Blue Light Excitation Research Articles

A novel Cr3+-doped MgGaBO4 phosphor: expanding the horizons in plant illumination

Near-infrared (NIR) spectroscopy technology has demonstrated unparalleled efficacy in night vision, iris authentication, plant illumination, food inspection, and various other domains. Nonetheless, the quest for novel phosphors exhibiting superior luminescent efficiency and enduring thermal stability persists as a formidable obstacle. In this study, phosphors MgGaBO4: Cr3+, Al3+ were successfully synthesized by high-temperature solid-phase reaction method. Firstly, starting from MgGaBO4: Cr3+, the crystal field environment around Cr3+ ions was modulated by replacing Ga3+ with Al3+ to further improve the luminescence performance of the phosphor. The emission peak wavelength of MgGaBO4: 0.0075Cr3+,0.005Al3+ phosphor was about 756 nm, the full width at half-maximum (FWHM) was about 174 nm under the blue light excitation of 440 nm. In addition, the luminescence intensity at 100 °C remains at 77.41% of that at room temperature. Finally, the excellent moisture resistance of this phosphor was demonstrated. This work not only introduces a novel broadband NIR phosphor with promising application potential in advanced agricultural lighting but also proposes a synergistic enhancement strategy for effectively improving the performance of broadband NIR phosphor-converted LED light sources.

Hypoxia-Active Iridium(III) Bis-terpyridine Complexes Bearing Oligothienyl Substituents: Synthesis, Photophysics, and Phototoxicity toward Cancer Cells.

In an effort to develop hypoxia-active iridium(III) complexes with long visible-light absorption, we synthesized and characterized five bis(terpyridine) Ir(III) complexes bearing oligothienyl substituents on one of the terpyridine ligands, i.e., nT-Ir (n = 0-4). The UV-vis absorption, emission, and transient absorption spectroscopy were employed to characterize the singlet and triplet excited states of these complexes and to explore the effects of varied number of thienyl units on the photophysical parameters of the complexes. In vitro photodynamic therapeutic activities of these complexes were assessed with respect to three melanoma cell lines (SKMEL28, A375, and B16F10) and two breast cancer cell lines (MDA-MB-231 and MCF-7) under normoxia (∼18.5% oxygen tension) and hypoxia (1% oxygen tension) upon broadband visible (400-700 nm), blue (453 nm), green (523 nm), and red (633 nm) light activation. It was revealed that the increased number of thienyl units bathochromically shifted the low-energy absorption bands to the green/orange spectral regions and the emission bands to the near-infrared (NIR) regions. The lowest triplet excited-state lifetimes and the singlet oxygen generation efficiency also increased from 0T to 2T substitution but decreased in 3T and 4T substitution. All complexes exhibited low dark cytotoxicity toward all cell lines, but 2T-Ir-4T-Ir manifested high photocytotoxicity for all cell lines upon visible, blue, and green light activation under normoxia, with 2T-Ir showing the strongest photocytotoxicity toward SKMEL28, MDA-MB-231, and MCF-7 cells, and 4T-Ir being the most photocytotoxic one for B16F10 and A375 cells. Singlet oxygen, superoxide anion radicals, and peroxynitrite anions were found to likely be involved in the photocytotoxicity exhibited by the complexes. 4T-Ir also showed strong photocytotoxicity upon red-light excitation toward all cell lines under normoxia and retained its photocytotoxicity under hypoxia toward all cell lines upon visible, blue, and green light excitation. The hypoxic activity of 4T-Ir along with its green to orange light absorption, NIR emission, and low dark cytotoxicity suggest its potential as a photosensitizer for photodynamic therapy applications.

