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Red-emitting phosphors play a pivotal role in the field of lighting technologies. This study introduces an innovative class of Li 6 SrEu 2 Sb 2 O 12 garnet-structured phosphors, distinguished by the resistance to concentration quenching. A comprehensive examination of the crystal structure, electronic configuration, and photoluminescence characteristics has been conducted. Notably, the doping Eu3+ ions and their doping concentrations barely affected the crystal structure and morphology, and the band gap slightly decreased as the doping concentration increased. Interestingly, the obtained samples exhibit an ultra-high color purity, good thermal stability (78.60 % at 423 K), and suitable internal photoluminescence quantum yield (44.18 %). Consequently, a phosphor-converted white LED has been successfully fabricated, which boasts an outstanding correlated color temperature of 3271 K. Beyond conventional application, this research also introduces the concept of innovative flexible-transparent displays harnessing the phosphor film. Overall, this work has synthesized a groundbreaking red-emitting phosphor, poised to enhance traditional lighting sources and potentially pave the way for new applications in the field of advanced optical displays. [ABSTRACT FROM AUTHOR]

This study focuses on the facile combustion synthesis of highly luminescent Y2O3:Sm3+, Gd3+ nanophosphors, bringing down the thermal budget to a minimum of 500 K. When Sm3+ ions are doped in the Y2O3 cubic crystal system of bandgap 5.6 eV and studied under a down-conversion excitation of 260 nm, the emission spectra offered an intense vermilion color at 608 nm due to the 4G5/2 → 6H7/2 transition within the Sm3+ ions. The Y2O3:2wt%Sm3+ matrix is co-doped with 3wt%Gd3+, highlighting 100% pure vermilion emission 4.21 times higher than doped samples, which is a perfect choice for domestic lightening owing to better eye compatibility. Further, post-annealing is performed to improve the structural parameters and luminescence properties, creating sufficient alterations in the crystal lattice. It is professed that Y2O3:Sm3+, Gd3+ nanophosphors can be effectively used in optoelectronic devices, owing to their enhanced crystallinity and photoluminescence properties resulting from the Gd3+ → Sm3+ energy transfer efficiency of 75.15%. [ABSTRACT FROM AUTHOR]

The common flower Clitoria ternatea is gifted with organic dyes anthocyanin delphinidin and betalains betacyanin that exhibit broad emission peaks centered at 490 nm and 630 nm. These fresh emission bands in the blue-green and red regions make it a potential white light source that can swap the conventional rare-earth doped phosphor materials. By this line, the extract shows decent emission in its solution state. However, the emission intensity reduces rapidly after a while, owing to the high decay rate of organic dyes in their pure form. Thus, the floral extract is combined with the antioxidant La2O3, reducing the luminescence decay to a noticeable value. The complex formation does not alter the innate La2O3 crystal structure, identified by the XRD peaks, but aids with near-white emission. Upon complex formation, the optical band gap of the host La2O3 falls to the semiconductor range, from 5.1 eV to 2.5 eV. White light emission from La2O3: Clitoria ternatea complex is studied for different extract concentrations and heating conditions, and deemed as a potential replacement for conventional rare-earth doping. [ABSTRACT FROM AUTHOR]

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 BaGa 4 S 7 lattice, preserving its structural integrity. Upon blue light excitation, BaGa 4 S 7 :Eu2+ manifests a robust green emission attributed to Eu2+ ions, showcasing a peak wavelength near 526 nm. The quantum yield (QY) of BaGa 4 S 7 :Eu2+ is remarkably high, registering at 74.8 %. Moreover, the temperature-dependent luminescence properties of BaGa 4 S 7 :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, BaGa 4 S 7 :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. [ABSTRACT FROM AUTHOR]

Abstract The common flower Clitoria ternatea is gifted with organic dyes anthocyanin delphinidin and betalains betacyanin that exhibit broad emission peaks centered at 490 nm and 630 nm. These fresh emission bands in the blue-green and red regions make it a potential white light source that can swap the conventional rare-earth doped phosphor materials. By this line, the extract shows decent emission in its solution state. However, the emission intensity reduces rapidly after a while, owing to the high decay rate of organic dyes in their pure form. Thus, the floral extract is combined with the antioxidant La2O3, reducing the luminescence decay to a noticeable value. The complex formation does not alter the innate La2O3 crystal structure, identified by the XRD peaks, but aids with near-white emission. Upon complex formation, the optical band gap of the host La2O3 falls to the semiconductor range, from 5.1 eV to 2.5 eV. White light emission from La2O3: Clitoria ternatea complex is studied for different extract concentrations and heating conditions, and deemed as a potential replacement for conventional rare-earth doping.

