A series of Pr3+-doped Sr2NaMg2V3O12 (SNMV) garnet phosphors were successfully synthesized by a high temperature solid-state method. The crystal structure, luminescence properties and temperature sensing properties of the phosphors were systematically studied. Under excitation at 339 nm, SNMV:Pr3+ phosphors exhibit strong blue-green broadband emission in the wavelength range of 400-700 nm and typical red emissions of Pr3+ at 612 nm and 624 nm, which correspond to the energy level transition of the [VO4]3- group and the 1D2 → 3H4,5 transition of Pr3+, respectively. Furthermore, in the temperature range of 98-298 K, high sensitivity optical temperature sensing is realized based on the fluorescence intensity ratio (FIR) and the fluorescence lifetime (FL). In FIR mode, the maximum absolute sensitivity (Sa) and relative sensitivity (Sr) of the phosphor are 0.01782 K-1 (298 K) and 1.13543% K-1 (298 K), respectively. In FL mode, the maximum Sa and Sr values are 0.0889 K-1 (198 K) and 0.62752% K-1 (223 K), respectively. The results show that SNMV:Pr3+ phosphors have great potential in the field of optical temperature measurement.

In this work, a GdMgAl(11)O19: Dy3+ phosphor with dual functions of optical temperature sensing and white light illumination was synthesized using the high-temperature solid-state method. When excited by 348 nm UV light, the phosphor emits warm white light, and its luminescence behavior exhibits both overall thermal stability and local thermal sensitivity. By utilizing the reverse response characteristics of the luminescence intensity of two blue emission bands corresponding to Dy3+ thermally coupled level transitions (F-4(9/2) -> H-6(15/2), 452 nm; I-4(15/2) -> H-6(15/2), 476 nm) with temperature, its optical temperature sensing potential was explored using the fluorescence intensity ratio (FIR) method. Experimental results show that this phosphor can perform temperature detection over a wide range of 298-973 K, with a relative sensitivity of 0.746% K-1 at 298 K. Among all emission peaks, the 452 nm emission peak is a locally thermally sensitive peak, accounting for a very small proportion of the overall emission and having no decisive effect on the overall luminescence. The fluorescence intensities of the 476 nm blue, 570 nm yellow, and 663 nm red emissions, however, show consistent attenuation with increasing temperature. Even when the temperature rises to 423 K, the fluorescence intensity still retains 85% of its initial room temperature value, indicating excellent overall thermal stability. GdMgAl11O19:Dy3+ phosphor integrates the dual functions of high-stability white LED and wide-range high-sensitivity optical temperature sensing. This study provides important reference for the application expansion of Dy3+-doped phosphors in LED devices and temperature detection systems, as well as for the development of multifunctional phosphors.

The advancement of next-generation near-infrared phosphor-converted LEDs (NIR pc-LEDs) relies critically on the development of high-performance NIR phosphors. However, the NIR phosphors is often limited by low external quantum efficiency (EQE) and significant thermal quenching. Herein, we report a series of high-power tunable NIR phosphors achieved through a combined strategy of [M2+-Si4+] (M = Mg2+, Ca2+, Sr2+) co-substitution and flux-assisted synthesis. The resulting Cr3+-doped garnet-type MxLu3-xGa5-xSixO12 phosphors demonstrate both high quantum efficiency and outstanding thermal stability. Notably, the phosphor achieves an EQE of 53.9% and retains over 104.5% of its room-temperature luminescence intensity at 423 K, enabling an LED output power of 74.5 mW at 200 mA and a high photoelectric conversion efficiency of 16.6%@10 mA. These advances stem from crystal field regulation, Cr3+-Cr3+ pairs formation, and co-substitution induced lattice distortion, which collectively broaden the emission spectrum and boost luminescence intensity. Moreover, the flux-assisted synthesis improves crystallinity and homogenizes ion diffusion by lowering the viscosity of the molten phase, thereby boosting thermal quenching resistance and overall device efficiency. This work utilizes a dual-optimization strategy for both microscopic and macroscopic properties and develops a high-performance NIR phosphor system, providing key insights for future NIR pc-LEDs.