High‐Stability Hybrid Antimony Halides for Thermometry in Power System Component or Circuit Monitoring

AbstractOrganic–inorganic metal halides (OIMHs) possess low preparation costs and high photoluminescence quantum yield. Within a specific range, the temperature‐dependent nature of OIMHs' luminescent lifetime facilitates temperature sensing and thermal imaging functionalities. In this study, a non‐toxic (C10H22N)6SbBr9·H2O ([C10H22N]+ is 4‐(tert‐buty)cyclohexanamine cation) with a 0D structure crystallized in the Pbcn space group is obtained. Under blue light excitation at room temperature, it demonstrates intense broad emission centered at 635 nm. Further investigation into the correlation between temperature and photoluminescence lifetime has unveiled exceptional temperature sensing precision. The relative sensitivities within the range of power system temperature alert 30–70 °C lie between 2.5% and 4.5% K−1. This matches the typical high‐temperature warning threshold for power systems. Moreover, after immersion in water and alcohol, the compound maintains remarkable stability, with multiple heating/cooling cycles confirming its reliability under test temperatures. Additionally, a composite thin‐film device composed of (C10H22N)6SbBr9·H2O, showcasing its potential as a stable and durable thermal imaging temperature sensing device is fabricated.

Efficient manipulation of photoluminescence by organic cations and Sb doping in hybrid manganese chlorides

Zero-dimensional (0D) Mn(II)-based hybrids with the typical d–d transitions have been rapidly developed benefitting from the environmental friendliness, blue light excitation and the high thermal stability. Herein, we first designed two novel green-emitting 0D Mn(II)-based hybrids (C16H28N)2MnCl4 and (C21H46N)2MnCl4, where the organic cations cocrystallize with four-coordinated [MnCl4]2- tetrahedrons. Upon blue-light excitation, these two crystals exhibited narrow-band green emission with distinct emission intensity and FWHM as well as thermal quenching behavior, which is analyzed by the influence of the crystal structure of different organic cations on the luminescence performance. Furthermore, multiple emission color can be observed from green to orange-red in (C16H28N)2MnCl4:Sb3+ by regulating the [SbCl5]2-/[MnCl4]2- molar ratio or excitation wavelength. Our study not only enriches the influence of organic cations on crystal structure and luminescence performance, but also provides a new direction towards realizing the multi-color emission by Sb3+ ions doping strategy.

Efficient Broadband Near‐Infrared Emitters in Lead‐Free Metal Halides with Record Photoluminescence Quantum Yield Under Blue Light Excitation

AbstractRealizing ultra‐efficient broadband near‐infrared (NIR) luminescence, especially under blue light excitation, remains an enormous challenge in lead‐free metal halides. Herein, the efficient NIR emission under blue light excitation is achieved in Sb3+‐doped 0D (ETPP)2ZnCl4xBr4‐4x (x = 0–1) (ETPP+ = (Ethyl)triphenylphosphonium) through coordination structure modulation and halogen substitution. Compared with the visible light emission of Sb(III)‐based compounds, the emission in Sb3+‐doped (ETPP)2ZnCl4xBr4‐4x shifts to the NIR region due to the large excited state lattice distortion. Parallelly, the excitation bands gradually shift from 376 to 450 nm as Br gradually replaces Cl, and the emission bands can further shift from 702 to 763 nm. Thus, the broadband NIR emission at 763 nm with a record luminous efficiency of 55.4% under 450 nm excitation can be achieved in Sb3+‐doped compounds. Moreover, the large‐scale synthesis technique of Sb3+‐doped (ETPP)2ZnBr4: NIR phosphors at room temperature is further developed and this compound exhibits impressive thermal and chemical‐stabilities. Finally, a high‐performance NIR light‐emitting‐diode is fabricated by combining a commercial blue chip and (ETPP)2ZnBr4:10%Sb3+ phosphors, which shows the most advanced photoelectric efficiency (17.8%) and output power (67.7 mW) in lead‐free metal halides. Thus, the as‐fabricated device is further demonstrated in the applications of night vision and biomedical imaging.

