Red Phosphor Research Articles

Spectroscopic properties of Pr3+-doped Titania-Silicate glass ceramic for photonic applications

Silicate-Titania (SiTi) glass-ceramics doped with Pr3+ (0.6, 1.6, 2.4 and 3.6 mol%) ions were prepared by sol-gel technique. The materials were characterized by powder XRD, FTIR, TEM, EDX, Optical absorption and Photoluminescence spectroscopy. The identification of non-bridging oxygen (NBO) formation and the removal of OH groups are validated through analysis of the FTIR spectra. Additionally, measurements using XRD and TEM showed that the samples contain nano-sized crystallites. The three phenomenological Judd–Ofelt (J–O) intensity parameters Ω2, Ω4, and Ω6 were obtained and used to analyze different radiative characteristics for the fluorescence levels of Pr3+ in the glass ceramic, including radiative lifetime, branching ratio, radiative transition probability and stimulated emission cross-section. Several emissions were observed in the visible region, among which the 1D2→3H4 in the orange-red region is the most intense. All of these reported branching ratios, stimulated emission cross-sections, and visible emission spectra point to the possibility of employing them as red region lasers. The CIE chromaticity coordinates from all of the emission spectra were also assessed to determine if these materials are suitable for orange-red phosphors. According to CIE chromaticity investigations, 1.6 mol% of Pr3+ ion concentration is ideal for SiTiPr glass-ceramic for use as red phosphors and possibly red lasers.

A Lu3Sc2Ga3O12: Eu3+ red-emitting phosphor with excellent optical properties and thermal stability was obtained by partially replacing Lu3+ with Gd3+ / Y3+

A novel red phosphor Lu3(1-x)Sc2Ga3O12: xEu3+(0 ≤ x ≤ 0.3) was successfully prepared by high temperature solid state method. The Lu2.4Sc2Ga3O12: 0.2Eu3+ phosphor shows strong high internal quantum efficiency and thermal stability with values of 64.79 % and 87.0 %, respectively. Based on Lu2.4Sc2Ga3O12: 0.2Eu3+ phosphor, the partial replacement of Lu3+ ions in the host by Gd3+ / Y3+ ions changes the local crystal field environment of Eu3+ ions, resulting in wonderful changes in the luminous center, and the luminous intensity at 593 nm is increased by 3.66 and 3.54 times, respectively. The decay time of Eu3+ ions is analyzed from the perspective of dynamics, and the reasons for the enhancement of luminescence after partial replacement of Lu3+ ions are discussed in detail from two aspects of phosphor structure and crystal field effect around Eu3+ ions. In addition, with the substitution of Gd3+ / Y3+ ions, the thermal stability of the sample is 90.3 %/89.4 % with excellent low thermal quenching. The thermal quenching mechanism is described by combining Debye temperature and activation energy. The sample also has a high internal quantum efficiency IQE=79.03 % / 78.24 %. Finally, under the excitation of 365 nm chip, the phosphors of Lu2.34Sc2Ga3O12: 0.2Eu3+, 0.02Gd3+ and Lu2.34Sc2Ga3O12: 0.2Eu3+, 0.02Y3+ synthesized R-LED device has extremely high color rendering index, Ra is 78.23/77.15 and color temperature is 1640.38 K/1642.97 K. The experimental results show that the Lu2.34Sc2Ga3O12: 0.2Eu3+, 0.02Gd3+ / Y3+ phosphors prepared has a wide application prospect in w-LED devices.

Effective red emission of Sb3+ sensitized Ho3+ doped Cs2NaGdCl6 perovskite under blue excitation

Red LEDs excited by blue light have a wide range of applications in plant growth due to their simple structure. The preparation of efficient red phosphors has attracted much attention from researchers. In this paper, Cs2NaGdCl6:Ho3+ Sb3+ phosphors were synthesized by the solvothermal method, which produced the characteristic emission of Ho3+5F5→5I8 at 655 nm under 460 nm excitation. The red light at 655 nm is further enhanced after the introduction of Sb3+, and the quantum efficiency can reach 39.85 %. The luminescence mechanism and energy transfer of Sb3+ and Ho3+ were further investigated. The produced phosphor was encapsulated with a 460 nm blue chip into an LED to realize red and blue dual emission, which meets the demand for blue and red light for plant growth.