A series of Eu3+-doped self-activated Zn3(VO4)2 (x = 0.0, 2.0, 4.0, 6.0, 8.0 and 10.0 mol%) phosphors have been successfully synthesized by a high-temperature solid-state reaction method. Powder X-ray diffraction patterns of the samples were measured, indicating the successful formation of phosphors with orthorhombic crystal structure. Field emission scanning electron microscopy was used to evaluate the morphology and particle size of the prepared samples, and the composition was analysed by energy X-ray dispersion technique. In addition, prepared samples were analysed by characterization techniques such as transmission electron microscopy, Fourier transform infrared spectroscopy, UV diffuse reflectance spectroscopy and photoluminescence (PL). The PL properties of prepared samples show green–red emission at 395 nm excitation and strong red emission at 467 nm excitation. Under 395 nm excitation, PL emission shows broad green emission band due to self-luminescence properties of vanadate ions. With the doping of Eu3+ ions, (VO4)3– ions transfer their energy to Eu3+ ions. The highest red emission intensity was observed in 8 mol% Eu3+ concentration. The CIE spectral coordinates and colour-correlated temperature of the as-prepared Zn3(VO4)2:Eu3+ phosphors were studied in detail at various Eu3+ concentrations. The obtained PL results demonstrate that the as-prepared Zn3(VO4)2:Eu3+ phosphors can be investigated as green–orange–red emitting phosphors in the future for white light-emitting diodes applications. [ABSTRACT FROM AUTHOR]

Highly thermostable RhB@Zr-Eddc composites with the Rhodamine B (RhB) enclosed into the nanocages of Zr-Eddc was synthesized by one-pot method under hydrothermal conditions, whose structure, morphology and stability were characterized through the X-ray powder diffractometry (XRD), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). RhB@Zr-Eddc showed the highly thermal stability up to 550°C and emitted the bright red-light emission at 605 nm, which could highly selective detect the nitrofurazone (NFZ) among eleven other antibiotics in aqueous solution. Furthermore, via combining the RhB@Zr-Eddc with commercial green phosphor (Y3Al5O12:Ce3+, Ga3+), the mixture was encapsulated onto a 455 nm blue LED chip, creating an excellent white light emitting diode (WLED) device with the correlated colour temperature (CCT) of 4710 K, luminous efficiency (LE) of 43.17 lm/w and Color Rendering Index (CRI) of 89.2. [ABSTRACT FROM AUTHOR]

Red-emitting phosphors are crucial for sustainable white-light-emitting diodes (WLEDs) used in lighting. These materials significantly enhance the lighting and backlit display quality of phosphor-converted white LEDs (pc-WLEDs) by overcoming red deficiency. Luminescent properties of rare earth activated fluoride based inorganic compounds are most investigated due to its excellent spectral characteristics. In this paper we report the novel Na2LiAlF6 luminescent host material activated with Eu3+ rare earth ions synthesized by wet chemical method. The spectral analysis revels the excitation spanning in near UV region while emission spectra depict characteristic peaks transitioned in accordance with 5D0 to 7F1 and 7F2. Effect of concentration quenching, Color purity and temperature studied briefly which demonstrates that the prepared red emitting phosphor is useful in various device applications such as phosphor converted White light emitting diodes for fulfilment of red deficiency, solid state lighting, display technology as an essential red component.

[Display omitted] • Novel eye-sensitive Ba 3 Nb 2 O 2 F 12 (H 2 O) 2 :Tb3+/Mn4+ were synthesized by simple co-precipitation strategy. • Red phosphor presents extremely strong ZPL at ∼ 625 nm and high color purity. • Red and green phosphors exhibit inherently outstanding thermal stability and moisture resistance. • Red and green phosphors coated directly on UV chip can achieve white emission. • The fabricated WLED devices show excellent electroluminescent properties. Novel eye-sensitive Ba 3 Nb 2 O 2 F 12 (H 2 O) 2 :Tb3+ green and Ba 3 Nb 2 O 2 F 12 (H 2 O) 2 :Mn4+ red oxyfluoride phosphors with extremely strong absorption in the UV region were designed and synthesized by simple co-precipitation strategy. Particularly, Tb3+ ions were doped in this matrix for the first time, which greatly improves their absorption efficiency in the near ultraviolet region (367 nm) and emits sharp green light (544 nm). In addition, the Ba 3 Nb 2 O 2 F 12 (H 2 O) 2 :Mn4+ red phosphors have strong zero phonon line (ZPL) emission at 625 nm, which is conducive to improving the sensitivity of human eye and color purity. Meanwhile, the optical properties of the red phosphor are significantly enhanced via doping K+ cations as charge compensators. Crystal field environment and nephelauxetic effect of the as-prepared phosphors before and after K+ cation doping were systematically analyzed. Moreover, these synthesized red/green phosphors have good thermal stability and moisture resistance. Remarkably, the as-prepared Ba 3 Nb 2 O 2 F 12 (H 2 O) 2 :5%Mn4+ or K 0.9 Ba 2.1 Nb 2 O 2 F 12 (H 2 O) 2 :5%Mn4+ red phosphors can be directly mixed with the as-synthesized Ba 3 Nb 2 O 2 F 12 (H 2 O) 2 :13%Tb3+ green phosphor coating on 365 nm near-ultraviolet LED chip to package WLED devices with excellent electroluminescence performance. These findings are conducive to opening an avenue for screening the unique structure of optical materials. [ABSTRACT FROM AUTHOR]

