Blue Light-emitting Diode Chip Research Articles

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.

The synthesis and properties of Ca3 Sc2 Si3 O12 :Ce3+ (CSSG) phosphor are utilized for the development of human-centric lighting light-emitting diodes (HCL-LEDs).

In this study, cerium ion (Ce3+ )-doped calcium scandium silicate garnet (Ca3 Sc2 Si3 O12 , abbreviated CSSG) phosphors were successfully synthesized using the sol-gel method. The crystal phase, morphology, and photoluminescence properties of the synthesized phosphors were thoroughly investigated. Under excitation by a blue light-emitting diode (LED) chip (450 nm), the CSSG phosphor displayed a wide emission spectrum spanning from green to yellow. Remarkably, the material exhibited exceptional thermal stability, with an emissivity ratio at 150°C to that at 25°C reaching approximately 85%. Additionally, the material showcased impressive optical performance when tested with a blue LED chip, including a color rendering index (CRI) exceeding 90, an R9 value surpassing 50, and a biological impact ratio (M/P) above 0.6. These noteworthy findings underscore the potential applications of CSSG as a white light-converting phosphor, particularly in the realm of human-centered lighting.

Structural, optical and photoluminescence properties of BaLa2ZnO5: Eu3+ phosphor: A prospective red-emitting phosphor for LED applications

Herein, we report the synthesis of red-emitting Eu3+-activated BaLa2ZnO5 phosphors using a high-temperature solid-state reaction technique. The phase confirmation and crystal structure were established through X-ray powder diffraction patterns. Density-functional theory calculations revealed an indirect bandgap in the material. The bandgaps of both undoped and doped BaLa2ZnO5 phosphors were analyzed using diffuse reflectance spectra. The influence of Eu3+ doping on the bandgap was confirmed by applying the Kubelka-Munk function to the diffuse reflectance spectra. The effects of doping on the surface morphology and elemental composition were investigated through field emission scanning electron microscopy and energy-dispersive spectroscopy, respectively. Additionally, X-ray photoelectron spectroscopic studies were conducted to analyze the electronic structure, chemical states and impact of doping on the crystal structure. Using near ultraviolet excitation at 329 nm, the synthesized phosphor exhibited strong red emission attributed to various 5D0 → 7FJ transitions. Concentration quenching phenomena were observed due to dipole-dipole interactions. Judd-Ofelt analysis was performed to elucidate the coordination nature of the doping element in the host lattice. Excellent thermal stability was observed with an activation energy of 0.64 eV for discharging via lattice vibrations. The better color purity (98–99.3 %) and stable Commission Internationale de l’Elcairage coordinates in the red region of the gamut suggest that the prepared phosphor material holds potential as an efficient candidate for ultra violet and blue light-emitting diode chips, as well as an efficient component in the fabrication of white light-emitting diodes.

Ultra-fast fabrication of phosphor in glass via laser sintering using silicon wafers

One of the essential components for fabricating high-power-driven light-emitting diodes (LEDs) is phosphor in glass (PiG). Mixing, sintering, and polishing are necessary for this PiG fabricating technique for the blue LED to function as a light converter. However, oxidation of the phosphor during the sintering process result in degradation, and the yield lowers during the polishing stage. Here we suggest a laser sintering method to fabricate the PiG that has the advantages of a shorter process time and an increased yield. The quick processing time may inhibit the phosphor oxidations, and the Si wafer effectively inhibits bending during the laser sintering. Utilizing silicon wafers is the key to making the process practically usable. Testing on blue LED chips with 250 mA operating currents demonstrates sufficient performance for a PiG photoconverter fabricated using this laser sintering approach. The suggested technique can contribute to the development of the PiG industry due to its high efficiency.

High-Efficiency Narrow-Band Green-Emitting Manganese(II) Halide for Multifunctional Applications.