In this work, a series of near-infrared persistent luminescent phosphors CaSnO3:Bi,xMg2+ were prepared via Mg2+ co-doping, and the effects of Mg²⁺ doping on the structure, luminescence properties, Bi valence state, and defects of the phosphors were systematically studied. The results show that at low doping concentrations, Mg²⁺ primarily enters the CaSnO3 lattice in an interstitial manner, leading to lattice expansion. The interstitial incorporation of Mg²⁺ introduces positive charges, which promotes the reduction of Bi³⁺ to Bi²⁺, thereby increasing the concentration of Bi²⁺ and enhancing the near-infrared photoluminescence efficiency of the phosphors. Moreover, Mg²⁺ codoping modified the defect distribution in the phosphor, which further enhances the near-infrared persistent luminescence intensity. Under the optimal Mg2+ doping concentration, the photoluminescence intensity of the phosphor increased by 0.8 times, and the initial persistent luminescence brightness improved by 6.3 times compared to the Bi singly-doped sample. This study not only provides a new near-infrared persistent luminescent phosphor but also offers a novel strategy for regulating the valence state of Bi ions through interstitial codoping to prepare Bi2+-based near-infrared persistent phosphors.

In this study, a series of non-gallate broadband near-infrared Mg1.4Zn0.6SnO4:Cr3+,Bi3+ phosphors were successfully synthesized via solid-state reaction method. Occupying octahedral sites in a weak crystal field environment, Cr3+ ions in Mg1.4Zn0.6SnO4 exhibit intense broadband near-infrared emission centered at 759 nm, which originates from two distinct Cr3+ centers located at Sn4+ and Mg2+/Zn2+ sites. Although Bi3+ does not contribute to luminescence in this phosphor and its co-doping has minimal influence on the crystal structure, Cr3+ valence, or the concentration of effective traps, it significantly enhances both the luminescence efficiency and persistent luminescence performance by improving the crystallinity of the phosphor. With Bi3+ codoping the external quantum efficiency of the phosphor was promoted from 15 % to 21 % and the persistent-luminescence duration was extended to over 48 h. Furthermore, the potential application of Mg1.4Zn0.6SnO4:0.01Cr3+,0.07Bi3+ in NIR phosphor-converted LED is explored and demonstrated. This work not only provide a new non-gallate broadband near-infrared phosphor but also proposes a new strategy for synchronously improving the luminescence efficiency and persistent-luminescence performance of Cr3+ activated phosphors for multifunctional applications.

Traditional commercial white light-emitting diodes (WLEDs) suffer from insufficient cyan light intensity and substandard spectral continuity, which restricts their application in the field of high-end lighting. To improve the performance of WLEDs, there is an urgent need for suitable and bright cyan phosphors. Herein, we report a bright cyan-emitting phosphor BaAlSi5N7O2:Ce3+, which exhibits a broadband centered at 479 nm with a full-width at half-maximum (FWHM) of 99 nm. The phosphor also exhibits exceptional thermal stability, retaining 94% of its room-temperature luminescence intensity at 150 degrees C. When integrated into full-spectrum phosphor-converted WLEDs, BaAlSi5N7O2:Ce3+ effectively compensates for cyan light deficiency in blue/yellow/red phosphor systems and enhances the color rendering index (Ra) of RGB (red/green/blue)-based WLEDs. Furthermore, BaAlSi5N7O2:Ce3+ serves as an independent high-efficiency cyan component, replacing conventional blue modules to reduce harmful high-energy blue light exposure. In full-spectrum WLEDs fabricated by combining this phosphor with commercial red/green phosphors on near-ultraviolet (n-UV) LED chips, the device achieves Ra = 94.2, correlated color temperature (CCT) = 4044 K, and minimal high-energy blue light (similar to 5%). It demonstrates stable chromaticity coordinates and high luminous efficiency under 10-120 mA current, providing a high-performance cyan phosphor solution for healthy lighting.