Extensive research has been conducted on all-inorganic CsPbI 3 nanocrystals (NCs) due to their exceptional optical properties. In this study, we successfully prepared CoBr 2 -doped CsPbI 3 NCs in Lithium-borosilicate using the conventional melting quenching approach. We investigated the optical characteristics of CsPbI 3 NCs glass doped with varying amounts of CoBr 2. Remarkably, the samples exhibited outstanding water and thermal stability and tunable emission ranging from 702 to 652 nm. Interestingly, the CsPbI 3 NCs glasses doped with CoBr 2 demonstrated significantly enhanced photoluminescence quantum yields (PLQYs), which increased from 8 % to 32 %. Furthermore, by mixing a red CsPbI 3 NCs glass doped with 0.5 mol CoBr 2 and a green CsPbBr 3 under a blue LED chip, we effectively generated a WLED which achieved (0.3341, 0.3360) of chromaticity coordinate (CIE), 5775.35 K of a correlated color temperature (CCT) that close to positive white light (0.330, 0.330) and the color rendering index (CRI) 79.4. This study provides a new technique in the field of metal ion-doped perovskite NCs, providing a valuable reference for future research and demonstrating possible applications in LEDs. [ABSTRACT FROM AUTHOR]

In an effort to obtain a novel cyan‐emitting phosphor, the [K1‐xRbx]3GdSi2O7: yCe3+ materials (x = 0, 0.1, 0.2, 0.3, 0.4, y = 0, 0.005, 0.01, 0.02, 0.03, 0.04) are synthesized via a solid‐state reaction pathway, and their crystal structure and luminescence behaviors are studied systematically. The chemical substitution of Rb+ in the K+ sites can enlarge the K3GdSi2O7 host lattice and help to the blue‐shifting of emission band of Ce3+ ions due to the decreased crystal field splitting effect. It is also confirmed that the Ce3+ ions tend to enter [Gd1O6] and [Gd2O6] polyhedrons simultaneously. Consequently, the [K0.7Rb0.3]3GdSi2O7: Ce3+ phosphor yields a broadband cyan emission centered at 492 nm with the full width at half maximum (FWHM) of ∼115 nm upon 365 nm excitation. The optimal concentration of Ce3+ dopant is determined to be 0.01, and the concentration quenching effect can be attributed to the dipole−dipole interactions. The white light emitting diode (WLED) device fabricated by employing the discovered [K0.7Rb0.3]3GdSi2O7: 0.01Ce3+ phosphor displays a high color rendering index (Ra = 91.7) and a low correlated color temperature (CCT = 3749 K). This work may promote the development of cyan phosphors for near ultraviolet‐converted WLEDs with high performance. [ABSTRACT FROM AUTHOR]

A series of Ca 3 Y 2 Ge 3 O 12 : xTb3+, yEu3+ (CYGO) phosphors were prepared by the high-temperature solid-phase reaction method. The physical phases, luminescence properties, and energy transfer of the samples were systematically analysed and discussed by XRD and fluorescence spectroscopy. Under the excitation at 377 nm, the CYGO: xTb3+ phosphor emits green light, and the concentration quenching point of Tb3+ ions is x = 0.24. The fluorescence intensity of Tb3+ ions decrease with the increase of the concentration of Eu3+ in CYGO: xTb3+, yEu3+ phosphors, the fluorescence intensity of Eu3+ ions increase rapidly, and the luminescence colour changes from green to red with the increasing of the concentration of Tb3+ at a certain concentration of Tb3+, the luminescence colour changes from green to red, confirm the existence of an energy transfer process between Tb3+ and Eu3+. The energy transfer mechanism is quadrupole-quadrupole interaction. The quantum yield is as high as 95.45%. Under the excitation of the UV-LED chip at 370 nm, the LED based on CYGO:0.24 Tb3+, 0.08Eu3+ phosphors have a R a of 86.7, low CCT of 4917 K and CIE coordinate of (0.3498,0.3789), so the CYGO: xTb3+, yEu3+ phosphors have a potential for application in the field of UV-near-UV white LEDs. has a certain application potential. [ABSTRACT FROM AUTHOR]