Zero-dimensional (0D) Mn2+-based metal halides used as luminescent materials and scintillators have become a research hotspot in the field of photoelectric materials and devices due to their unique composition, structure, and fluorescence properties. It is of great value to explore new Mn2+-based metal halides to achieve multifunctional applications. Herein, the novel 0D Mn2+-based metal halide single crystal (BPTP)2MnBr4 is synthesized by a simple solvent-antisolvent recrystallization method. Under excitation at 468 nm, the (BPTP)2MnBr4 single crystal shows a pronounced narrow-band green luminescence centered at 515 nm derived from the d-d transition of the Mn2+ ion. This emission has a relatively narrow full width at half maximum of 43 nm and a high photoluminescence quantum yield (PLQY) of 82%. In addition, (BPTP)2MnBr4 exhibits good thermal stability at 393 K with a retention of 79% of the initial photoluminescence intensity at 298 K. Benefiting from its strong blue light excitation, high PLQY, and good thermal stability, we manufacture an ideal white light-emitting diode (LED) device using a 460 nm blue LED chip, green-emitting (BPTP)2MnBr4, and commercial K2SiF6:Mn4+ red phosphor. Under 20 mA drive current, the LED shows a high luminous efficiency of 112 lm/W and a wide color gamut of 110.8%, according to the National Television System Committee standard. In addition, (BPTP)2MnBr4 crystals show a strong X-ray absorption. Based on the commercial Lu3Al5O12:Ce3+ scintillator, the calculated light yield of (BPTP)2MnBr4 reaches up to about 136,000 photons/MeV and the detection limit reaches 0.282 μGyair s-1. Additionally, a melt quenching approach is used to construct a (BPTP)2MnBr4 clear glass scintillation screen, realizing a spatial resolution of 10.1 lp/mm. The proper performances of (BPTP)2MnBr4 as phosphor-converted LED materials and the X-ray scintillator with the addition of eco-friendly, low-cost solution processability make 0D Mn2+-based metal halides potential luminescent materials for multifunctional applications.

Luminescence characteristics of ultra-broadband near-infrared emission Li3Mg2SbO6:Cr3+ phosphors and their applications in light-emitting diodes

In this study, a Li3Mg2SbO6:Cr3+ phosphor was prepared by high-temperature solid-phase reaction. The phosphors doped with 0.03Cr3+ showed broadband emission at 805 nm, a wide spectral band of 200 nm at 435 nm excitation, an internal quantum efficiency of 80.8%, and the integrated emission intensity at 423 K of Li3Mg2SbO6:Cr3+ is about 50% of that at room temperature. The phosphors conversion (pc) - light-emitting diodes (LEDs) with broadband near-infrared (NIR) emission were prepared using the Li3Mg2SbO6:Cr3+ phosphor coating on blue LED chips. They achieved 10.4% photoelectric efficiency and 60.2 mW NIR output power at 210 mA. All results showed that the Li3Mg2SbO6:Cr3+ phosphors had considerable potential in NIR spectroscopy applications.

Efficient blue-light-excited cyan-emitting CaLu2HfScAl3O12:Ce3+ phosphors for full-visible-spectrum warm-white LEDs

Bright cyan-emitting phosphor is indispensable to fill the cyan gap for the fabrication of full-visible-spectrum warm-white light-emitting diodes (LEDs) with high color rendering index (CRI). In this study, we demonstrate a novel efficient cyan-emitting Ce3+-activated CaLu2HfScAl3O12 (CLHSA) garnet phosphor for application in blue-light-excited full-spectrum warm-white LEDs. CLHSA:Ce3+ phosphors show broadband excitation spectra in the 300–470 nm spectral range with a maximum peak at 408 nm, indicating they can be efficiently pumped by the blue LED chips. The optimal doping concentration of Ce3+ ions is found to be 1 mol%. Upon 408 nm excitation, the optimal CLHSA:1%Ce3+ phosphor gives rise to a bright broadband cyan emission (peak position: 498 nm; bandwidth: 97.5 nm) with CIE chromaticity coordinates of (0.2196, 0.4265) and high photoluminescence quantum yield of 64.5%. Finally, we have fabricated a blue-light-excited high-CRI warm-white LED device by employing the CLHSA:1%Ce3+ cyan phosphor, commercial YAG:Ce3+ yellow phosphor and commercial CaAlSiN3:Eu2+ red phosphor as well as a 450 nm LED chip, which demonstrates a bright warm-white light emission with a high CRI (Ra = 92.6), a low correlated color temperature (3660 K), and good CIE chromaticity coordinates of (0.3993, 0.3939) as well as a high luminous efficacy of 45 lmW−1. Therefore, this newly discovered efficient cyan-emitting CLHSA:1%Ce3+ phosphor is promising for application in blue-chip-pumped full-visible-spectrum warm-white LEDs with high CRI values.