Effect of samarium oxide addition on the structural, thermal, and optical properties and photoluminescence of lithium borate glass

The samples were prepared in compliance with the form 33 Li2O–66 B2O3—(1-x) AgF—x Sm2O3, where x = 0, 0.25, 0.5, and 0.75. Powdered samples were converted to a glassy state via melting and quenching. The glassiness of the prepared samples was examined using X-ray diffraction (XRD) and Differential Thermal Analysis (DTA). From the absorption spectra of the prepared glass samples, the band gap in the optical spectrum changed slightly in the range of 3.45, whereas the Urbach energy decreased from 0.32 to 0.267 eV. The fluctuations of the optical band gap and Urbach energy can be attributed to variations in the glass structure. Sm3 + emitted intense reddish-orange light under blue and UV light excitation. There are six excitation bands in the Sm3+ excitation spectrum situated in the blue and UV regions, peaking at 361.7, 374, 400, 417, 462, and 475 nm, which are attributed to the transitions from 6H5/2 to 4D3/2, 6P7/2, 6P3/2, 6P5/2, 4I13/2, and 4I11/2 respectively. The transition from 6H5/2 to 6P3/2 had the highest intensity and was associated with a peak at 400 nm. The bright yellow, reddish-orange, and red emission bands of the Sm3+ ions in the oxide glasses are related to the 4G5/2 → 6H5/2, 4G5/2 → 6H7/2, and 4G5/2 → 6H9/2 emission transitions, respectively.

Rapid detection of murine-derived ingredients in meat products using real-time enzymatic recombinase amplification.

Accurate identification of meat species is critical to prevent economic fraud and safeguard public health. The use of inappropriate meat sources, such as murine, poses significant health risks because of potential contamination with pathogens and allergens, leading to foodborne illnesses. The present study aimed to develop a novel real-time enzymatic recombinase amplification (ERA) method for the rapid and specific detection of murine DNA in meat products. A novel ERA primer and probe set was designed, targeting a murine-specific single-copy nuclear gene identified through bioinformatics analysis. The assay demonstrates high specificity, showing no amplification in commonly consumed meats, other animals or major crops. Additionally, it exhibits remarkable sensitivity, detecting as few as five copies of murine genomic DNA. For practical application, the ERA method could effectively identify mouse DNA in laboratory-prepared samples at concentrations as low as 0.5% and also quantify samples with mouse DNA content as low as 5%. It also accurately detects the presence of murine-derived ingredients in commercially available meat products. The detection process is straightforward, utilizing a simple isothermal device for incubation, blue light excitation and a smartphone camera for result interpretation. This rapid analysis can be completed within 20 min. The newly developed real-time ERA method provides a valuable tool for standardizing meat trade practices, promoting food safety and enhancing consumer confidence in the authenticity of meat products. © 2024 Society of Chemical Industry.

Isomorphism of Sr[Li3AlO4] and Sr[Li3GaO4] - Syntheses, Crystal Structure, and Europium(II) Luminescence.

While highly efficient red-emitting inorganic phosphors have been discovered in the substance class of alkaline earth oxo(nitrido)lithoaluminates, new narrow-band green- and yellow-emitting components are being sought to improve the performance of phosphor-converted light-emitting diodes (pc-LEDs). Various solid-state reactions were carried out under protective gas atmosphere in nickel crucibles and sealed tantalum ampules to synthesize Sr[Li3AlO4], Sr[Li3GaO4], and five substitutional derivates of Sr[Li3(Al1-x Ga x )O4] at moderate temperatures. The observation of a linear increase in the unit cell parameters as a function of the increasing gallium mole fraction x in Sr[Li3(Al1-x Ga x )O4] revealed Vegard behavior in the solid-solution series, which was derived from powder X-ray diffraction data. The isomorphic crystallization of the new oxolithogallate Sr[Li3GaO4] and the known oxolithoaluminate Sr[Li3AlO4] in an ordered variant of the U[Cr4C4] aristotype was verified on the basis of powder and single-crystal X-ray diffraction data. Photoluminescence spectroscopy was used to investigate the narrow-band emissions in the substitution series of Eu2+-activated Sr[Li3(Al1-x Ga x )O4] under blue-light excitation. The emission maximum was shifted to higher energies as the gallium mole fraction increased. Peak wavelengths were observed at λem = 572 nm (fwhm equals 47 nm, 1446 cm-1, 0.18 eV) for yellow-emitting Sr[Li3AlO4]:Eu2+ and at λem = 554 nm (fwhm equals 49 nm, 1589 cm-1, 0.20 eV) for green-emitting Sr[Li3GaO4]:Eu2+. Sr[Li3AlO4]:Eu2+ has excellent thermal quenching resistance with a photoluminescence emission intensity of >93% at T = 423 K relative to the room temperature value, making this inorganic phosphor a potential candidate for solid-state lighting applications.