We present double-perovskite molybdate with the formula of Ba2MgMoO6 doped with Sm3+ ions as a potential red phosphor to improve the color characteristics of white-light-emitting dioded (wLEDs). The new orange–red phosphor was synthesized using the co-precipitation (CP) method, and then its structural and spectroscopic properties were determined. Red emission at 642.6 nm dominates, which results from the electric dipole (ED) transition of the 4G5/2 → 6H9/2 type, and the materials are characterized by short luminescence decay times. BMM:Sm3+ is, to our best knowledge, the clearest example of dominant red emission of Sm3+ resulting from the location of the dopant in octahedral sites of high-symmetry cubic structure. In the sample containing 0.1% Sm3+, Sm3+ ions are located in both Mg2+ and Ba2+ sites, while at higher concentrations the Ba2+ site is less preferable for doping, as a result of which the emission becomes more uniform and single-site. The relative sensitivity calculated from FIR has a maximum of 2.7% K−1 at −30 °C and another local maximum of 1.6% K−1 at 75 °C. Such value is, to the best of our knowledge, one of the highest achieved for luminescent thermometry performed using only Sm3+ ions. To sum up, the obtained materials are good candidates as red phosphor to improve the color characteristics of wLEDs, obtaining a color-rendering index (CRI) of 91 and coordinated color temperature (CCT) of 2943 K, constituting a warm white emission. In addition to this, a promising precedent for temperature sensing using high-symmetry perovskite materials is the high sensitivity achieved, which results from the high symmetry of the BMM host. [ABSTRACT FROM AUTHOR]

To address the issue of the lack of red light in traditional Ce3+: YAG-encapsulated blue LED white light systems, we utilized spark plasma sintering (SPS) to prepare spinel-based Cr3+-doped red phosphor ceramics. Through phase and spectral analysis, the SPS-sintered ZnAl2O4: 0.5%Cr3+ phosphor ceramic exhibits good density, and Cr3+ is incorporated into [AlO6] octahedra as a red emitting center. We analyzed the reasons behind the narrow-band emission and millisecond-level lifetime of ZAO: 0.5%Cr3+, attributing it to the four-quadrupole interaction mechanism as determined through concentration quenching modeling. Additionally, we evaluated the thermal conductivity and thermal quenching performance of the ceramic. The weak electron-phonon coupling (EPC) effects and emission from antisite defects at 699 nm provide positive assistance in thermal quenching. At a high temperature of 150 °C, the thermal conductivity reaches up to 14 W·m−1·K−1, and the 687 nm PL intensity is maintained at around 70% of room temperature. Furthermore, the internal quantum efficiency (IQE) of ZAO: 0.5%Cr3+ phosphor ceramic can reach 78%. When encapsulated with Ce3+: YAG for a 450 nm blue LED, it compensates for the lack of red light, adjusts the color temperature, and improves the color rendering index (R9). This provides valuable insights for the study of white light emitting diodes (WLEDs). [ABSTRACT FROM AUTHOR]

The study is dedicated to investigation of the structural, luminescent and photoconversion properties of epitaxial converters based on the single crystalline films of Ce3+ doped Ca3Sc2Si3O12 (CSSG:Ce) garnet. These SCFs with different thicknesses were grown using the liquid phase epitaxy method onto: (i) undoped Gd3Ga2.5Al2.5O12 (GAGG (2.5)) substrates; (ii) Ce3+ doped Gd3Ga2.5Al2.5O12 (GAGG:Ce (2.5) and Gd3Ga3Al2O12 (GAGG:Ce (3) substrates. For the first time, we have examined the phosphor conversion properties of the mentioned film and film-crystal converters under the excitation of a blue LED. We have established a trend line in the color coordinate diagram by systematically varying the film thickness in the 2–30 μm, 17–22 μm and 7–22 μm ranges for CSSG:Ce film/GAGG (2.5) crystal, CSSG:Ce film/GAGG:Ce (2.5) crystal and CSSG:Ce film/GAGG:Ce (3) crystal composite converters, respectively.

Through employing the solid-state process under significant temperature, we produced a sequence of single-element radiation-adjustable phosphors Ca8MgR(PO4)7:Eu2+,Mn2+ or CaMg:EM (R = La, Y), and thoroughly analyzed the crystalline arrangement, photoluminescence (PL), PL excitation (PLE), as well as the degrading period. The findings suggest that Ca8MgLa(PO4)7:Eu2+,Mn2+ could be a green contender to be used within close ultraviolet-chip white light-emitted diode (WLED) devices. It is possible to change the emitting green hue from Ca8MgLa1-xYx(PO4)7 treated with Eu2+ to cyan by adjusting the La3+/Y3+ proportion for the purpose of lowering the crystal field potency. Furthermore, power shift among Eu2+ and Mn2+ would be used to create a conventional one-stage white CaMg:EM having a CIE hue coordinate shown as (0.330, 0.328). The power transmission process was shown in the form of resonant dipole-quadrupole nature. In addition, we also computed the critical range. The white-emitting single-composition CaMg:EM was effectively coated above one close ultraviolet chip under 375 nm, indicating that it may become a strong choice of phosphor within close ultraviolet WLED devices.

