by the emission spectrum associated with temperature. The chrominance coordinates of Ba3ZnTa2O9: 0.1Eu3+ phosphors located at (0.5367, 0.4497). Owing to Ba3ZnTa2O9: xEu3+ phosphors has high color purity, illustrating it has potential application value in commercial red phosphors.

Unraveling the Eu2+ → Mn2+ Energy Transfer Mechanism in w-LED Phosphors

Recent research on white light LED (w-LED) phosphors has focused on narrow-band green and red luminescent materials to improve the efficacy of w-LEDs and to widen the color gamut of w-LED-based dis...

Analysis of trap distribution of a red persistent luminescent materials using thermoluminescence.

Trap distribution plays a crucial role in deciding the applicability of a material. The thermoluminescence (TL) parameter that describes trap distribution is η, which has never been discussed in TL analysis so far. TL analysis of a commercially available red persistent luminescent material (CaSrS:Eu) was performed using computerized glow curve deconvolution (CGCD) in the new general order kinetics. CGCD results showed that the red persistent luminescent material in the temperature range 300-600º K was comprised of nine peaks. Activation energy ranged from 0.66-1.27 eV. Frequency factor was in the range 109 to 1011 sec-1 . The major peaks of the red persistent luminescent material had lesser empty traps. The most important information provided by the analysis was that the major peaks of the red persistent luminescent material had 30-60% of the empty traps close to the filled traps, and this accounted for retrapping of thermally released electrons. This finding suggests that the occurrence of 30-60% empty traps close to the filled traps is a necessary requisite for a persistent luminescent material.

Enhancement of luminescence properties of SrAl2Si2O8: Eu3+ red phosphor

Aluminosilicate phosphors have been widely used in the fields of fluorescence and laser technology due to its excellent optical properties. However, red phosphors have low luminescence efficiency, and poor physicochemical stability, which cannot achieve efficient white light emission. Therefore, improving the luminescence performance of aluminosilicate red phosphors is a research hotspot in white LED. In this work, SrAl2Si2O8: Eu3+ red phosphor was synthesized by high temperature solid-phase method. By introducing charge compensator and flux, the luminescence intensity of the phosphor is increased. The best charge compensator is determined as Li+ with the same Eu3+ doping content. The best flux is H3BO3, and the optimal doping concentration of flux is 3 wt%. For SrAl2Si2O8: Eu3+, Li+, H3BO3 red phosphor, the CIE coordinates are (0.619, 0.380) and CCT is 3417 K, which is very close to the standard red light. Through LED packaging mixing phosphor with YAG: Ce3+, the method can significantly improve the color rendering index of WLED, up to 84.7. When the temperature reaches 150 °C, the luminescence intensity decreases to 88.02% of the initial value, which indicates that the SrAl2Si2O8 phosphor is an excellent stable red luminescent material.

A novel promising red phosphor Ca9LiBi0.667(PO4)7:Eu3+ with excellent responsiveness to phytochrome PFR for the indoor plant cultivation

A new red luminescent material Ca9LiBi2/3(PO4)7:Eu3+ (CLBPO:Eu3+) was synthesized by high temperature solid state reaction, and characterized by X-ray powder diffraction (XRD), field emission scanning electric microscopy (FESEM) and fluorescence spectroscopy. The XRD patterns indicated that CLBPO:Eu3+ phosphor has been successfully synthesized. The photoluminescence excitation (PLE) spectra and emission (PL) spectra of phosphor, as well as the relationship between PL intensity and concentration were discussed. The results exhibit that the PL peak of CLBPO:Eu3+ phosphor is mainly centered at 616 nm under 395 nm excitation, which is attributed to 5D0→7F2 transition of Eu3+ ions. In addition, the 5D0 → 7F4 transition around 700 nm belongs to the far-red emission, which matches well with the far-red absorption wavelength required for plant photosensitive pigments PFR. Moreover, when the doping concentration of Eu3+ is 80 mol%, the PL intensity of phosphor reaches the maximum. The calculated International Commission on Illumination (CIE) coordinates lie in the red region and the color purity of CLBPO:0.8Eu3+ is determined to be 99.76%. The correlated color temperature (CCT) value of CLBPO:Eu3+ is less than 3500 K, belonging to warm red light. In view of the aforementioned interesting luminescent properties, the prepared phosphor possesses high application potential in the fabrication of phosphor-converted white light emitting diodes (WLED), and plant growth lighting.