Enhancing the cyan light emission of Ba9Lu2Si6O24:Ce phosphors by crystal-site engineering for full spectrum lighting

Filling the cyan gap is the key element in achieving full-spectrum illumination using violet chip to excite red, green and blue phosphors. However, designing cyan phosphors suitable for violet light excitation with excellent performance remains challenging. Herein, a novel cyan phosphor Ba9Lu2-x-nSi6O24:xCe (n-BLS:Ce) with multiple crystal sites of Ba2+ and Lu3+ for Ce3+ ions was designed and prepared via crystal-site engineering. The Ce3+ ions at Ba2+ sites emit ultraviolet light at 385 nm under 325 nm ultraviolet light excitation, and the Ce3+ ions at Lu3+ sites emit cyan light at 485 nm under 395 nm violet light excitation. The favorable occupation of Ce3+ ions at Lu3+ sites could be realized by introducing Lu vacancies. Significantly, the cyan light emission intensity of Ba9Lu1.4Si6O24:0.3Ce (n0.3-BLS:Ce) with Lu vacancies is effectively improved by 47 % compared to Ba9Lu1.7Si6O24:0.3Ce (n0-BLS:Ce) without Lu vacancies. And the emission intensity at 150 °C retains 96 % of that at room temperature. The color rendering index increases from 87.9 to 94.5 after supplementing Ba9Lu2-x-nSi6O24:xCe cyan phosphor in w-LEDs devices combining commercial red, green, and blue phosphors with a violet chip, indicating its potential practical application in full-spectrum lighting. This work also provides new ideas for the design and development of new and efficient high-quality light-emitting materials.

In-situ passivation and anchoring of perovskite quantum dots on KSF:Mn phosphor for liquid crystal display

Perovskite quantum dots (PQDs) hold immense potential for application in backlight liquid crystal display (LCD) owing to their narrow emission spectra, tunable luminous wavelength along with high photoluminescence quantum yield. However, their poor stability severely impedes the practical application of PQDs in optoelectronic devices. Here, we prepare KSF@PQDs composites by in-situ generation of green-emitting MAPbBr3 PQDs on the surface of treated KSF:Mn red phosphors. The surface treatments on KSF:Mn are employed for realization of in-situ passivation and anchoring of MAPbBr3 through chemical interaction between the NH2 group on KSF:Mn and Pb2+ on PQDs, which enables high luminescence intensity, narrow spectral width and simultaneously high photostability of PQDs. Moreover, the ratio of green-to-red emission intensity in KSF@PQDs can be easily modulated by changing APTES content during the surface treatment of KSF:Mn. Further, white light-emitting diode devices consisting of InGaN chip and KSF@PQDs composite achieve luminous efficiency of 41.6 lm·W−1, as well as wide color gamut of 116.6 % for National Television Systems Council standard and 87.2 % for Rec.2020 standard, which paves the way for the application of high stability PQDs in wide color gamut LCD.

First Principles Study of Europium doped Gallium Nitride in Wurzite Structure

In the present work, we have successfully deposited Sb antimony doped tin dioxide (SnO2) thin films with Several advantages over well known LCD's including increased brightness and viewing angle. We are currently investigating Eu doped GaN as a potential red phosphor for TEFL display applications. Eu doped GaN films were grown by solid source molecular beam epitaxy on Si (111) substates. The material was optically characterized through temperature dependent emission spectroscopy using a He-Cd laser at 325 nm for above band gap excitation. A strong red emission was obtained at 622 nm, which corresponds to an Eu3+ inner 4f-shell transition from the 5D 0 to 7F2 state. Therefore, the observed thermal quenching of red Eu emission is assigned to a strongly temperature dependent pumping process.

