Efficient Phosphor Research Articles

Large‐Scale Room‐Temperature Synthesis of the First Sb3+‐Doped Organic Ge(IV)‐Based Metal Halides with Efficient Yellow Emission for Solid‐State Lighting and Latent Fingerprint Detection

Organic–inorganic hybrid Ge(II)‐based metal halides have garnered significant interest due to their intriguing photophysical properties and environmentally friendly characteristics. However, challenges such as poor stability, low emission intensity, and a complex synthesis process have hindered their widespread application. In addressing these issues, a breakthrough in the large‐scale production of Sb3+‐doped Ge(IV)‐based metal halide (C13H14N3)2GeCl6 phosphors at room temperature through a straightforward solution method is presented. The synthesized compound exhibits a remarkable bright broad yellow emission band at 590 nm, boasting a photoluminescence quantum efficiency of 99.53 ± 0.06% the highest among Ge(IV)‐based metal halides. Notably, the introduction of Sb3+ induces the formation of Jahn–Teller‐like self‐trapped excitons in [SbCl6]3− species, attributable to lattice distortion and strong electron–phonon coupling. Consequently, Sb3+‐doped (C13H14N3)2GeCl6 demonstrates a large Stokes shift (221 nm) and a prolonged decay lifetime (3.06 μs). Furthermore, the Sb3+‐doped compound exhibits commendable chemical‐ and photostability, prompting exploration in applications such as white light‐emitting diodes and latent fingerprint detection. This work not only provides a practical approach for designing economically viable, environmentally friendly, and highly efficient emission phosphors but also paves the way for novel directions in their expanded application.

Synthesis and photoluminescence properties of high color purity red emitting Li2MgTi3O8:Eu3+ phosphors for warm W-LEDs

In search of efficient and suitable phosphors for white light emitting diodes (w -LEDs), herein, we report Li2MgTi3O8:Eu3+ as red phosphors that are low-cost eco-materials synthesized by solid-state reaction method. XRD patterns confirm the crystallinity and phase purity of the as-prepared phosphors with the successful incorporation of Eu3+ ions. FTIR, FE-SEM and TEM were used to understand the functional groups and morphology of prepared samples respectively. The band gap energy calculated from DRS showed Burstein–Moss effect. Under 398 nm excitation, intense red emission was recorded at 615 nm and lifetime values were in microsecond range. The prepared phosphor possesses quantum efficiency of 31.74%, good thermal stability with an activation energy of 0.254 eV and exhibit warm red emission with 100% color purity. Therefore, the obtained results suggests that the prepared Li2MgTi3O8:Eu3+ phosphors can be considered as an appropriate candidate for the red component in w- LEDs.

Blue-emitting Bi3+-doped K2MGeO5 (M = Hf, Zr) phosphors for full-spectrum WLED: Crystal structure, electronic structure and luminescent properties

Developing efficient and stable blue-emitting phosphors has always been crucial for advancing full-spectrum WLED technology. In this study, the germanates K2MGeO5 (M = Zr, Hf) were chosen as the host to develop novel NUV-excited blue-emitting phosphors. The crystal structure, electronic structure, and luminescence properties of K2MGeO5:Bi3+ were comprehensively investigated using X-ray powder diffraction, Rietveld refinement, photoluminescent spectra analysis, and density functional theory calculations. By integrating experimental data with semi-empirical formula calculations, the excitation and emission sources were elucidated. Furthermore, the influence of Bi3+'s local coordination environment on its luminescence performance and the concentration quenching mechanism in K2MGeO5:Bi3+ were thoroughly examined. A full-spectrum WLED was fabricated by synergistically combining K2ZrGeO5:Bi3+, commercially available green and red phosphors with a 365 nm LED chip. It is anticipated that this study could provide insights for the advancement of blue phosphors excited by near-ultraviolet light.