Preparation and luminescence of rare earth complex Eu(DBM)3(TPPO)

Using Eu2O3 as source of europium, anhydrous ethanol as solvent system, methylene benzoyl(DBM) as first ligands, triphenyl phosphine (TPPO) as second ligands, the europium(III) ternary rare earth complex Eu(DBM)3TPPO has been successfully prepared. The samples were characterized by fluorescence spectrum(FS), Fourier transform infrared spectroscopy(FT-IR), thermogravimetry differential scanning calorimetry(TG-DS) and scanning electron microscope(SEM). The influence of TPPO on luminescence intensity, color temperature, color coordinates, morphology and thermal stability of the samples were analyzed. The results showed that the addition of second ligand could enhance the luminescence intensity of Eu(DBM)3TPPO. Eu(DBM)3TPPO can emit strong red fluorescence when excited by 395nm ultraviolet light. The color coordinate of Eu(DBM)3(TPPO) is (0.63, 0.36). The Eu(DBM)3TPPO is a kind of red luminescent material with wide application prospect.

Red luminescent metal–organic framework phosphor enhanced by CaSrS:Cu,Eu for agricultural film

A bright red luminescent composite material was prepared by combining a luminescent europium-based metal–organic framework (Eu-MOF) host with a red emitting sulfide (CaSrS:Cu,Eu). CaSrS:Cu,Eu particles were first prepared by calcination, and then these particles were used in a hydrothermal synthesis of Eu-MOF. By this approach, the CaSrS:Cu,Eu particles were naturally incorporated with the MOF. The luminescent properties indicated that the red emission intensity of the CaSrS:Cu,Eu@MOF product was much higher than that of the Eu-MOF itself due to the energy transfer from CaSrS:Cu,Eu to Eu-MOF. Furthermore, CaSrS:Cu,Eu@MOF displays enhanced emission intensity at the range of 400–500 nm and 600–700 nm, which are just the main absorption range for crops and plants. Thus, the prepared CaSrS:Cu,Eu@MOF was applied to prepared agricultural film. Results suggest that CaSrS:Cu,Eu@MOF could be a useful additive to polymer films for the agricultural sector.

Study on TICT emission of TPE-BODIPY derivatives mediated by methyl group on BODIPY

A series of tetraphenylethene-borondipyrromethene (TPE-BODIPY) derivatives with different numbers of methyl groups on BODIPY cores were designed and synthesized. The intramolecular charge transfer behaviors from donor TPE to accepter BODIPY were investigated. Aggregation-induced emission (AIE), theoretical calculation, single crystal structure and solvent effect all proved that the introduction of methyl group to BODIPY can inhibit the intramolecular charge transfer behavior. Red organic luminescent material 8-TPEBODIPY (TPB) with no methyl groups showing twisted intramolecular charge transfer (TICT) emission peak both in solution and in film state, presents obviously AIE and solvatochromic properties and a large Stokes shifts over 100 nm, which can be employed as a fluorescent sensor for the detection of water in THF.

Self-Propagating Combustion Synthesis, Luminescent Properties and Photocatalytic Activities of Pure Ca12Al14O33: Tb3+(Sm3+).

The dual-functional Ca12Al14O33: Tb3+ and Ca12Al14O33: Sm3+ materials were prepared by the Self-Propagating Combustion Synthesis (SPCS) technology. The structure, morphology and light absorption property were investigated by XRD, FT-IR, UV-Vis DRS and SEM etc. The doping of Tb3+ and Sm3+ ions had not changed cubic structure of Ca12Al14O33 but leaded to the slight lattice dilatation and the red-shifts of absorption peaks/edges. The excitation and emission spectra indicated that Ca12Al14O33: Tb3+ and Ca12Al14O33: Sm3+ are superior green and red luminescent materials, respectively, and it displayed the distinctly refined structure characteristics which had importantly reference value for the energy level investigation of Tb3+ and Sm3+ ions. Meanwhile, Ca12Al14O33: Tb3+ and Ca12Al14O33: Sm3+ also exhibited the improved photocatalytic degradation for removing dye MB compared with bare Ca12Al14O33.