Broadband Short-Wave Infrared-Emitting MgGa2O4:Cr3+, Ni2+ Phosphor with Near-Unity Internal Quantum Efficiency and High Thermal Stability for Light-Emitting Diode Applications.

Blue InGaN chip-pumped short-wave infrared (SWIR) emitters have aroused tremendous attention and shown emerging applications in diverse fields such as healthcare, retail, and agriculture. However, discovering blue light-emitting diode (LED)-pumped SWIR phosphors with a central emission wavelength over 1000 nm remains a significant challenge. Herein, we demonstrate the efficient broadband SWIR luminescence of Ni2+ by simultaneously incorporating Cr3+ and Ni2+ ions into the MgGa2O4 lattice, with Cr3+ as the sensitizer and Ni2+ as the emitter. Because of the strong blue light absorption of Cr3+ and high energy transfer efficiency to Ni2+, the obtained MgGa2O4:Cr3+, Ni2+ phosphors show intense SWIR luminescence with a peak wavelength at 1260 nm and a full width at half maximum (FWHM) of 222 nm under the excitation of blue light. The optimized SWIR phosphor presents an ultra-high SWIR photoluminescence quantum efficiency of 96.5% and outstanding luminescence thermal stability (67.9%@150 °C). A SWIR light source has been fabricated through a combination of the prepared MgGa2O4:Cr3+, Ni2+ phosphor and a commercial 450 nm blue LED chip, delivering a maximum SWIR radiant power of 14.9 mW at 150 mA input current. This work not only demonstrates the feasibility of developing broadband high-power SWIR emitters using converter technology but also presents new insights into the importance of SWIR technology.

Broadband near infrared luminescent properties of Cr3+ activated SrGa2Si2O8 phosphor

There has been a lot of interest in trivalent chromium ion-doped phosphors for near-infrared (NIR) luminescence in recent years. Here, trivalent chromium-doped NIR emitting SrGa2Si2O8 phosphors were synthesized. The electronic structure was calculated via density functional theory. Although only [SrO7], [SiO4], and [GaO4] polyhedra were found in the host, we still observe broadband luminescence of Cr3+ in the region of 650–950 nm from octahedra site. Due to the doping of Cr3+, a transformation from [GaO4] tetrahedron rearrange into [CrO6] octahedron was produced. The experimental results of X-ray photoelectron spectroscopy and electron paramagnetic resonance spectroscopy demonstrated the presence of Cr3+. A systematic study of the photoluminescence properties of SrGa2Si2O8:Cr3+ was conducted. The luminescent intensity of SrGa2Si2O8:0.005Cr3+ at 420 K can be retained at 83.42% compared to 300 K, indicating its high thermal stability. The electroluminescence of the prepared light emitting diode (LED) based on SrGa2Si2O8:Cr3+ and blue LED chip was measured under various currents. The application as a NIR LED light source was demonstrated in human hands.