Iridium(III) Carbene Phosphors with Fast Radiative Transitions for Blue Organic Light Emitting Diodes and Hyperphosphorescence

AbstractIt is envisioned that the efficient and stable blue OLED phosphors can be synthesized using Ir(III) complexes with electron‐deficient carbene cyclometalates. Therefore, three facially coordinated Ir(III) phosphors f‐ct7a‐ c bearing isomeric purinylidene chelates are obtained. They possess three, two, and one 4‐t‐butylphenyl cyclometalate together with the same number of N‐phenyl appendage on carbene fragments, and exhibit photoluminescence centered (λmax) at 452‒461 nm, fast radiative rate constants (kr) of 7.5–11.3 × 105 s‒1, and high quantum yield (PLQY) up to 80% in degassed toluene at RT. Representative OLED based on f‐ct7c gives maximum external quantum efficiency (EQEmax) of 26.6%, CIE(x,y) of 0.16, 0.15, and low roll‐off with EQE of 22.3% at 1000 cd m‒2. Furthermore, they can be utilized to sensitize a deep blue multiple resonance thermally activated delay fluorescence emitter (MR‐TADF), i.e., t‐DABNA. The corresponding hyper‐OLED device based on alternative f‐ct7b realizes an EQEmax of 36.1%, CIE(x,y) of 0.14, 0.09, and full width at half maximum (FWHM) of 26.5 nm. To the understanding, this is the first report on concurrent achieving both the high EQE and small CIEy value for Ir(III)‐based phosphors.

Highly efficient and thermostable far-red phosphor for promoting root growth in plants

Structural modification and spectral optimization of luminescence characteristics of far-red phosphors for plant growth.

An efficient blue-violet phosphor: an advanced material designed for high-quality full-spectrum lighting.

A highly efficient phosphor with exceptional luminescence properties is crucial for achieving high-quality solid-state white-light illumination. Here, this paper presents a groundbreaking discovery, an innovative blue-violet emitting Ba1.31Sr3.69(BO3)3Cl:Ce3+ (BSBCl:Ce3+) phosphor designed with remarkable thermal stability and quantum efficiency for full spectrum white light-emitting diodes (WLEDs). By employing a high-temperature solid-phase method, we synthesized various BSBCl:xCe3+ phosphors with different Ce3+ doping concentrations. Remarkably, BSBCl:0.03Ce3+ displays a broad excitation band from 250 nm to 400 nm, rendering it compatible with commercial near-ultraviolet (UV) LED chips. Under 330 nm excitation, this phosphor emits blue light with an astonishing 88.2% internal quantum efficiency (IQE) and an impressive 60.9% external quantum efficiency (EQE). Notably, when employed in the temperature range of 298-473 K, the synthesized BSBCl:0.03Ce3+ phosphor exhibits exceptional color stability and thermal stability (I423 K/I298 K = 83%). Utilizing BSBCl:0.03Ce3+ as the blue-violet emitting component in the fabrication of WLED devices has demonstrated significant advancements in the color rendering index. These findings underscore the potential of BSBCl:Ce3+ phosphors for a wide range of applications in health-oriented indoor illumination.

Structural Confinement Helps Achieve More Accurate Energy Transfer: Studies on the Garnet Structural NYGIG:Tb3+,Eu3+ Phosphors

In the quest to enhance the performance of white light-emitting diodes (WLEDs), the development of efficient red phosphors is essential. To address these, a series of co-doped garnet-type phosphors, NaY2Ga2InGe2O12:Tb3+,...

Thermal stability and quantum efficiency improvement of Cr3+-activated garnet phosphors via regulating A/B sites for near-infrared LED applications.

The discovery of phosphors with highly efficient broadband near-infrared emission is urgent for constructing NIR sources for various applications. Herein, we synthesized a series of near-infrared emitting garnet-type (A3B2C3O12) Lu2-xCaAl3.99Cr0.01SiO12:xGd/La and Lu2CaAl3.99-yCr0.01SiO12:ySc/Ga phosphors and systematically investigated the effect of A/B-site substitution on the crystal structure and luminescence properties. Structural and optical analyses revealed that the A/B-site substitution weakened the crystal field strength, further enhancing the broadband emission of the allowed 4T2 → 4A2transition and diminishing the narrow-peak emission of the forbidden 2E → 4A2 transition. As expected, NIR phosphors, exemplified by Lu1.7CaAl3.99Cr0.01SiO12:0.3Gd and Lu2CaAl3.49Cr0.01SiO12:0.5Sc, showed outstanding thermal stabilities at 423 K (150 °C) registering values of 103.02% and 94.91%, with high quantum efficiencies of 80.48% and 85.01%, respectively. In addition, pc-LEDs with broadband NIR output and good optoelectronic properties have been realized, demonstrating the great potential of broadband NIR pc-LEDs for applications. This work not only provides a series of high-efficiency phosphors for NIR pc-LED applications, but also provides a systematic idea and an efficient method to improve the luminescence performance of garnet-type phosphors.