In recent years, all-inorganic cesium lead halide perovskite quantum dots have emerged as promising candidates for various optoelectronic applications, including sensors, light-emitting diodes, and solar cells, owing to their exceptional photoelectric properties. However, their commercial utilization has been limited by stability issues. In this study, we addressed this challenge by passivating the surface defects of CsPbBr3 quantum dots using indium acetate, a metal–organic compound. The resulting CsPbBr3 quantum dots exhibited not only high photoluminescence intensity, but also a remarkably narrow half-peak width of 19 nm. Furthermore, by embedding the CsPbBr3 quantum dots in ethylene-vinyl acetate, we achieved stretchability and significantly enhanced stability while preserving the original luminous intensity. The resulting composite film demonstrated the potential to improve the power conversion efficiency of crystalline silicon solar cells and enabled the creation of excellent white light-emitting diodes with coordinates of (0.33, 0.31). This co-passivation strategy, involving surface passivation and polymer packaging, provides a new idea for the practical application of CsPbBr3 quantum dots. [ABSTRACT FROM AUTHOR]

The red-emitting phosphor Sr2YNbO6: x Eu3+ and the orange-red-emitting phosphor Sr2YNbO6: y Sm3+ have been synthesized by the high-temperature solid-state method. All samples were thoroughly tested for phase purity, microscopic morphology, photoluminescence properties, thermal stability, and Commission Internationale de l'Eclairage (CIE) chromaticity coordinates. The results show that there is no impurity phase in the sample, the convergence factors are all less than 10%, the Eu3+ and Sm3+ ions participating in the mixed arrangement are consistent with the target doping concentration, and the microscopic particles are uniform and full. When the concentration of doped Eu3+ and Sm3+ reaches 0.25 mol and 0.02 mol, respectively, the luminous intensity is the best, and it emits red light at 610 nm and orange-red light at 606 nm under excitation at 467 nm and 406 nm, respectively. Dipole-dipole interactions are responsible for the concentration quenching. The quantum efficiencies (QE) are 68.95% and 53.91%, respectively. They all have excellent thermal stability with luminescence intensity at 425 K of 67.3% and 84.8% of room temperature, respectively. Color reproduction (Ra) and comfortable color rendering index (R9). Ra reached 91 and 88, respectively, and R9 reached 73.4 and 65.8, respectively, for the combined white light-emitting diode (WLED) prepared with commercial phosphors and experimental samples. All the results suggest that Sr2YNbO6: RE (Eu3+, Sm3+) can be used as a red phosphor replacements in WLEDs. [ABSTRACT FROM AUTHOR]

The cyan-emitting BaSi 2 O 2 N 2 :Eu2+ phosphor is a promising narrow-band and high-efficiency luminescent material used in wide-color-gamut white light-emitting diodes (wLEDs). However, its serious degradation under thermal attacks hinders its practical applications and needs to be improved. Herein, we proposed to deposit a nano-sized Al 2 O 3 film around each BaSi 2 O 2 N 2 :Eu2+ particle through atomic layer deposition (ALD) in a fluidized bed reactor to improve its thermal stability. Thermal gravimetric analysis results showed that the Al 2 O 3 layer with a thickness of only 11 nm had an obvious anti-oxidization effect, by which the oxidation temperature in air of the Al 2 O 3 coated phosphor was largely increased from ∼550 to ∼750 °C. Moreover, the Al 2 O 3 coated phosphor remained 93% of its luminescence intensity in comparison to 73% of the uncoated one when degraded under water-steam at 200 °C for 24 h. The oxidization of both the BaSi 2 O 2 N 2 host matrix and the doped Eu2+ ions was reduced by the Al 2 O 3 layer. Meanwhile, the wLEDs fabricated with the Al 2 O 3 coated phosphor showed a luminous flux of 3 times higher than that of the uncoated one when aged under 100 mA for 300 h. The greatly improved thermal degradation property of BaSi 2 O 2 N 2 :Eu2+ phosphor and the reliability of the wLEDs indicate that the ALD approach could be a feasible route to produce uniform and nano layers on phosphors and enhance their stability. [ABSTRACT FROM AUTHOR]