Toward Bi3+ Red Luminescence with No Visible Reabsorption through Manageable Energy Interaction and Crystal Defect Modulation in Single Bi3+-Doped ZnWO4 Crystal

The last decades have witnessed the discovery of tens of thousands of rare earth (RE) (e.g., Eu2+) and non-RE (e.g., Mn2+) doped photonic materials for near-ultraviolet (NUV) and blue converted white light-emitting diodes (wLEDs), but the future development of wLEDs technology is limited greatly by the intrinsic problems of these traditional dopants, such as the insurmountable visible light reabsorption, the weak absorption strength in NUV or blue region, and so on. Here we report a feasible strategy guided by density functional theory (DFT) calculation to discover novel Bi3+ red luminescent materials, which can solve the above problems eventually. Once the untraditional ion of bismuth is doped into ZnWO4 crystal, multiple defects can be possibly created in different charge states such as BiZn, BiW, interstitial Bi, and even defect complexes of 2 BiZnVW among others, and they, as DFT calculated results illustrate, have the potential to produce emission spanning from visible to near-infrared. As confirmed ...

Promising red emission from functionalized multi walled carbon nanotubes embedded co-doped Bi3++Eu3+: PVA polymer nanocomposites for photonic applications

A bright novel sensitized red emission has been obtained from functionalized multiwalled carbon nanotubes (f-MWCNTs) embedded Bi3++Eu3+: PVA polymer nanocomposites under UV excitation. We have successfully synthesized Eu3+: PVA, Bi3++Eu3+: PVA and Bi3++Eu3++ functionalized MWCNTs: PVA polymer films by traditional solution casting method. The structural and ion-polymer interaction studies have been analysed from XRD and FTIR spectral profiles. Eu3+ doped at different concentrations in PVA polymer films has displayed a red emission at 619nm (5D0→7F2) under 396nm (7F0→5L6) of excitation. Upon co-doping with Bi3+ ions in different concentrations to the Eu3+: PVA polymer film, it exhibits enriched red emission than single Eu3+: PVA under the same excitation due to energy migration from Bi3+ to Eu3+. Successful emission photons of Bi3+ ions are collectively absorbed by the Eu3+ ions which lead the improvement of red emission. In the same fashion, enriched red emission is observed from f-MWCNTs impregnated co-doped Bi3++Eu3+: PVA polymer composites. The red emission of Eu3+ is significantly enhanced in two ways through an efficient energy migration process from Bi3+ to Eu3+ and f-MWCNTs to Eu3+. Possible energy transfer mechanism is clearly demonstrated by several fluorescent methods. From these results, these f-MWCNTs embedded Bi3++Eu3+: PVA polymer films might be recommended as promising candidates for red luminescent materials for photonic devices.

LnBSb2O8 (Ln = Sm, Eu, Gd, Tb): A Series of Lanthanide Boroantimonates with Unusual 3D Anionic Structures

A series of lanthanide boroantimonates, namely, LnBSb2O8 (Ln = Sm 1, Eu 2, Gd 3, and Tb 4) have been successfully synthesized by high temperature solid-state reactions for the first time. They are isostructural and feature novel three-dimensional (3D) frameworks composed of 2D [Sb3O12]9- layers interconnected by 1D [SbBO7]6- chains with remaining BO3 groups hanging on the walls of the 1D 6-membered-ring (MR) tunnels along the a-axis, and the lanthanide ions filled in the voids of the anionic structure. They exhibit high thermal stability (up to 900 °C). Luminescent studies suggest that compounds 1, 2, and 4 have potential application as orange, red, and green light luminescent materials, respectively. Magnetic measurements reveal ferromagnetic coupling interactions in compound 3 and antiferromagnetic coupling interactions between magnetic centers in compounds 1, 2, and 4.

Thin-Film Photoluminescent Properties and the Atomistic Model of Mg2TiO4 as a Non-rare Earth Matrix Material for Red-Emitting Phosphor

Thin-film electroluminescent devices are promising solid-state lighting devices. Red light-emitting phosphor is the key component to be integrated with the well-established blue light-emitting diode chips for stimulating natural sunlight. However, environmentally hazardous rare-earth (RE) dopants, e.g. Eu2+ and Ce2+, are commonly used for red-emitting phosphors. Mg2TiO4 inverse spinel has been reported as a promising matrix material for “RE-free” red light luminescent material. In this paper, Mg2TiO4 inverse spinel is investigated using both experimental and theoretical approaches. The Mg2TiO4 thin films were deposited on Si (100) substrates using either spin-coating with the sol–gel process, or radio frequency sputtering, and annealed at various temperatures ranging from 600°C to 900°C. The crystallinity, microstructures, and photoluminescent properties of the Mg2TiO4 thin films were characterized. In addition, the atomistic model of the Mg2TiO4 inverse spinel was constructed, and the electronic band structure of Mg2TiO4 was calculated based on density functional theory. Essential physical and optoelectronic properties of the Mg2TiO4 luminance material as well as its optimal thin-film processing conditions were comprehensively reported.