Strategically Developed Strong Red‐Emitting Oxyfluoride Nanophosphors for Next‐Generation Lighting Applications

AbstractRed‐emitting nanophosphors have a multirole in improvising the next‐generation bulk/micro/nano‐level lighting devices, particularly in refining white light quality and device performance. Nonetheless, it is difficult to synthesize nanosized phosphors with good yield and paralleled high absorption efficiency both in UV and blue regions, which is critical for modern lighting. Herein, new Mg14Ge4.99+σO24‐x+δFx: Mn4+ red nanoparticles with sizes below 100 nm are designed to improve not only the luminescence but also the blue light absorption. This approach has validated the applicability of red‐emitting nanophosphors into flexible UV and blue nitride nanowire light‐emitting‐diodes (LEDs), and commercial bulk LEDs, for the first time, with boosted intensity and color superiority for a variety of lighting utilizations. For these phosphor LEDs (pc‐LEDs), optimized red nanophosphor with an external quantum efficiency of ≈44.5%, color purity of ≈100%, and thermal stability of ≈72% at 150 °C is used. The optimized nanophosphor is combined with a flexible UV‐AlGaN/GaN nanowire LED and a blue‐InGaN/GaN‐LED. The resultant devices show promising red electroluminescence without any degradation at elevated currents. Finally, several unfamiliar LED packaging is designed with yellow and red phosphors implemented on 2 sets of double LED units to reach CRI > 85. The re‐premeditated LED packages are useful for high‐definition lighting.

Enhanced red emission of MgAl2O4: Cr3+/Mn4+ phosphor co-doped with alkali metal ions

A series of MgAl2O4: Cr, Mn, M (M = Li, Na, K) red phosphors were prepared by solution combustion combined with subsequently annealing treatment. The influence of Cr3+ or Mn4+ single-doping, Cr3+ and Mn4+ double-doping and alkali metal ions co-doping on the luminescence performance of MgAl2O4 phosphors were systematically investigated. XRD and SEM were used to characterize the composition and morphology of the phosphors, and the optical absorption, photoluminescent excitation, photoluminescent emission, fluorescence lifetime and chromaticity coordinate were performed to characterize their luminescence properties. Compared with Cr3+ or Mn4+ single-doped MgAl2O4 phosphors, Cr3+ and Mn4+ double-doped ones can achieve red light emission under a wide range of excitation from ultraviolet to visible light. Co doping with alkali metal ion Li enhances the fluorescence intensity and lifetime of MgAl2O4: Cr, Mn phosphors.

Phosphor Ceramic Composite for Tunable Warm White Light.

Composite phosphor ceramics for warm white LED lighting were fabricated with K2SiF6:Mn4+ (KSF) as both a narrowband red phosphor and a translucent matrix in which yellow-emitting Y3Al5O12:Ce3+ (YAG) particles were dispersed. The emission spectra of these composites under blue LED excitation were studied as a function of YAG loading and thickness. Warm white light with a color temperature of 2716 K, a high CRI of 92.6, and an R9 of 77.6 was achieved. A modest improvement in the thermal conductivity of the KSF ceramic of up to 9% was observed with the addition of YAG particles. In addition, a simple model was developed for predicting the emission spectra based on several parameters of the composite ceramics and validated with the experimental results. The emission spectrum can be tuned by varying the dopant concentrations, thickness, YAG loading, and YAG particle size. This work demonstrates the utility of KSF/YAG composite phosphor ceramics as a means of producing warm white light, which are potentially suitable for higher-drive applications due to their increased thermal conductivity and reduced droop compared with silicone-dispersed phosphor powders.

Eu3+ doped Ca3LiSbO6 and Eu3+, Li+ co-doped Ca3LiSbO6 phosphors for white light-emitting diodes

Novel antimonate Ca3LiSbO6: xEu3+ red phosphor was synthesised using a high-temperature solid-phase reaction. The effect of Eu3+ doping concentration on its crystal structure and luminescence performance was investigated. It was found that Eu3+ was at the inversion symmetry site in the lattice of Ca3LiSbO6. To improve the luminescence performance of Ca3LiSbO6: 0.05Eu3+ red phosphor, Ca3LiSbO6: 0.05Eu3+, xLi + red phosphor was synthesised. The doping of Li + can correct the charge difference generated by the substitution of Ca2+ by Eu3+, reduce the generation of defects, enhance the local symmetry of the luminescence centre of Eu3+, improve the structural rigidity, and thus enhance the luminous intensity of the phosphor. At 423 K, the luminous intensity of this phosphor was 68 % of the initial temperature, which was higher than that of the phosphor without the charge compensator Li+ (60 %), indicating that Li+ improved the thermal stability of the phosphor.