A novel Mn4+-doped Li2Mg4TiO7 red-emitting phosphor for warm white light-emitting diodes

To improve the light quality of warm white-LEDs (w-LEDs), novel Mn4+-activated red-emitting phosphors that can be excited efficiently by blue light with yield high performance are highly imperative. Here, we report a Mn4+-doped Li2Mg4TiO7 (LMT) phosphor prepared via a traditional high-temperature reaction method. The crystal structure and luminescent properties of the LMT:Mn4+ phosphors are studied. An excitation band centered at 470 nm, matches well with the commercial blue LED chips. Upon blue light excitation, a broadband red emssion located at 673 nm due to d-d transitions of Mn4+ is observed. The optimum doping concentration of Mn4+ is determined to be x = 0.08 %. The optimized red-emitting phosphor LMT:Mn4+ attains a photoluminescence quantum yield (PLQY) of 40.0 % and a good thermal resistance (ΔE = 0.43 eV). The combination of the as-obtained red-emitting phosphor, commercially available yellow phosphor, and blue LED chip yields a warm w-LED device, delivering CIE (x, y) = (0.3922, 0.3909), CRI = 70.0 and CCT = 2214 K. Therefore, this work provides a novel LMT:Mn4+ phosphor as a potential red component for warm w-LEDs.

Highly efficient and water-resistant BaGa4S7:Eu2+ phosphor prepared by a self-reduction method

The development of eco-friendly luminescent materials is imperative for the advancement of phosphor-based technologies. This study corroborates the self-reduction of Eu3+ to Eu2+ through analyses utilizing photoluminescence (PL), excitation spectroscopy (PLE), and X-ray photoelectron spectroscopy (XPS). Density functional theory (DFT) calculations demonstrate that Eu2+ ions can efficaciously substitute Ba2+ ions within the BaGa4S7 lattice, preserving its structural integrity. Upon blue light excitation, BaGa4S7:Eu2+ manifests a robust green emission attributed to Eu2+ ions, showcasing a peak wavelength near 526 nm. The quantum yield (QY) of BaGa4S7:Eu2+ is remarkably high, registering at 74.8 %. Moreover, the temperature-dependent luminescence properties of BaGa4S7:Eu2+ phosphor were subjected to thorough investigation. Water resistance assays indicate that the sample preserves 76 % of its initial luminous intensity following 40 days of aqueous immersion. Additionally, BaGa4S7:Eu2+ based phosphor-converted white light-emitting diodes (WLEDs) demonstrate emission of high-quality white light. This unique water-resistant green emission sulfide phosphor is expected to have potential applications in lighting fields.

Enhancing blue light excitation in Pb-free double perovskites by decreasing the energy barrier of the self-trapping exciton and prospects for environment-friendly optoelectronic applications

In Pb-free double perovskites (DPs) optoelectronic material systems, the energy barrier ∆Eb suppression between free excitons (FEs) and self-trapped excitons (STEs) makes it difficult to achieve blue-light excitation even as the bandgap narrows, which has become a major challenge in the development of full-colour displays, lighting, optoelectronics and catalytic technologies. Here, Cs2-aKaAg0.6Na0.4In0.8Bi0.2Cl6-x-yBrx(SH)y DPs, prepared by doping with HS- (hydrosulfide ion), Br- and K+, achieve a blue excitation at 468 nm. The octahedral tilt caused by doping with K+, Br- and HS- ions reduces the local crystal dimensions and thus the energy barrier ∆Eb. The aggregation of electrons around the AgX6 octahedron under the action of HS- contributes to the formation of effective STE emission under blue light excitation. Furthermore, the potential impact of blue-light-excited Cs2-aKaAg0.6Na0.4In0.8Bi0.2Cl6-x-yBrx(SH)y DPs on enhancing the power conversion efficiency (PCE) of photovoltaic modules and the photodegradation efficiency of Rhodamine B (RhB) is explored. The study concludes by highlighting the wide-ranging applications in displays, photovoltaics, and photocatalytic degradation that could be realized through the utilization of blue-light-excited Pb-free DPs.