In this study, Tm3+-doped Ca2MgWO6 (CMWO) phosphors were prepared and thoroughly analyzed. The structure, luminescent and temperature-dependent behavior of the phosphors were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), photoluminescence (PL) and excitation (PLE) spectra, along with temperature-dependent PL spectroscopy. XRD and SEM analysis confirmed the successful preparation of a pure-phase double perovskite structured Ca2MgWO6 phosphor with successful Tm3+ doping. The PL spectrum indicates that the phosphor emits light under both 285 nm and 361 nm excitation. The PLE spectrum reveals that the optimal doping concentration of Tm3+ for 285 nm excitation is 0.007, while for 361 nm excitation, it is 0.08. The phosphor was then tested for variable-temperature emission spectra, and its temperature-sensing performance was evaluated using the fluorescence intensity ratio (FIR) method. Under 361 nm excitation, the CMWO:0.08 Tm3+ phosphor exhibited a maximum relative sensitivity (S-r(max)) of 2.33 % K-1 at 348 K, within the temperature range of 198-348 K. When excited at 285 nm, the CMWO:0.007 Tm3+ phosphor displayed strong temperature dependence in the range of 98-223 K, with an S-r(max) of 14.71 % K-1 at 223 K, surpassing many thermometric phosphors reported in the literature. These results highlight the significant potential of CMWO:Tm3+ phosphors as highly sensitive optical temperature sensors, particularly for low-temperature applications.

With the development and application of cryogenic technology, the demand for temperature measurement in cryogenic environment is increasing. Optical sensing can provide a non-contact method of temperature measurement in cryogenic environments. Herein, a new temperature measurement route based on the persistent luminescence is proposed. The single-component, coordination crystal Zn-ddcphpy with electron donor and acceptor structures, achieving persistent luminescence (6-7 s) after irradiating by ultraviolet light source at 80 K. The persistent luminescence decay and electron paramagnetic resonance show that the reason for the persistent luminescence generation is the photogenerated charge separation and recombination. In cryogenic environment controlled by liquid nitrogen (80-260 K), the persistent luminescence duration decreases with increasing temperature, the color gradually changes from green to yellow with the spectrum red-shift. Taking Zn-ddcphpy as a model material, the unquiet temperature sensitive based persistent luminescence shows convenience, intuitive and inexpensive. Furthermore, the LPL (long-persistent luminescence) of Zn-ddcphpy exhibits high sensitivity and responsiveness to temperature at cryonic environment, make it suitable for temperature measurement on real time. In this work, the change of duration and color can indicate temperature without contact, which can be used for temperature measurement and monitoring in the fields of cryogenic wind tunnels, cold chain storage, etc.

Although Bi3+ ions exhibit exceptional luminescent properties and spectral tunability, their potential as activators for near-infrared (NIR) ultrawideband emission remains underexplored, while transition metal ions such as Ni2+, Fe3+, and Cr3+/4+ have long been the predominant candidates in this demanding research area. Herein, we demonstrate ultrawideband emission from 400 to 1700 nm in K2MgGeO4:Bi3+ (KMGO:Bi3+), achieving an internal quantum efficiency (IQE) of 88.02% and external quantum efficiency (EQE) of 66.41%. The emission spectrum features interconnected visible and NIR bands, peaking at 614 and 1125 nm, respectively. Notably, the full width at half-maximum (FWHM) of the NIR band exceeds 340 nm, significantly broader than most of the conventional phosphors doped with transition metal ions. Through a comprehensive combination of experimental investigations and crystal structure analysis, we elucidate the underlying mechanism of this ultra-broadband emission, attributing it to Bi3+ centers formed by the substitution of K+ and Mg2+ sites. This work expands the role of Bi3+ ions as activators in the second NIR (NIR-II) region, offering new insights into the design of ultra-broadband-emitting materials and introducing the only known phosphor capable of spanning the full 400 nm to 1700 nm spectrum, thereby filling a longstanding gap in this field.

Ba2Mg(BO3)(2):RE3+(RE = Dy, Tb or Tm) phosphors are synthesized by high-temperature solid-state reaction method and their thermoluminescence (TL) properties under the beta-ray irradiation were studied. Tm3+ is the most efficient activator in this system and its deconvoluted TL glow curve shows a main TL peak at about 160 degrees C. The peak position of Tm3+-doped Ba2Mg(BO3)(2) phosphor shifts to the high temperature with the increase of beta-ray irradiation dose and its beta-ray dose response was linear in the range from 0.115 to 0.952 Gy. Further, the kinetic parameters of Ba2Mg(BO3)(2):RE3+ were estimated by the peak shape method and the heating rate method, and the calculated average activation energies and the frequency factor were 0.98 eV, 3.31 x 10(10 )s(-1) and 0.94 eV, 1.04 x 10(10) s(-1), respectively, highly consistent with each other.