Highly efficient far-red emitting Mn4+-activated Li3La3W2O12 phosphors for plant growth LED lighting

High-efficiency far-red emitting phosphors with an emission peak of around 730 nm are urgently needed for indoor plant growth light-emitting diode (LED) lighting. In this article, we report on the synthesis, crystal structure, and luminescence properties of a new highly efficient Mn4+ ion-activated Li3La3W2O12 (LLWO) far-red emitting phosphor. A group of LLWO:Mn4+ phosphors doped with different Mn4+ ion concentrations have been prepared via the conventional high-temperature solid-state reaction route. X-ray diffraction Rietveld refinement reveals that the LLWO:Mn4+ phosphor has the monoclinic structure with space group P21/n, along with lattice parameters of a = 5.5396 Å, b = 5.6026 Å, c = 7.8802 Å, α = γ = 90°, β = 90.0988°, and V = 244.57 Å3. Interestingly, LLWO:Mn4+ phosphors can generate bright narrowband far-red emission in the 650–800 nm wavelength range peaking at 719 nm due to the spin- and parity-forbidden 2Eg→4A2g transition of Mn4+ ions, matching well with the absorption spectrum of phytochrome PFR. The excitation spectrum monitored at 719 nm has a broad excitation band with the range from 250 to 550 nm centered at 339 nm and 472 nm, indicating that LLWO:Mn4+ phosphors could be efficiently pumped by both ultraviolet and blue LED chips. The highest far-red emission is achieved for the sample doped with 1.2 mol% Mn4+ ion, and this optimal LLWO:1.2%Mn4+ sample shows a high internal quantum efficiency of 88.4% and a decay lifetime of 2.289 ms. Commission Internationale de l’Eclairage (CIE) color coordinates of LLWO:1.2%Mn4+ are determined to be (0.7326, 0.2674). Besides, the crystal field analysis and temperature-dependent emission spectra of the as-prepared samples have been investigated in detail. The emission intensity of LLWO:1.2%Mn4+ sample at 423 K remains about 40% of that at 303 K. Finally, a LED device is fabricated by integrating the LLWO:1.2%Mn4+ phosphors and a 460 nm blue LED chip, which shows bright blue and far-red dual emission bands under 20–300 mA driving currents. This work demonstrates that these newly developed far-red emitting LLWO:Mn4+ phosphors have excellent application prospects in plant growth LED lighting.

High luminous efficiency of a phosphor-in-glass plate by optimization of the glass and phosphor content for high-power LED applications

Generally, white light-emitting diodes (LEDs) are fabricated by combining blue LED chips with yellow phosphors. When fabricating white LEDs, the phosphor is typically mixed with an organic resin and applied to the LED chips as a paste. A phosphor-in-glass (PiG) plate can alternatively be used to address the poor high-temperature reliability of the paste method. However, because pores form in the PiG plate during the sintering process, this method results in a loss of optical efficiency. Accordingly, we aimed to improve the fluidity of glass and light efficiency by optimizing the sintering temperature of the glass powder and the phosphor content respectively for reducing internal porosity in the PiG. In this study, glass powder was sintered at different temperatures to produce glass plates, while also varying the phosphor content to fabricate PiG plates. The optimal light characteristics were realized with a glass sintering temperature of 640 °C and a phosphor content of 20 wt%.

Realizing Wide‐Gamut Human‐Centric Display Lighting with K3AlP3O9N:Eu2+

AbstractComputers, televisions, and smartphones are revolutionized by the invention of InGaN blue light‐emitting diode (LED) backlighting. Yet, continual exposure to the intense blue LED emission from these modern displays can cause insomnia and mood disorders. Developing “human‐centric” backlighting that uses a violet‐emitting LED chip and a trichromatic phosphor mixture to generate color images is one approach that addresses this problem. The challenge is finding a blue‐emitting phosphor that possesses a sufficiently small Stokes’ shift to efficiently down‐convert violet LED light and produce a narrow blue emission. This work reports a new oxynitride phosphor that meets this demand. K3AlP3O9N:Eu2+ exhibits an unexpectedly narrow (45 nm, 2206 cm−1), thermally robust, and efficient blue photoluminescence upon violet excitation. Computational modeling and temperature‐dependent optical property measurements reveal that the narrow emission arises from a rare combination of preferential excitation and site‐selective quenching. The resulting chromaticity coordinates of K3AlP3O9N:Eu2+ lie closer to the vertex of the Rec. 2020 than a blue LED chip and provides access to ≈10% more colors than a commercial tablet when combined with commercial red‐ and green‐emitting phosphors. Alongside the wide gamut, tuning the emission from the violet LED and phosphor blend can reduce blue light emissions to produce next‐generation, human‐centric displays.