Evaluation of antimicrobial photodynamic activity of CuminUP60®- A commercially-available high-soluble curcumin

Curcumin, a polyphenol extracted from Curcuma longa L. with a variety of biological and pharmacological activities, has been identified as a promising photosensitizer for food sterilization. However, its low aqueous solubility and bioavailability greatly restrict the practical application of curcumin. In the last decades, a number of approaches have been proposed to address this challenge, with several having already attained notable commercial viability. CuminUP60®, a patented curcumin complex consisting of curcumin extract and Poloxam407, has gathered attention in commercial realms for its enhanced solubility, bioavailability and therapeutic potential. However, the antimicrobial photodynamic activity of this novel curcumin complex has not been investigated. In the current study, we found that CuminUP60® showed a maximum absorption intensity at 434 nm with capability to produce Reactive Oxygen Species (ROS) upon blue light excitation. Furthermore, CuminUP60® showed desirable bactericidal activity against a range of typical foodborne bacteria including Staphylococcus aureus, Listeria monocytogenes Vibrio parahaemolyticus, Shewanella putrefaciens, Pseudomonas fluorescens (MIC = 83.33 μM) and Escherichia coli (MIC = 166.66 μM) upon blue light (5.3 mW/cm2) illumination for 30 min. Taken together, the results demonstrated that CuminUP60® possess desirable antibacterial photodynamic activity, which could provide crucial support for the development of industrially applicable photodynamic sterilization systems within the food industry.

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.

Blue‐Light‐Excitable Broadband Ca3Ga2Ge3O12:Cr3+,Ni2+ Phosphor for the Applications in NIR‐II Window

AbstractNear‐infrared (NIR) phosphor‐converted light‐emitting diode (pc‐LED) light sources in the second NIR window (NIR‐II, 1000–1700 nm) have sparked great interest for their emerging applications in non‐destructive detection and medical diagnostics fields. However, the development of efficient NIR‐II phosphors that can be excited by commercial blue LED chips remains a significant challenge, and thus impeding the applications of NIR pc‐LED. Herein, a blue‐light‐excitable broadband NIR‐II luminescence of Ni2+ is achieved upon incorporating Cr3+ and Ni2+ into the Ca3Ga2Ge3O12 (CGGO) host simultaneously. Through the energy transfer from Cr3+ to Ni2+, CGGO:Cr3+,Ni2+ phosphor presents the improved NIR‐II emission peaking at 1470 nm under 460 nm blue light excitation. The internal/external quantum efficiency values are significantly improved from 13.8%/3.3% to 24.6%/13.3% along with the enhanced luminescence thermal stability. Finally, a NIR pc‐LED is fabricated by combining CGGO:Cr3+,Ni2+ phosphor with 450 nm blue chip, and its potential applications in non‐destructive examination and biomedical imaging fields have been demonstrated. The strategy of Cr3+ and Ni2+ co‐doping solves the problem that Ni2+ luminescence cannot be effectively excited by blue light and provides the design insights to exploit more ultra‐broadband NIR pc‐LEDs based on blue LED chips.

Two-Stage Mixed-Dye-Based Isothermal Amplification with Ribonuclease-Cleavable Enhanced Probes for Dual-Visualization Detection of SARS-CoV-2 Variants of Interest.