CaY2ZrScAl3O12:Cr3+—An efficient and thermally stable garnet phosphor for high-performance NIR LEDs

High-quantum efficiency (QE) and superior luminescence thermal stability NIR phosphors are indispensable for producing advanced NIR pc-LEDs. Despite this, the broadband NIR phosphor peaking around ~780 nm often falls short...

Luminescence center modulation for the synthesis of a narrow-band green phosphor: mechanism and backlighting display application.

A highly efficient and stable green phosphor with a narrow emission-band in a hexagonal aluminate was synthesized based on the energy transfer between Eu2+ and Mn2+ luminescence centers. The related mechanism was elucidated from the viewpoints of the crystal structure and energy level, providing insights for designing novel phosphors with high performance.

Stable and efficient rare-earth free phosphors based on an Mg(II) metal-organic framework for hybrid light-emitting diodes.

Stable and efficient green hybrid light-emitting diodes (HLEDs) were fabricated from a highly emissive Mg(II)-tetraphenyl ethylene derivative metal-organic framework embedded in a polystyrene matrix (Mg-TBC MOF@PS). The photoluminescence quantum yield (ϕ) of the material, >80%, remains constant upon polymer embedment. The resulting HLEDs featured high luminous efficiencies of >50 lm W-1 and long lifetimes of >380 h, making them among the most stable MOF-based HLEDs. The significance of this work relies on the combination of many features, such as the abundance of the metal ion, the straightforward scalability of the synthetic protocol, the great ϕ reached upon phosphor fabrication, and the state-of-the-art HLED performances.

An efficient and thermally stable source with Cr3+ near-infrared luminescence for non-destructive testing applications

The quest for efficient and heat-resistant near-infrared (NIR) phosphors to create advanced smart NIR lighting sources continues to pose a significant challenge. This study introduces a new fluoride phosphor, Cr3+-doped Cs2NaScF6, wherein the Cs2NaScF6 host provides a weak crystal field suitable for Cr3+ doping. This arrangement allows the production of a broad NIR emission peaking at 797 nm, coupled with a notable internal quantum efficiency of 90.8 % when excited by 446 nm blue light. Meanwhile, due to the relatively mild electron-phonon coupling effect and a high activation energy within this phosphor, the overall NIR emission intensity at 150 °C sustains 81.8 % of its level at room temperature. This highlights exceptional thermal stability in photoluminescence performance. Combining the Cs2NaScF6:Cr3+ phosphor with a commercially available blue InGaN chip to construct a NIR light-emitting diode (LED) device, which exhibits efficient and stable NIR emission, making it suitable for non-destructive testing applications. These findings affirm that the Cs2NaScF6:Cr3+ phosphor can function as a promising candidate to fabricate high-performance device for NIR spectroscopy application.

Exploring the potential of lanthanide-doped oxyfluoride materials for bright green upconversion and their promising applications towards temperature sensing and drug delivery.