The tunable 5 d-4f luminescence of Eu2+ is of great application value, but it is still full of challenges in terms of luminescence efficiency, thermal stability and precise tuning of luminescence colors. In this work, we synthesized a series of Rb 2-x Cs x CaP 2 O 7 :0.015Eu2+ phosphors based on the equivalent substitution strategy, allowing a certain proportion of Cs+ to replace Rb+ sites. By optimizing the Rb/Cs ratio, the structural symmetry of the [CaO 6 ] octahedra can be enhanced, providing a high-stability and high-symmetry localized crystal field environment for the high efficiency luminescence of Eu2+. The experimental results confirmed that the broad-spectrum orange light emission could be achieved in Rb 0·5 Cs 1·5 CaP 2 O 7 :0.015Eu2+, and the integrated luminescence intensity was 6.9 times higher than that of Rb 2 CaP 2 O 7 :0.015Eu2+. Moreover, the luminescence intensity at 150 °C reached 93.3% of its room-temperature value. Using the synthesized phosphor as orange component, a white LED was assembled and a high-quality white light emission with Ra = 87.8 was achieved. These results suggest that rationally tuning the local structural symmetry around Eu2+ is an effective strategy to develop high-performance Eu2+-activated phosphors. [ABSTRACT FROM AUTHOR]

The phosphor-converted white light-emitting diode (WLED) has received tremendous attention as a promising alternative to traditional light sources in lighting and displays. Herein, a novel broadband red emitter Ca2Sr(PO4)2:Mn2+ was successfully designed and synthesized based on the Sr-alloying and Mn-doping of Ca3(PO4)2. The phase purity of the materials was verified by x-ray diffraction (XRD) analyses, while a scanning electron microscope (SEM) coupled with an energy-dispersive spectrometer (EDS) was employed to confirm the uniform dopant distribution. XRD Rietveld refinements were further performed to clarify the site occupation of alloying Sr and the Mn dopants. Effective site engineering confined the Mn dopants in a highly symmetric Ca5 site and excluded the immersion of Sr, leading to an extraordinarily long fluorescence lifetime. Density functional theory (DFT) simulations also revealed the good potential of the materials as host matrices for activators such as Mn2+. Finally, Ca2Sr(PO4)2:Mn2+ was used to fabricate a WLED prototype based on a near-ultraviolet (n-UV) commercial LED chip, which realized a warm white-light emission and high color rendering index (Ra) of 82.9. This WLED was able to survive the long-term stability test while maintaining high luminous efficacy of ~ 60 lm/W within 20 h, showing its great potential in practical applications. [ABSTRACT FROM AUTHOR]

In the development of novel phosphors for solid‐state light applications, the suitable excitation peak matching with blue LED chip was usually neglected. However, the excitation peak of phosphors was strongly related to the Stocks shift, crystal field splitting, and centroid shift. Here, an environmentally friendly borate phosphor KSr4B3O9: Eu2+ with the maximum excitation peak position at ∼460 nm was prepared in a quite mild synthesis condition. With a blue light excitation, KSr4B3O9: Eu2+ phosphors could emit a bright yellow light centered at ∼560 nm, which could be attributed to the drastic centroid shift and strong crystal field splitting. The strong electron cloud overlaps between Eu–O and the high electron density on the O atom turned out to be the main reason that induces the strong nephelauxetic effect. In addition, the strong crystal field splitting was benefited to the relatively short average Sr–O distance and the large Sr–O distances distribution range from ∼2.23 to 2.96 Å. Meanwhile, the Eu2+ occupation of all the Sr2+ sites in KSr4B3O9 host identified by Rietveld refinement, cryogenic emission spectra, and Eu3+ fluorescent probe gave another evidence to the wide absorption region. The final WLED device and three‐dimensional colorful artwork were fabricated and displayed to suggest a potential application in the solid‐state lighting field and some expressions of esthetic concepts. [ABSTRACT FROM AUTHOR]

This work is dedicated to study the synthesis processes and luminescence properties of micro-crystalline powder phosphors of Ce3+ and Mn2+ doped Ca2YMgScSi3O12 garnets (CYMSSG:Ce and CYMSSG:Ce,Mn) The photoluminescence emission spectra and decay kinetics confirm the formation of Ce3+ multicenters in the CYMSSG:Ce powder phosphor due to local inhomogeneity of the different dodecahedral positions and presence of the energy transfer between high-energy and low energy Ce3+ emission centers in this garnet. The effective Ce3+ to Mn2+ energy transfer process is observed in CYMSSG:Ce, Mn phosphors resulting in the redshift of the emission spectra in comparison with CYMSSG:Ce counterpart. We have shown that CYMSSG:Ce and CYMSSG:Ce, Mn powder phosphors can be used as an efficient photoconverter (PC) for creation of the high-power white LEDs (WLEDs). The prototypes of PC-WLEDs, based on 450 nm emitting blue LED and planar layers of CYMSSG:Ce and CYMSSG:Ce, Mn microcrystalline powder phosphors, embedded in the epoxy resin, were prepared and their photoconversion properties were investigated as well.