Rapid and visual detection of SARS-CoV-2 variants is vital for timely assessment of variant transmission in resource-limited settings. Here, a closed-tube, two-stage, mixed-dye-based isothermal amplification method with ribonuclease-cleavable enhanced probes (REP), termed REP-TMAP, for dual-visualization detection of SARS-CoV-2 variants including JN.1, BA.2, BA.4/5, and Delta is introduced. The first stage of REP-TMAP is reverse transcription recombinase polymerase amplification and the second stage is dual-visualization detection synergistically mediated by the REP and the mixed dyes of cresol red and hydroxy naphthol blue. In REP-TMAP reaction, the color change under ambient light indicates SARS-CoV-2 infection, while the fluorescence change under blue light excitation specifies variant type. On detecting transcribed RNA of SARS-CoV-2 spike gene, this assay is rapid (within 40min), highly sensitive (10-200 copies per reaction), and highly specific (identification of single-base mutations). Furthermore, the assay has been clinically validated to accurately detect JN.1, BA.2, and BA.4/5 variants from 102 human oropharyngeal swabs. The proposed assay therefore holds great potentials to provide a rapid, dual-visualization, sensitive, specific, point-of-care detection of SARS-CoV-2 variants and beyond.

Synthesis and luminescent properties of highly thermally stable GdGa3(BO3)4:Cr3+ broadband near-infrared phosphors for near-infrared LED applications

Developing near-infrared (NIR) phosphors with high thermal stability and broadband emission is pivotal for advancing NIR light sources. In this study, we synthesized a novel borate phosphor, GdGa3(BO3)4:Cr3+, via a high-temperature solid-state reaction. This phosphor demonstrates exceptional thermal stability, maintaining 94 % of its initial intensity even at 150 °C. Upon blue light excitation, it emits a broad spectrum from 650 to 1100 nm, peaking at 770 nm with a full width at half maximum (FWHM) of ∼130 nm. We conducted a comprehensive investigation to understand the mechanisms underlying its thermal stability. Additionally, by combining the GdGa3(BO3)4:15%Cr3+ phosphor with a commercial blue light chip, we fabricated an NIR LED device achieving a NIR output power of 6.45 mW and a photoelectric conversion efficiency of 1.57 % at 120 mA. This study offers valuable insights into the design of advanced NIR phosphors with superior thermal stability for NIR light source applications.

Highly efficient blue-light-excitable ultra-broadband orange-emitting Mg2.5Y1.5Al1.5Si2.5O12:Ce3+ garnet phosphors for solid-state lighting

Lighting and display technologies are revolutionized by the invention of YAG:Ce3+ phosphors driven by InGaN blue light-emitting diode (LED). Yet, the faint emission components in the red spectral region from typical LED devices can cause circadian rhythm disorders and aesthetic fatigue of the human eye. Developing broadband orange-emitting phosphor with abundant red coverage is one of the approaches for addressing this challenging problem. Herein, an innovative ultra-broadband orange-emitting Mg2.5Y1.5Al1.5Si2.5O12:Ce3+ (MYASO:Ce3+) garnet phosphor is successfully reported to bridge the above gap. The representative MYASO:4%Ce3+ sample exhibits an unexpectedly luminescence band with the full width at half maximum (FWHM) of up to 155 nm, the high thermal robustness (58%@423 K), and satisfactory internal quantum efficiency of 67% upon 465 nm blue light excitation. Such a large FWHM value results from the occupation of a single crystallographic site of Ce3+ in the dodecahedral [YO8] position of MYASO garnet host. Red-shift emission with respect to commercial YAG:Ce3+ is mainly attributed to the cooperative effect of the enhanced crystal field strength and increased Stokes shift. The emission intensity reduction at the high-temperature environment of MYASO:4%Ce3+ is derived from the enhancement of the thermal cross-relaxation associated with the larger Stokes shift (4839 cm−1). The resulting high-quality warm white LED device fabricated from the optimal MYASO:4%Ce3+ sample shows a satisfactory color rendering index (CRI = 84), comfortable correlated color temperature (CCT = 4032 K) and an excellent luminous efficacy (LE = 58.7 lm W−1) under a 60 mA drive current. These findings stimulate the exploration of ultra-broadband orange-emitting phosphors with abundant red emission to fabricate high-CRI warm-white LEDs for healthy solid-state lighting.

Broadband Yellow-Emitting Oxynitride Phosphor Sr2Si7Al3ON13:Ce3+,Eu2+ for White Light-Emitting Diodes with a High Color Rendering Index.