The most efficient upconversion (UC) materials reported to date are based on fluoride hosts with low phonon energies, which reduce the amount of nonradiative transitions. In particular, NaYF4 doped with Yb3+ and Er3+ at appropriate ratios is known as one of the most efficient UC phosphors. However, its low thermal stability limits its use for certain applications. On the other hand, oxide hosts exhibit better thermal stability, yet they have higher phonon energies and are thus prone to lower UC efficiencies. As a result, developing host nanomaterials that combine the robustness of oxides with the high upconversion efficiencies of fluorides remains an intriguing prospect. Herein, we demonstrate the formation of ytrrium doped oxyfluoride (YOF:Yb3+,Er3+) particles, which are prepared by growing a NaYF4:Yb3+,Er3+ layer around SiO2 spherical particles and consecutively applying a high-temperature annealing step followed by the removal of SiO2 template. Our interest lies in employing these materials as Boltzmann type physiological range luminescence thermometers, but their weak green emission is a drawback. To overcome this issue, and engineer materials suitable for Boltzmann type thermometry, we have studied the effect of introducing different metal ion co-dopants (Gd3+, Li+ or Mn2+) into the YOF:Yb3+,Er3+ particles, focusing on the overall emission intensity, as well as the green to red ratio, upon 975 nm laser excitation. These materials are explored for their use as ratiometric thermometers, and further also as drug carriers, including their simultaneous use for these two applications. The investigation also includes examining their level of toxicity towards specific human cells - normal human dermal fibroblasts (NHDFs) - to evaluate their potential use for biological applications.

Electronic structure, colour-tunable emission and energy transfer in Li3Ba2Y3(WO4)8:Bi3+,Eu3+ phosphors for white light-emitting diodes.

Solid-state phosphor-converted white light-emitting diodes (pc-WLEDs) are the leading trend of the lighting industry in the 21st century. To pursue high quality WLED lighting, the development of highly efficient phosphors with tunable luminescence has become a hot research topic. Herein, we reported for the first time on Bi3+/Eu3+-doped Li3Ba2Y3(WO4)8 phosphors that exhibited tunable emission and high energy transfer efficiency of 89.90% from Bi3+ to Eu3+. The phase purity, microstructure, electronic structure and photoluminescence properties of these phosphors were studied in detail. Bi3+ and Eu3+ were effectively doped in Li3Ba2Y3(WO4)8 with an optical bandgap of 3.81 eV. The band structure and density of states were quantitatively evaluated by density functional theory simulation. At an excitation wavelength of 342 nm, the Bi3+-doped phosphor achieved yellow-green emission. By alloying Eu3+ into Li3Ba2Y3(WO4)8:Bi3+, the luminescence gradually turned red due to the energy transfer from Bi3+ to Eu3+. Moreover, the activation energy of the prepared phosphor was 0.1897 eV, demonstrating excellent thermal stability. Eventually, by combining Li3Ba2Y3(WO4)8:4%Bi3+,4%Eu3+ and a blue-emitting BAM:Eu2+ phosphor with a 365 nm ultraviolet chip, a WLED device with a high colour rendering index (Ra) of 78.7, chromaticity coordinates of (0.3401, 0.3131) and correlated colour temperature of 5080 K was successfully achieved. This work provided new insights into the design and development of color-tunable phosphors for white LEDs.

Synthesis and luminescent properties of a new cyan Ca18Li6-3xYx(PO4)14:0.1Eu phosphors and PVA-based composite films for multifunctional applications

The development of light-emitting materials capable of efficiently emitting broad-band cyan light is of paramount importance in the quest for full-spectrum white light illumination. In this study, a series of new Ca18Li6-3xYx(PO4)14:0.1Eu phosphors with adjustable luminescent properties were synthesized through a high-temperature solid-phase method, and the investigation encompassed an analysis of their crystal structures, luminescence characteristics, and thermal stability. Meanwhile, the optimal doping concentration of Y3+ ions in the Ca18Li6-3xYx(PO4)14:0.1Eu host was identified to be x = 0.3, achieved through the modulation of the substitution ratio of Y3+ to Ca2+ to regulate the occupancy of Eu2+ at different sites. The resulted in the generation of asymmetric cyan color emission spectra (FWHM = 47 nm) with broad-band emission spanning the 425–550 nm range under 378 nm excitation. In addition, the application of the optimized cyan-emitting phosphor Ca18Li5.1Y0.3(PO4)14:0.1Eu in w-LED devices led to a significant enhancement in the CRI from 89.1 to 91.2, accompanied by a reduction in the correlated color temperature from 4896 K to 4566 K. These results highlight the potential utility of the cyan-emitting Ca18Li5.1Y0.3(PO4)14:0.1Eu phosphors in full-visible-spectrum solid-state illumination. Notably, the optimized cyan-emitting phosphor Ca18Li5.1Y0.3(PO4)14:0.1Eu was synthesized in conjunction with soluble polyvinyl alcohol (PVA) to yield a transparent anti-counterfeiting ink. The resulting film exhibited exceptional flexibility, foldability, and superior thermal and optical properties. Moreover, the emission band of this phosphor, situated in the 425 nm–550 nm spectral region, represents a crucial blue light source beneficial for plant growth. In summary, the highly efficient phosphor Ca18Li5.1Y0.3(PO4)14:0.1Eu is a promising material with multifunctional luminescent potential for general illumination, anti-counterfeiting, and light-converting agricultural films.