The construction of high luminous quality (quantum efficiency, color purity, etc.) cyan emission phosphor has a milestone significance for improving lighting quality and expanding the application fields of phosphor. Here, a kind of cyan emission phosphor Ca 8 ZnY(PO 4) 7 :Eu2+ is prepared by using β-Ca 3 (PO 4) 2 as prototype according to structural engineering strategy. Through the activation of Eu2+ and the energy transfer from Eu2+ to Mn2+ in Ca 8 ZnY(PO 4) 7 , the applications of WLEDs and optical anti-counterfeiting are realized. Excited at 320 nm, the central peak of Ca 8 ZnY(PO 4) 7 :Eu2+ spectra is at around 490 nm, the full width at half maximum is ∼80 nm, and the internal quantum efficiency is up to 51.52 %. Based on Rietveld refinement of XRD data and Gaussian fitting, three luminescence centers are identified. The maximum energy transfer efficiency from Eu2+ to Mn2+ is 51.05 %, and the energy transfer type is also determined by calculation. With the regulation of Mn2+ concentration, the luminous color of the series phosphor transitions from cyan to white and finally to red. The prepared phosphors possess certain thermal stability, which can not only compensate the cyan gap in the commercial phosphor combination LEDs, but also be used as phosphor raw material for single-phase WLEDs. In addition, the optical anti-counterfeiting films prepared by mixing the prepared phosphors with polyvinyl alcohol have the advantages of transparency, flexibility and rapid response, exhibiting great potential applications in the fields of optical anti-counterfeiting, information encryption and even criminal investigation. In summary, the prepared phosphors have the potential of multi-functional application in the field of high-quality lighting and anti-counterfeiting. [Display omitted] • A novel cyan light emission phosphor Ca 8 ZnY(PO 4) 7 :Eu2+ was prepared. • Ca 8 ZnY(PO 4) 7 :Eu2+ phosphor has a high cyan color purity. • Ca 8 ZnY(PO 4) 7 :Eu2+ phosphor has high quantum efficiency. • With the participation of Ca 8 ZnY(PO 4) 7 :Eu2+, the Ra of WLED can reach 96.8, and the CCT can reach 4461 K. • The application demonstration in optical anti-counterfeiting, information encryption and criminal investigation is provided. [ABSTRACT FROM AUTHOR]

[Display omitted] • Organic cuprous clusters were synthesized by antisolvent vapor-assisted crystallization. • Photoluminescence was tunable by adjusting ratio of raw materials due to vacancy defects changing. • Two charge transfer paths exist in the IPPCuI 2. • Superior X-ray scintillation performances exhibit in DR and CT. • Single-component WLED based on IPPCuI 2 has high CRI and stability. Low-dimensional cuprous clusters demonstrate fascinating luminescent properties due to their uniquely diversified charge transfer excited states, which imply it could be ideal candidate for multifunctional applications, such as X-ray scintillators and white light emitting diodes (WLED). However, it is still challenge for low-dimensional cuprous clusters that how to regulate the emission performance to meet the requirements of the specific applications. In this work, we prepared a series of luminescent organic cuprous iodide clusters, (IPP)CuI 2 and (IPP) 2 CuI 3 , which show tunable emission property by simply component regulation. The (IPP)CuI 2 with IPP: CuI = 1: 0.75 show the best scintillator property with super-low detection limit of 62.29 nGy/s and high light yields of 75793.83 photons/MeV which is far beyond most organic copper halide scintillators. A series of clear digital radiography (DR) with high spatial resolution of 10.2 lp/mm and a reconstructed 3D model based on computed tomography (CT) were successfully obtained by the prepared scintillation screen. Moreover, the single-component WLED based on accurately component regulation (IPP)CuI 2 with IPP: CuI = 1: 0.99 exhibits pure white emission with a high CRI (color rendering index) of 82. The luminescence mechanism of charge transfer excited states in tunable emission (IPP)CuI 2 was also investigated. Our works not only provide a kind of ideal materials applied for high-performance single-component WLED and scintillator but also reveal the large potential of low-dimensional organic cuprous halides as luminescent material for multifunctional applications. [ABSTRACT FROM AUTHOR]