Site-Selective Occupancy Control of Cr Ions toward Ultrabroad-Band Infrared Luminescence with a Spectral Width up to 419 nm.

Infrared-emitting phosphor-converted light-emitting diodes (LEDs) are desirable light sources for a very wide range of applications such as spectroscopy analysis, nondestructive monitoring, covert information identification, and night-vision surveillance. The most important aspect of infrared emitters for spectroscopy is to cover the widest possible wavelength range of emitted light. However, developing ultrabroad-band infrared emitters based on converter technology is still a challenging task due to the lack of suitable phosphor materials that emit in a wide wavelength range upon excitation from blue-emitting chips. Herein, this work demonstrates Cr3+-activated Mg2SiO4 infrared phosphors with a super wide infrared spectral range of 600 to 1400 nm and high internal quantum yield up to 80.4% upon 460 nm excitation. Site-selective occupancy of Cr3+ emitters in two different Mg sites in the Mg2SiO4 lattice results in two distinct broad emission bands peaking at 760 and 970 nm, both of which contribute to the ultrabroad-band infrared luminescence with a full width at half maximum (FWHM) of 419 nm. This is by far the broadest infrared emission to the best of our knowledge. On this basis, an ultrabroad-band infrared LED prototype has been fabricated by the combination of the Mg2SiO4:Cr3+ phosphor with a blue LED chip, which shows great potential for imaging and sensing applications. This work demonstrates that site-selective occupancy control of Cr ions is an effective strategy for developing ultrabroad-band Cr3+-doped phosphors.

Site-selective occupation of Cr3+ ions toward ultra-broadband near-infrared emission stannate phosphors

Cr3+-activated near-infrared (NIR) luminescent materials with broadband emission have attracted extensive attentions for multipurpose NIR phosphor-converted light-emitting diodes (LED). It is widely believed that broadband NIR-emitting from optical center Cr3+ could merely made in crystal-filed caused six-coordinated sites or four-coordinated sites. Herein, taking La3Ga5SnO14 compound with six-coordinated Sn and four-coordinated Ga sites as host, we design and synthesize a new ultra-broad NIR-emitting La3Ga5Sn1-xO14:xCr3+ (LGSn1-x:xCr3+) phosphor ranging from 700 to 1500 nm via solid-state reaction. Structural analysis, low-temperature spectra investigations, and density functional theory calculations demonstrate that, in La3Ga5SnO14 (LGSn) host lattice, six-coordinated Sn sites and four-coordinated Ga sites can be successfully occupied by Cr3+ ions, leading to two distinct Cr3+ centers and an impressive broadband with full width at half maximum of up to 275 nm. At 373 K, emission intensity of LGSn0.97:3%Cr3+ phosphor maintains 43% of that at room temperature. We fabricate a NIR phosphor-converted LED device by using as-prepared LGSn0.97:3%Cr3+ phosphor and a blue LED chip and demonstrate its potential applications in night vision and food analysis. These findings provide not only an in-deep insight on site-occupation of Cr3+ residing in compounds with six-coordinated sites and four-coordinated sites but also feasible method of designing ultra-broadband NIR phosphors.