A Luminescent Three-Dimensional Coordination Polymer Based on Cu(I) Halide Clusters Showing Dia Topology with 8-Fold Interpenetration

One interesting copper(I) halide-based coordination polymer with a formula of [Cu4(Br)4(bib)2]n (1) (bib = 1,4-bis(imidazol-2-methyl)butane) has been prepared by solvothermal method, and characterized by X-ray single crystal diffraction, elemental analyses, IR and TGA. Structure analyses reveal that the compound is constructed of copper(I) halide clusters and flexible bib ligands, which features a 8-fold interpenetrated 3D framework with 4-connected extended dia topology. Furthermore, the compound exhibits high thermal stability and intense fluorescent emission, and can be explored for potential red luminescent materials.

Synthesis and Luminescent Properties of CaSnO3:Eu Nanopowder Prepared by a Sol-Gel Route.

Luminescent properties of nanocrystalline CaSnO3:1%Eu have been investigated in order to develop novel red phosphors. The results indicate that high-quality nanoparticles with controlled stoichiometry and microstructure were prepared by a sol-gel method using citric acid and EDTA as complexes. There are two broad excitation bands located at 240 and 270 nm existing in the excitation spectrum in addition to the characteristic excitation peaks of Eu3+. Further investigations show that the excitation band located at 240 nm can be assigned to the host absorption while the Eu-O charge transfer is responsible for the 270 nm excitation band. These results indicate that the host can efficiently transfer energy to the Eu3+ ions. The more important is that since the symmetry of Eu3+ ions is lower, the pure red emission (5D9 --> 7F2 transition located at 618 nm) is predominant over all the emission. This means CaSnO3:Eu is a potential candidate for red luminescent materials.

红色发光材料发光机理的研究进展

红色发光材料是一类通过吸收能量，将其转化为光辐射的发光材料。本文综述了红色荧光粉、红色长余辉光致磷光体、稀土电致发光材料及稀土纳米发光材料的发光机理；对红色发光材料的研究前景进行了展望。 The red luminescent materials can absorb energy and transform the energy into optical radiation. The luminescence mechanisms of red luminescent materials including red fluorescent powder, red long persistence phosphor, rare earth electroluminescent material and nano rare earth lumi-nescence material were reviewed. Finally, the future research aspects of red luminescent material were discussed in this paper.

Controllable synthesis, growth mechanism and luminescence property of a novel monodisperse microsphere with a hole for Zn8[(BO3)3O2(OH)3]:Eu3+

A novel monodisperse microsphere with a hole for Zn8[(BO3)3O2(OH)3]:Eu3+ phosphor was controllably prepared by a hydrothermal method and was characterized by XRD, EDS, FT-IR, TG-DTA, SEM, and HRTEM. The influence of hydrothermal reaction time, temperature and doping concentration on the formation of Zn8[(BO3)3O2(OH)3]:Eu3+ microstructures was investigated, and an ideal monodisperse microsphere of about 5 μm in diameter was obtained at 150 °C for 12 h with the Eu3+ doping concentration of 5%, which was self-assembled by nanoplates of about 150 nm in thickness. The crystal growth mechanism was proposed as a nucleation–dissolution–recrystallization process on the basis of time-dependent experiments. The influence of Eu3+ doping concentration and reaction time on the photoluminescence (PL) properties of Zn8[(BO3)3O2(OH)3]:Eu3+ phosphor and the corresponding Eu3+ preferential site occupancy have also been investigated. The results show that the Zn8[(BO3)3O2(OH)3]:Eu3+ microsphere with a hole product exhibits both higher intensity and the highest R/O ratio under 245 nm excitation, so it can be used as a potential red luminescent material.

Sb/Mn co-doped oxyfluoride silicate glasses for potential applications in photosynthesis

A series of Sb/Mn co-doped oxyfluoride silicate glasses were prepared via the melt-quenching method to explore red luminescent materials for potential applications in photosynthesis of green plants, and these glasses are investigated by means of luminescence decay curves, absorption, emission, and excitation spectra. We find that the as-prepared glasses are transparent in the visible region and can emit strong red light under ultraviolet, purple, and green light excitations. Furthermore, energy transfer from Sb3+ to Mn2+ ions occurs in Sb/Mn co-doped glasses. The results demonstrate that the as-prepared Sb/Mn co-doped oxyfluoride silicate glasses may serve as a potential candidate for developing glass greenhouse, which can enhance the utilization of solar energy for the photosynthesis of the green plants.