Nb-based AxNbOFy:Mn4+ (A=Na, Cs; x=2, 3; y=5, 6) red phosphors with excellent water resistance and enhanced luminescence by W6+/Mo6+ charge compensation

Mn4+ activated fluoride red phosphors are used in warm white light emitting diodes (WLEDs). However, their inherently low moisture resistance is a major barrier to their use in high humidity conditions. In this work, the Nb-based oxyfluoride phosphors AxNbOFy:Mn4+ (A = Na, Cs; x = 2, 3; y = 5, 6) were synthesized by the co-precipitation method. The crystal structure, morphology, and luminescence properties are investigated with composition variation. The non-equivalent replacement of Nd5+ ions by Mn4+ results in bright red emission under blue light excitation. These phosphors showed very good moisture resistant luminescence. The best performance was achieved by the Na3NbOF6:0.1%Mn4+, which retained 98 % of the initial fluorescence intensity after immersion in water for 60 min. In addition, the W6+ and Mo6+ are used to compensate for the charge difference between Mn4+ and Nd5+ in Na3NbOF6:Mn4+. The compensated phosphors have shown large enhancements of 169 % (W6+) and 168 % (Mo6+) in luminescence intensity. This strategy of non-equivalent doping approach of Mn4+ into the Nb-based oxyfluoride materials and the charge compensation by W6+/Mo6+ to enhance the luminescence intensity provides a new way to realize high performance red phosphors for WLEDs.

Synthesis and luminescence properties of Eu3+-activated Mg3(PO4)2 phosphors and substitution of phosphate with molybdate, tungstate and sulphate

In the present work, trivalent europium (Eu3+) ion activated Mg3(PO4)2 red phosphors have been synthesized through solid-state reaction method. X-ray diffraction (XRD) confirmed the successful formation of Mg3(PO4)2:Eu3+ phosphors with monoclinic phase with space group P21/c (14). The photoluminescence (PL) spectroscopy was used to record the excitation and emission spectrum of Eu3+ activated Mg3(PO4)2 phosphor. Under the excitation of 395 nm, the resultant samples exhibited the characteristic emissions of Eu3+ ions corresponding to the 5D0 → 7FJ transitions. The optimal doping concentration of Eu3+ ions was determined to be 0.5 mol%. The Commission Internationale de l'Eclairage (CIE) coordinates of Eu3+ activated Mg3(PO4)2 phosphor is calculated, which shows strong red emission. In addition, phosphate group replaced with molybdate, tungstate and sulfate group and found enhancement in emission intensity of prepared phosphors. The obtained results demonstrated that the Eu3+-activated Mg3(PO4)2 phosphors are very appropriate red-emitting phosphors for applications in near-ultraviolet-excited white Light emitting diodes (LEDs).

Comprehensive investigation of Y2Si2O7:Eu3+ nanophosphors for w-LEDs: Structural, Judd-Ofelt calculation and photoluminescent characteristic with high color purity and thermal stability

In recent decades, numerous red phosphors have been designed and developed. Nevertheless, many of them are unsatisfactory due to their low brightness and poor thermal stability. Look at these shortcomings; present study reports on Eu3+ doped Y2Si2O7 (YPS) phosphors, synthesized through low temperature based urea assisted gel-combustion method. Comprehensive investigations were conducted on phase purity, luminous characteristics, energy transfer mechanism, quantum efficacy, morphology, elemental makeup, band gap and thermal stability. XRD analysis was employed to verify the preparation of Y2Si2O7 matrix with triclinic structure (P-1 space group). Morphology and elemental investigations of the fabricated materials was evaluated via TEM and EDX techniques respectively. Under the illumination at 393 nm, the most strong emission band is shown in PL spectra at 613 nm (electric dipole 5D0→7F2 transition). Additionally, the dipole-quadrupole (d-q) interaction was found to be the predominant route of energy transfer among nearby Eu3+ ions and it was concluded that 3 mol % was the optimal doping concentration of Eu3+ ions. The Judd-Ofelt (J-O) theory was used for current phosphors in order to establish their Ω2 and Ω4 with other radiative parameters. The assessment of thermal stability yielded highly promising results with activation energy of 0.241 eV. Present research indicates that Y2Si2O7:Eu3+ is a promising candidate of red emitting phosphor for white light-emitting diodes.