Crystal Structure–Photoluminescence Correlations in Ce3+-Doped Ca2ZnSi2O7phosphors

In this work, Ce3+-doped Ca2-x ZnSi2O7:xCe3+ phosphors were prepared by the solid-state reaction in air. The crystal structure and photoluminescence properties of the prepared phosphors were investigated. All the prepared samples formed the tetragonal crystal structure. XRD Rietveld refinement was performed to retrieve a detailed crystal structure of the Ca2-x ZnSi2O7:xCe3+ phosphors. The lattice parameters a and c increased with increasing Ce3+concentration. The lattice parameters a and c of the Ca1.996ZnSi2O7: 0.004Ce3+ phosphor were 7.825 Å and 5.015 Å, respectively. The Ca2-x ZnSi2O7:xCe3+ phosphors showed strong and asymmetric bands covering the 415 to 650 nm range, which were attributed to the transitions of Ce3+ ions from the 5d excited state to the 2F5/2 and 2F7/2 ground states. The emission intensity increased with increasing Ce3+concentration up to x = 0.012. The dipole-dipole interaction was responsible for the concentration quenching. The CIE coordinate (x, y) was located in the blue spectral region. These results indicate that the prepared Ca2-x ZnSi2O7:xCe3+ phosphors can serve as an efficient blue phosphor in the white light emitting diodes.

Spectroscopic properties and thermal stability of a Mn4+-doped polyfluoride phosphor for application in solid-state lighting

In this study, an efficient polyfluoride red-emitting phosphor, Cs3RbGe2F12:Mn4+ (denoted as CRGF:Mn), has been synthesized using a simple co-precipitation method. The crystal and electronic structures, spectroscopic properties, and photoluminescence thermal stability of CRGF:Mn have been systematically characterized. The results show that Mn4+ ions experience a strong crystal field and present a series of intense red emission peaks under blue light excitation. Moreover, CRGF:Mn exhibits a high color purity (95.1 %), high internal quantum efficiency (82.4 %), and enhanced photoluminescence thermal stability at 150 °C, with an intensity of 113 % relative to room temperature. A warm white light-emitting diode exhibiting a low correlated color temperature (3572 K), high color rendering index (90.7), and suitable luminous efficiency (132.6 lm/W) was prepared using CRGF:Mn as a red component, demonstrating viable application in solid-state lighting.

Highly Efficient Three‐Photon Excited Red Emission in the Yb3+‐Er3+ Upconversion System at Low Excitation Intensities for Non‐Invasive Anti‐Counterfeiting

AbstractUpconversion (UC) phosphors exhibiting luminescence color tuning (LCT) through variations in infrared excitation intensity offer great potential for high‐security anti‐counterfeiting applications. However, the current LCT capability is limited to high excitation intensities, hindering developments of non‐invasive counterfeit detection. In this study, two orders of magnitude reduction are achieved in excitation intensities for LCT in YF3:Yb/Er, accomplished by attaining an unprecedentedly efficient three‐photon excited red emission for mixing with the two‐photon excited green emission. To enable this breakthrough, deoxygenation techniques are employed during sample preparations, which surprisingly prevent concentration quenching of Yb3+ ions, facilitating efficient three‐photon excitation of the red emission for Yb3+ concentrations ≥ 30% even at excitation intensities as low as 10 mW cm−2. At excitation intensities of 100 mW cm−2, the three‐photon excitation contributes to 91–94% of the red emission, resulting in an 11–17‐fold increase in the red‐to‐green intensity ratio. This low‐excitation‐induced LCT, shifting from green to orange, showcases its potential for anti‐counterfeiting. Furthermore, present YF3:Yb/Er phosphors demonstrate an impressive UC quantum yield of 7.8%, surpassing the popular NaYF4:Yb/Er phosphor (5.6%) under the same excitation intensity of 31.8 W cm−2. These findings represent a significant advancement in highly efficient UC fluoride phosphors, promising diverse applications across various fields.