Near-infrared (NIR) luminescence materials with narrow-band emissions are essential for brain and muscle activity imaging based on the absorption difference of oxygenated proteins. However, most known NIR-emitting materials are limited by low external quantum efficiency (EQE) and broadband properties. This work presents the careful design of Tm, Na-doped strontium sulfide (SrS: Tm3+, Na+) phosphor for NIR light-emitting diode (LED), which shows a narrow emitting band of 27 nm. The successful incorporation of Na+ into SrS: Tm3+contrib- utes to the suppression of lattice phonons, resulting in significant improvement in EQE from 33.6% to 53.7% and an increase in thermal stability. The efficient host absorption and energy transfer are facilitated by the crystallographic Sr defects and the distortion in the symmetric crystal, disclosed by solid-state NMR, electron paramagnetic resonance (EPR), transient spectra, and X-ray total scattering analysis. Subsequently, efficient identification of vascular patterns based on the differential absorption of hemoglobin enables the potential application of rare-earth luminescent materials in NIR phosphor-converted light-emitting diodes (pc-LEDs) and bioimaging.

Near-infrared phosphor conversion light-emitting diode (NIR pc-LED) is a widely used ideal NIR light source due to its unique advantages of low cost, energy saving, compactness and long operational lifetime. However, there is currently a scarcity of appropriate phosphor for NIR light sources utilized in spectral detection, with emission peak larger than 850 nm and steady spectrum output of ultra broadband spectra. Here, a broadband Cr3+ activated LiScSnO4 (LSS) phosphor (lambda ex-max = 460 nm) matching the pump band of commercial blue LED chips has been developed, which shows a long wavelength NIR emission peaking at 900 nm. Cr3+ simultaneously replace the Wyckoff site co-occupied by Sc and Sn in LSS. Due to the difference of local environment of the specific crystal field, two different wide emission bands are caused. These two broad emission bands both contribute to the broadband luminescence with a full width at half maximum (FWHM) of 227 nm. Benefiting from the crystallography consistent Wyckoff position occupation of Cr3+ ions, the spectral distribution of LSS: Cr3+ exhibit excellent stability over a wide temperature span (80-423 K). The broadband NIR pc-LED prototype based on LSS:Cr3+ shows great potential in NIR spectrum detection, night vision imaging applications.

Near-infrared (NIR) persistent luminescence (PersL) phosphors have gained significant study attention in bioimaging and biomedical fields due to the advantages of persistent emission and elimination of biological tissue autofluorescence. However, PersL phosphors generally have difficulty in guaranteeing both good thermal stability and external quantum efficiency (EQE), which limits the multi-functional applications of NIR PersL phosphors. Herein, we developed a novel multifunctional NIR PersL phosphor BaLu2Al2Ga2SiO12:Cr3+ (BLAGSO: Cr3+). Interestingly, this NIR phosphor has good thermal stability (99.7 %@150 degrees C for BLAGSO:0.03Cr3+) and promising EQE (31.08 % for BLAGSO:0.03Cr3+). To further improve its PersL performance, Tb3+ ion which is believed to act as a modulator of matrix defects and enhances the storage capacity of traps for electrons is introduced into BLAGSO:0.03Cr3+ and an optimal PersL duration of more than 48 h is achieved. Meanwhile, BLAGSO:0.03Cr3+, 0.03 Tb3+ also exhibits good photo-stimulated PersL (PSPL) ability, and the quenched PersL can be rejuvenated by external photo-stimulation. The potential uses of BLAGSO:0.03Cr3+, 0.03 Tb3+ in NIR pcLEDs and bioimaging are explored and demonstrated. This work is anticipated to drive the research of multifunctional NIR PersL phosphors.

Traditional anti-counterfeiting luminescent phosphors are usually composed of single-mode photoluminescence materials, which greatly limits the security of encryption by its static fluorescent pattern. Herein, multi-mode luminescence properties are achieved including fluorescence and persistent luminescence (PersL) within single host by co-doping Bi3+ and Eu3+ in CaNaSb2O6F (CNSOF). A tunable emission is observed from blue (Bi3+, P-3(1)-> S-1(0)) to white and then to orange-yellow (Eu3+, D-5(1)-> F-7(2) and D-5(0)-> F-7(0, 1, 2, 3, 4)) as the excitation schemes, environment temperatures and doping level are modulated. Impressively, the blue emission attributed to the Bi3+ rapidly disappears after stopping the excitation light irradiation, and only the intense orange-yellow PersL produced by Eu3+ can be observed. And a possible model for the energy transfer and PersL mechanism is proposed by the investigation crystal structure and photoluminescence/PersL. A schematic of security logo and digital information encryption is demonstrated using the prepared samples, which shows the dynamic evolution of the emission color and PersL brightness. The excellent property of multiple color outputs, different decay processes, and external field stimulation modes (including low energy light, thermal, and mechanical stimuli) present in CNSOF:Bi3+, Eu3+ provides a fast, low-cost, and effective method for advanced anti-counterfeiting and information encryption applications.