Unlocking the potential of CsPbI3 perovskite as stable red phosphors by zeolite skeleton

Unlocking the potential of CsPbI3 perovskite as stable red phosphors by zeolite skeleton

Achieving zero-thermal quenching of Al2(WO4)3:Eu,Tb red phosphors with low thermal expansion for LEDs

Minimizing the emission loss with rising temperature is important to fundamental research and technological applications of phosphor-converted white light-emitting diodes (pc-WLEDs). Red phosphor materials are crucial for improving the illumination and backlit display quality of pc-WLEDs. In this work, non-hygroscopic Al2(WO4)3:0.05Eu3+,0.05 Tb3+ (AWO:0.05Eu,0.05 Tb) red phosphors with low positive thermal expansion are successfully developed to simultaneously achieve zero thermal quenching (ZTQ) and a highly efficient red emitting. Under the optimal 397 nm NUV light excitation, AWO:0.05Eu,0.05 Tb exhibited a strong red emission at 618 nm with a high color purity (CP) of 99.71 % and a high internal quantum efficiency (IQE) of 80.24 %. Furthermore, a warm pc-WLED device with suitable color coordinates (0.347, 0.317), high color rendering index (CRI = 90.2) and low color correlated temperature (CCT = 4737 K) was fabricated based on the as-prepared red phosphor AWO:0.05Eu,0.05 Tb. The findings suggest that the proposed phosphor holds significant promise as a red component for high-power warm pc-WLEDs, which may open up new ways for the exploration of high-performance lanthanide-activated red phosphors towards versatile applications.

A Spectroscopic Correlative Analysis of Eu3+‐Substituted Zn1‐xSnO3 Nano Phosphors for Anticounterfeiting Applications

AbstractA series of orange–red phosphors Zn1‐xSnO3:xEu3+ synthesized using a sol–gel combustion process is used to study the modified local crystal structure by site‐selective substitution of Eu3+ ions. XRD with the Rietveld refinement analysis reveals an orthorhombic ZnSnO3 structure with a space group 61. SEM and TEM with EDAX analyses confirm the flower‐like morphology of Zn1‐xSnO3:xEu3+ nanorods. Photoluminescence (PL) spectroscopy gives substantial confirmation for the inclusion of Eu3+ ions into the ZnSnO3 host. Judd‐Ofelt analysis confirms the substitution of Eu3+ ion in an asymmetric environment in ZnSnO3, which is responsible for orange–red emission at 615 nm. UV–vis–DRS analysis shows that the addition of Eu3+ ions (1% to 17% in phases of 4%) results in the formation of confined energy states with an increased band gap from 2.78 to 3.29 eV. The ability of ZnSnO3 to host Eu3+ ions signifies that it can be used as an effective luminescent material. Cyclic voltammetry analysis reveals the enhanced charge separation in Zn1‐xSnO3:xEu3+(13%) nanophosphor. The optimized Zn1‐xSnO3:xEu3+(13%) nano phosphor mixed with silicone investigated for the generation of anti‐counterfeiting patterns indicates its potential to generate high‐resolution image patterns on various surfaces under monochromatic UV or visible‐LASER LED illumination.