Excellent Quantum Efficiency and Superior Color Purity Red-Emitting CaAl12O19–CaAl4O7–MgAl2O4:Mn4+ Phosphors for Plant Growth and High Color Rendering Index White Light-Emitting Diode Applications

This work reports an excellent quantum efficiency and superior color purity CaAl12O19–CaAl4O7–MgAl2O4:Mn4+ (CCM:Mn4+) red-emitting phosphor. This phosphor can be excited by a broad excitation band ranging from 300 to 500 nm, and it generates an intense broadband red emission peaking at 656 nm. The CCM:0.5%Mn4+ phosphor-possessed superior color purity of 100%, a long lifetime of 0.49 ms, and high activation energy of 0.286 eV. Four different prototypes of plant growth light-emitting diodes (LEDs) with high quantum efficiencies of 81.8, 72.1, 67.2, and 61.1% were fabricated by coating the optimized CCM:0.5%Mn4+ phosphors onto UV (365 nm), NUV (395 nm), violet (410), and blue (460 nm) LED chips, respectively. The 81.8% and 72.1% QE values are the highest values reported for the 365 nm UV-pumped and 395 nm NUV-pumped LEDs based on Mn4+-doped oxide phosphors. Furthermore, a white LED with a high color rendering index (CRI) of 90, correlated color temperature (CCT) of 2416 K, and luminous efficacy of radiation (LER) of 216 lm/W was realized using a blue LED chip and a mixture of CCM:0.5%Mn4+ and commercial YAG:Ce3+ phosphors. Our results demonstrate great potential for using CCM:Mn4+ phosphors for plant growth LEDs and white light-emitting diode (WLED) applications.

Efficient Broadband Near-Infrared CaMgGe2O6:Cr3+ Phosphor for pc-LED.

Broadband near-infrared (NIR) phosphor-converted light-emitting diodes (pc-LEDs) are essential to integrate near-infrared spectrometers into mobile devices for the rapid and noninvasive detection of biological components. However, efficient broadband NIR phosphors with a peak emission wavelength longer than 800 nm are deficient. In this study, CaMgGe2O6:Cr3+ phosphor was prepared by a high-temperature solid-state reaction. The phosphor doped with 0.02Cr3+ showed an emission band at 845 nm with a broad bandwidth of 160 nm and a high quantum yield of 84% under 450 nm excitation. The broadband NIR pc-LED was fabricated using CaMgGe2O6:0.02Cr3+ phosphor based on a blue light-emitting diode (LED) chip. A photoelectric efficiency of 27.2% @ 10 mA and an NIR output power of 57.98 mW @ 100 mA were achieved, which are the highest values reported yet for broadband NIR pc-LEDs with a peak wavelength longer than 800 nm. Using the fabricated NIR pc-LED as the light source, the characteristic absorption spectra of some substances were obtained. All of the results indicated that the CaMgGe2O6:Cr3+ phosphor has considerable potential in near-infrared spectroscopic applications.

Highly Efficient Broad-Band Green-Emitting Cerium(III)-Activated Garnet Phosphor Allows the Fabrication of Blue-Chip-Based Warm-White LED Device with a Superior Color Rendering Index.

High-performance warm-white light-emitting diode (LED) devices are in great demand toward green and comfortable solid-state lighting. Herein, we report a creative green-emission CaY2HfGa(AlO4)3:Ce3+ phosphor. CaY2HfGa(AlO4)3:Ce3+ compounds with different cerium ion doping contents have been successfully prepared through a conventional high-temperature solid-state method, and their phase and crystal structure have been revealed via the powder X-ray diffraction and Rietveld refinement. Impressively, the CaY2HfGa(AlO4)3:Ce3+ phosphors exhibit a broad-band excitation, which well covers the wavelength region from the 300 to 500 nm, corresponding to the commercial blue-emitting LED chip. Upon 450 nm excitation, the optimal CaY2HfGa(AlO4)3:2%Ce3+ sample shows an intense broad-band green emission (the corresponding testing spectral range: 460-750 nm) with a strongest peak about 534 nm. In addition, the CaY2HfGa(AlO4)3:2%Ce3+ sample possesses a broad full width at half-maximum equal to 120 nm; moreover, its CIE chromaticity coordinate and the internal quantum efficiency are determined to be (0.3541, 0.5427) and 72.8%, respectively. A high-quality warm-white LED has been fabricated through incorporating our CaY2HfGa(AlO4)3:2%Ce3+ green phosphors and commercial red phosphors with the 450 nm blue LED chip. When upon the 20 mA bias driving current, the LED device demonstrates a bright warm-white light emission, which possesses a satisfactory color rendering index of 91, a low correlated color temperature of 4080 K, as well as a good luminous efficacy of 85.14 lm W-1. The creative green-emitting CaY2HfGa(AlO4)3:Ce3+ garnet phosphor has a bright application prospect toward high-quality warm-white LED lighting.