The near-infrared (NIR) persistent luminescence (PersL) materials have attracted widespread attention owing to the unique self-sustained light with good penetrability. Currently, most of the reported NIR PersL materials are activated by Cr3+. Considering the potential toxicity of chromium ions, there is an urgent requirement to explore the Cr3+-free NIR phosphors. Herein, a novel NIR phosphor Sr2LuSbO6:Fe3+ (SLSO:Fe3+) is prepared and its luminescence properties are systematically studied. The Fe3+-activated Sr2LuSbO6 exhibits a long-wavelength NIR emission band centered at 890 nm with a 110 nm full-width at half maximum (FWHM), and its PersL can last over 18 h. The phosphor shows excellent PersL stability even after being dispersed in solutions of different environments for 7 days. Furthermore, the PersL emitted by the phosphor can penetrate the 2 cm thickness beef, evidencing its good NIR PersL penetration property. This work provides a novel NIR PersL materials based on Fe3+ luminescence for technological applications and also contributes to accelerate the development of new-generation Fe3+-doped NIR PersL phosphor toward versatile applications.

Manipulating photon absorption and trap energy supply ensures the adjustable luminescence intensity of colored sample, and ultimately achieve dynamic anti-counterfeiting modes dependent on wavelength, time and space.

A pseudo-octahedral coordination structure of Mn4+ has been innovatively designed, which has realized the maximum red shift and the widest full width at half-maximum (FWHM) of Mn4+ emission so far, not only extending the emission wavelength of Mn4+ to the near-infrared (NIR) region, but also effectively broadening its bandwidth. In the Ba3Ca4(BO3)3(SiO4)Cl:Mn4+ (BCBSC:Mn4+) phosphor, the [Mn/Ca1O9] polyhedron contains one [Mn/Ca1O6] octahedron, which constitutes the pseudo-octahedral coordination structure of Mn4+. The BCBSC:Mn4+ phosphor can be excited at 362 nm and 470 nm and exhibits a broadband NIR emission centered at ∼756 nm with a super-wide range from 650 nm to 1100 nm. The FWHM can reach ∼90 nm. In addition, the internal quantum efficiency (IQE) of the BCBSC:0.01Mn4+ phosphor is 69.7%. The unique luminescence characteristics of BCBSC:Mn4+ phosphors are explored using experimental data and first principles calculation. The significant redshift, the abnormal broadband emission, and the high luminous efficiency are closely related to the special highly distorted [Mn/Ca1O6] pseudo-octahedral coordination environment. The results contribute to comprehending the mechanism of the broadband NIR emission of Mn4+ activated phosphors and broaden the research ideas of developing high-performance Mn4+ doped phosphors for NIR phosphor-converted light-emission diode applications.

The distribution of phosphor particles within the phosphor film is a decisive factor in the performance of LED light-emitting devices. This study utilized both experimental and numerical methods to examine the impact of temperature on the distribution of phosphor particles within a phosphor film and its resultant effect on the luminescence performance during the curing process. The research found that natural convection caused by temperature gradients during the curing process leads to an uneven distribution of particles in the horizontal direction. In addition, it was observed that the viscosity of the organic silicone decreases at the beginning of the process due to an increase in temperature, which exacerbates the natural convection phenomenon. However, as the temperature continues to rise, the cross-linking reaction of the organic silicone intensifies, causing the viscosity to increase more rapidly and ultimately inhibiting natural convection. The final distribution of particles within the phosphor film demonstrated a tendency for concentration and particle size to decrease with the center of the bottom of the film spreading out in all directions. Optical simulations were also performed on the obtained particle distribution, which revealed significant differences in peak intensity at 460 nm and around 560 nm, as well as a nonlinear relationship between temperature variation and correlated color temperature (CCT) and luminescence uniformity.