Europium‐Activated Perovskite Cubical SrZrO3 Red Phosphor: Synthesis, Characterization, and Sustainable Applications in PC‐LEDs and Environmental Forensic Analysis

AbstractA series of SrZrO3 : Eu3+ nano phosphors synthesized by a modified high‐temperature solid‐state reaction method. The structural, functional vibration groups, optical, morphological, luminescence and quantum yield studies were characterized through XRD, FTIR, UV, ‘SEM & HR‐TEM’ and PL analyses respectively. The SrZrO3 : Eu3+ phosphor has a perovskite orthorhombic structure and emits intense red emission around 612 nm when it is excited under 465 nm and covers NUV light range. The calculated average lifetime indicates the nature of the allowed emission transition in Eu3+ (2.44 μs). The calculated colour purity and Commission International del’ Eclairagethe (CIE) chromaticity coordinates are 97.9 % and (0.5894, 0.4031) respectively. The observed quantum yield and thermal stability for the SrZrO3 : Eu3+ (9 mol %) phosphor are 22 % and 87 % at 423 K, respectively. These obtained results suggest that SrZrO3 : Eu3+ (9 mol %) phosphor would meliorate for red‐emitting phosphor in profound RGB‐based pc‐WLED applications.

Insights into the preparation and photoluminescence properties of MgTi2O5: Eu3+ red phosphor with high color purity for w-LED applications

As one of the critical components for achieving high-quality white light emitting diodes (w-LEDs) are efficient phosphors, a series of intense red emitting Eu3+doped magnesium dititanate (Mg(1-x)Ti2O5: xEu3+; x = 0, 0.005, 0.008, 0.01, 0.02 and 0.03 mol) phosphors were prepared via solid-state reaction method. The X-ray diffraction (XRD) patterns confirmed the phase purity and orthorhombic structure of the prepared phosphors. The Ti-O functional groups were detected from the Fourier transform infrared (FTIR) spectra and Field emission scanning electron microscopy (FESEM) images revealed agglomerated spherical-like shaped phosphor particles. Under 465 nm excitation, intense red emission corresponding to 5D0→7FJ (J = 0, 1, 2, 3, and 4) transitions of Eu3+ ions were recorded in the photoluminescence (PL) spectra with an intense peak at 615 nm. The optimum concentration of Eu3+ ions was determined to be 1 mol% and the concentration quenching mechanism was due to the interaction between adjacent Eu3+ ions. The lifetime values of the samples were in the millisecond range and the internal quantum efficiency was determined to be 31.65 %. The Commission Internationale de l'Eclairage (CIE) coordinates of the optimum sample Mg0.99Ti2O5:0.01Eu3+ are (0.6421, 0.3575), lies in the red region with 99.9 % color purity and have warm correlated color temperature (CCT) values. Therefore obtained results suggest that the prepared Mg(1-x)Ti2O5:xEu3+phosphors can be used as an efficient red phosphor for w-LED applications.

Structural, bandgap tailoring, photoluminescence and electrochemical characteristics of Sm3+-doped ZnS quantum dots prepared in Ar-atmosphere

Sm3+-doped ZnS quantum dots were prepared by a cost-effective, simple co-precipitation technique under an argon atmosphere. The prepared Sm3+-doped QDs exhibited a cubic structure with an average particle size of ∼ 2 nm, as confirmed through X-ray diffraction and high-resolution transmission electron microscopic investigations. The crystallite was reduced and strain produced due to the larger ionic radius of Sm3+ ions. The Sm (at. 2 %)-doped ZnS exhibited a blue shift, and the optical transmittance was enhanced. A highly intense red emission was obtained in photoluminescence investigations, and this is due to the transfer of photons from 4G5/2 → 6H11/2 for f-f transitions of the Sm3+ in the 4f5 configuration. The obtained photoluminescence emissions lead to red phosphor applications. The cyclic voltammogram analysis showed that adding Sm to ZnS QDs made their specific capacitance value higher and it found potential applications in supercapacitors.

A comparative study on the impact of cation replacements on the structural, optoelectronic and thermodynamic characteristics of hexafluorides red phosphors Cs2MF6 (M = C, Ge, Pb, Si) using first-principles calculations: a prospect for warm-white LEDs (w-LEDs) applications

A comparative study on the impact of cation replacements on the structural, optoelectronic and thermodynamic characteristics of hexafluorides red phosphors Cs2MF6 (M = C, Ge, Pb, Si) using first-principles calculations: a prospect for warm-white LEDs (w-LEDs) applications