A novel blue-light excitable Pr3+ doped (Sr,Ba)LaMgTaO6 phosphor for plant growth lighting

In this work, a series of Pr3+ ions doped (Sr,Ba)LaMgTaO6 phosphors were prepared and applied for plant growth lighting. Under 450 nm excitation, (Sr,Ba)LaMgTaO6:Pr3+ exhibits intense reddish emission at around 650 nm which is assigned to the 3P0→3F2 transition of Pr3+ ions. The luminescence intensity reaches to the maximum at 2.5 mol% Pr3+ doping content both in SrLaMgTaO6:Pr3+ and BaLaMgTaO6:Pr3+ systems. Meanwhile, the internal quantum efficiency (IQE) test shows that the IQE of the SrLaMgTaO6:0.025Pr3+ phosphor is 33.34% upon blue light excitation. The decay curves and temperature-dependent luminescence measurements of the (Sr,Ba)LaMgTaO6:Pr3+ phosphors were performed and investigated in detail. The red light emitting diodes (LEDs) were packaged using the SrLaMgTaO6:Pr3+ and BaLaMgTaO6:Pr3+ phosphors combined with a blue LED chip, which are well-overlapped with the absorption band of photosynthesis. Results indicate that the (Sr,Ba)LaMgTaO6:Pr3+ can serve as a component of the red light in plant-growth LEDs.

A strong zero phonon line of Mn4+ in a red-emitting phosphor BaGaF5:Mn4+

In this paper, a single-phase red-emitting phosphor BaGaF5:Mn4+ (BGFM) was synthesized by a hydrothermal method, and its crystal structure and luminescence properties were studied in detail. The results show that the excitation spectra of BGFM samples are mainly composed of two bands located at the near-ultraviolet and blue light region, respectively, while the emission spectra show multiple peaks in the red region. Due to the defects generated with the non-equivalent occupation of Ga3+ by Mn4+, the adjacent [MnF6] octahedron is highly distorted, resulting in a strong zero-phonon line (ZPL, 627 nm) in the emission spectrum. Additionally, the materials have shown a high internal quantum efficiency (QE = 63.7%) and good color stability. Finally, a white LED was obtained by mixing BGFM and commercial Y3Al5O12:Ce3+ yellow phosphor on a blue light-emitting diode (LED) chip.

A near-infrared phosphor doped with Cr3+ towards zero-thermal-quenching for high-power LEDs

Cr3+-doped phosphors show significant application potential in near-infrared (NIR) light-emitting diodes (LEDs). However, the development of thermally stable and efficient NIR phosphors still faces enormous challenges. Herein, NIR phosphors K2NaMF6:Cr3+ (M3+ = Al3+, Ga3+, and In3+) were synthesized by the hydrothermal method. The represented K2NaAlF6:Cr3+ phosphor can be effectively excited by blue light (∼430 nm) to present broadband emission at half a maximum of 96 nm peaking at ∼ 728 nm. Meanwhile, the K2NaAlF6:Cr3+ phosphor exhibits excellent internal quantum efficiency (IQE = 68.08%) and nearly zero-thermal-quenching behavior, which is able to maintain 96.5% emission intensity at 150 °C of the initial value at 25 °C. The NIR phosphor-converted LED was fabricated based on K2NaAlF6:Cr3+ phosphor and a blue LED chip, showing a NIR output power of 394.39 mW at 300 mA with a high photoelectric conversion efficiency of 10.9% at 20 mA. Using the high-power NIR LED as a lighting source, transparent and quick veins imaging as well as non-destructive testing were demonstrated, suggesting the NIR phosphor has a wide range of practical applications.