The utilization of blue LED chips in conjunction with the commercial yellow phosphor YAG:Ce3+ currently represents the most straightforward and efficient approach for generating white light, albeit at a slight compromise to the color rendering index. However, by expansion of the spectral coverage of the yellow phosphor, it becomes feasible to achieve a high color rendering index for white light. In this study, we synthesized a broadband yellow oxynitride phosphor through codoping Ce3+ and Eu2+ on highly chemically stable Sr2Si7Al3ON13. We conducted an extensive investigation of the energy transfer process between Ce3+ and Eu2+ within Sr2Si7Al3ON13:Ce3+,Eu2+. By adjusting the doping concentration of Eu2+, we successfully obtained a higher emission intensity and improved thermal stability for Sr2Si7Al3ON13:Ce3+,Eu2+ under 450 nm blue-light excitation. Furthermore, we achieved a full width at half-maximum (fwhm) broadened to 130 nm along with an optimal external quantum efficiency (EQE) of 43.2%. The resulting WLED devices utilizing this yellow phosphor exhibited high color rendering index (CRI, Ra = 86.2) white light emission (0.3488, 0.3407). These exceptional properties highlight the significant potential application of Sr2Si7Al3ON13:Ce3+,Eu2+ in blue light-excited WLED as well as its promising prospects in indoor display lighting.

A new yellowish‐green‐emitting phosphor: Eu2+‐doped Ba3YAl2O7.5

AbstractA yellowish‐green emitting phosphor Ba3YAl2O7.5:Eu2+ was synthesized by a solid‐state method. The crystal structure, luminescence, concentration quenching, fluorescence decay, and thermal quenching properties were systematically investigated. Under blue light (440 nm) excitation, Ba3YAl2O7.5:Eu2+ phosphors exhibit a yellowish‐green emission peaking at 550 nm with a full width at half maximum ∼ 69 nm, and The Commission Internationale de l'Eclairage (CIE) coordinates of Ba3YAl2O7.5:Eu2+ are (0.4064, 0.5811). Structural analysis and Van Uitert equation along with fluorescence lifetime analysis reveal that Eu2+ ions occupy 6‐coordinated Y and 9‐coordinated Ba sites in Ba3YAl2O7.5, and therefore generate two emission sub‐bands at 582 and 548 nm. In addition, Ba3YAl2O7.5:Eu2+ phosphor remaining 43% photoluminescence emission intensity at 125°C with an activation energy of 0.372 eV. Utilizing the title phosphor (Ba3YAl2O7.5:3%Eu2+), commercial red (Ca,Sr)AlSiN3:Eu2+ (CSAlSi:Eu2+) phosphor, and InGaN‐based blue light emitting diode (LED) chip, a proof‐of‐concept warm white LEDs (WLEDs) with a color rendering index of 80.1, CIE chromaticity coordinates of (0.411, 0.381), luminous efficacy of ∼ 22.13 lm/W, and correlated color temperature of ∼ 3288 K is achieved. Thus, Eu2+ activated Ba3YAl2O7.5 phosphors have the potential application in WLEDs pumped by a blue LED chip for solid‐state lighting application.

Solid solution structural engineering enhances the luminescence of SrMgAl10O17:Cr3+ for agricultural lighting

Lead-free non-rare earth oxide phosphors have attracted wide attention due to their environmental protection, sustainability, and potential to replace halides and fluorides in the field of plant lighting. Among them, the Cr3+-excited aluminate phosphor exhibits high brightness, high thermal stability, and far red to near-infrared (NIR) emission due to the influence of the crystal field strength (CFS). This property gives rise to a variety of strategies used to modulate the CFS, for example, single ion substitution, chemical unit co-substitution, etc. Here, we chose the substitution of a single ion, with [BaO6] gradually replacing [SrO6] to form a solid solution. Their structural characteristics and the local structure of Cr3+ are studied and discussed. The device is packaged to evaluate the feasibility of the material for practical application. The prepared phosphor had a bright far-red light emission of 693 nm under blue light excitation, and this spectrum strongly matched the absorption of plant phytochrome PFR. This work provides the design principle of far red light emission activated by Cr3+ aluminate solid solution, which can inspire further research on pc-LED lights for plant lighting.