High Output Power and High Quantum Efficiency in Novel NIR Phosphor MgAlGa0.7 B0.3 O4 :Cr3+ with Profound FWHM Variation.

There is strong demand for ultraefficient near-infrared (NIR) phosphors with adjustable emission properties for next-generation intelligent NIR light sources. Designing phosphors with large full-width at half-maximum (FWHM) variations is challenging. In this study, novel near-ultraviolet light-emitting diode(LED)-excited NIR phosphors, MgAlGa0.7 B0.3 O4 :Cr3+ (MAGBO:Cr3+ ), with three emission centers achieve ultra-narrowband (FWHM = 29nm) to ultra-broadband (FWHM = 260nm) emission with increasing Cr3+ concentration. Gaussian fitting and decay time analysis reveal the alteration in the FWHM, which is attributed to the energy transfer occurring between the three emission centers. The distinct thermal quenching behaviors of the three emission centers are revealed through the temperature-dependent decay times. The ultra-broadband NIR phosphor MAGBO:0.05Cr3+ exhibits high thermal stability (85%, 425 K) and exceptional external quantum efficiency of 68.5%. An NIR phosphor-converted LED (pc-LED) is fabricated using MAGBO:0.05Cr3+ phosphor, exhibiting a remarkable NIR output power of 136mW at 600mA in ultra-broadband NIR pc-LEDs. This study describes the preparation of highly efficient phosphors and provides a further understanding of the tunable FWHM, which is vital for high-performance NIR phosphors with versatile applications.

Full-visible-spectrum LED lighting by using a near-UV-excitable broadband blue-emitting Ca2LuHf2GaAl2O12:Ce3+ garnet phosphor

Highly efficient broadband blue-emitting phosphors are urgently needed for full-visible-spectrum white light-emitting diodes (WLEDs). Herein, we report a new highly luminescent garnet-type Ca2LuHf2GaAl2O12:Ce3+ (abbreviated as: CLHGAO:Ce3+) blue phosphor enabling full-visible-spectrum LED lighting. These CLHGAO:Ce3+ phosphors doped with different Ce3+ concentrations have been prepared by using a high-temperature solid-state reaction approach, and their phase purity, crystal structure, luminescent properties, CIE color coordinates, and quantum efficiency have been systematically studied. Importantly, CLHGAO:Ce3+ blue phosphors show a broadband excitation spectrum in the 300–450 nm spectral range peaking around 398 nm, matching well with the emission wavelengths of commercial near-ultraviolet LED chips (380–420 nm). Upon 398 nm excitation, the optimal CLHGAO:2%Ce3+ phosphor sample generates a bright broad blue emission band (emission peak: 472 nm; bandwidth: 84 nm) with high internal quantum efficiency of 79.2% and external quantum efficiency of 55.3%. Notably, the emission intensity of CLHGAO:2%Ce3+ phosphor is about 1.87 times higher compared to the commercial BaMgAl10O17:Eu2+ blue phosphor (emission peak: 451 nm; bandwidth: 53 nm). Finally, a white LED device is fabricated with a 395 nm near-UV LED chip with CLHGAO:2%Ce3+ blue phosphor and commercial (Ba,Sr)2SiO4:Eu2+ green phosphor as well as commercial CaAlSiN3:Eu2+ red phosphor, and the device demonstrates bright warm-white emission with an ultrahigh color rendering index (Ra = 95.1, R9 = 97.8, R12 = 88.4) and low correlated color temperature of 3540 K. These results show that as-developed blue-emitting CLHGAO:Ce3+ garnet phosphors with superior photoluminescence properties can potentially be used in phosphor-converted full-visible-spectrum WLEDs.