Two series of new Sb3+ doping-(TAEA)InCl 6 ·Cl·4H 2 O: x Sb3+ and (TETA)InCl 6 ·Cl·H 2 O: x Sb3+ organic–inorganic hybrid metal halide single crystals were synthesized and characterized. The two series of compounds achieved fast digital encryption and decryption functions and prepared high-performance WLEDs. [Display omitted] • A Triethylenetetramine is employed for synthesis a series of new organic–inorganic hybrids (TAEA)InCl 6 ·Cl·4H 2 O:Sb3+ and (TETA)InCl 6 ·Cl·H 2 O:Sb3+. • (TAEA)InCl 6 ·Cl·4H 2 O:Sb3+ achieves rapid encryption, decryption and anti-counterfeiting at the appropriate temperature. • Fs-TA spectroscopic studies and DFT calculations provide in-depth understanding of the photophysical mechanisms. • WLED based on (TETA)InCl 6 ·Cl·H 2 O:Sb3+ can exhibit a high luminous efficiency of 43.72 lm/W, with CRI and CCT of 90.5 and 5415 K respectively. Lead-free metal halides with thermally induced reversible fluorescence transitions are promising smart optoelectronic materials. However, it is challenging to obtain such materials with reversible and fast fluorescent thermochromism at relatively low temperatures. Herein, two series of new zero-dimensional (0-D) hybrid perovskite indium chlorides doped with Sb3+ are synthesized and characterized, namely (TAEA)InCl 6 ·Cl·4H 2 O: x Sb3+ (1: x Sb3+) and (TETA)InCl 6 ·Cl·H 2 O: x Sb3+ (2: x Sb3+) (TAEA = quadruply protonated tris(aminoethyl)amine; TETA = quadruply protonated triethylenetetramine; x = 0 − 15 %). Compound 1: 0.5 %Sb3+ displays green broadband emission with photoluminescence quantum yield (PLQY) of 44.4 %, while compound 2: 1 %Sb3+ produces yellow emission with PLQY of 73.46 %. A reversible transition between green and orange light emission for 1: 0.5 %Sb3+ can be triggered by thermal stimulation; such photoluminescence (PL) color switching happens with a fast response time of 20 s and a low transition temperature of 333 K. In addition, the materials combining compounds 2: 1 %Sb3+ and 1: 0.5 %Sb3+ can achieve complex digital encryption and decryption upon heating. Furthermore, due to its excellent luminous efficiency, the 2: 1 %Sb3+ is employed as yellow phosphor for white light-emitting diode (WLED). The WLED shows a CRI of 90.5 and a CCT of 5415 K, superior to most WLEDs based on hybrid metal halides. Finally, the impact of forming the self-trapped excitons state and complex PL mechanism of compound 1: 0.5 %Sb3+ are investigated through DFT calculations and femtosecond transient absorption techniques. This work provides new insights into the design of hybrid metal halides with multiple optical properties, paving the way to obtaining materials for multiple optical applications. [ABSTRACT FROM AUTHOR]

This work is dedicated to the crystallization and luminescent properties of a prospective Ca2YMgScSi3O12:Ce (CYMSSG:Ce) micropowder (MP) phosphor converter (pc) for a white light–emitting LED (WLED). The set of MP samples was obtained by conventional solid-phase synthesis using different amounts of B2O3 flux in the 1–5 mole percentage range. The luminescent properties of the CYMSSG:Ce MPs were investigated at different Ce3+ concentrations in the 1–5 atomic percentage range. The formation of several Ce3+ multicenters in the CYMSSG:Ce MPs was detected in the emission and excitation spectra as well as the decay kinetics of the Ce3+ luminescence. The creation of the Ce3+ multicenters in CYMSSG:Ce garnet results from: (i) the substitution by the Ce3+ ions of the heterovalent Ca2+ and Y3+ cations in the dodecahedral position of the garnet host; (ii) the inhomogeneous local environment of the Ce3+ ions when the octahedral positions of the garnet are replaced by heterovalent Mg2+ and Sc3+ cations and the tetrahedral positions are replaced by Si4+ cations. The presence of Ce3+ multicenters significantly enhances the Ce3+ emission band in the red range in comparison with conventional YAG:Ce phosphor. Prototypes of the WLEDs were also created in this work by using CYMSSG:Ce MP films as phosphor converters. Furthermore, the dependence of the photoconversion properties on the layer thickness of the CYMSSG:Ce MP was studied as well. The changes in the MP layer thickness enable the tuning of the white light thons from cold white/daylight to neutral white. The obtained results are encouraging and can be useful for the development of a novel generation of pcs for WLEDs. [ABSTRACT FROM AUTHOR]

This work presents various essential features and design aspects of a single-inductor, common-output, and multi-string White Light Emitting Diode (WLED) driver for low-power portable devices. High efficiency is one of the main features of such a device. Here, the efficiency improvement is achieved by selecting the proper arrangement of WLEDs and a proper sensing-circuit technique to determine the minimum, real-time, needed output voltage. This minimum voltage necessary to activate all WLEDs depends on the number of strings and the forward voltage drops among the WLEDs. Advanced CMOS technology is advantageous in mixed-signal environments such as WLED drivers. However, this process suffers from low on-resistance, which degrades the accuracy of the current sinks. To accommodate the above features and mitigate the low node process issue, a boost-converter that is single output with a load of a three-string arrangement, with 6 WLEDs each, is presented. The designed driver has an input voltage range of 3.2–4.2V. The proposed solution is realized with ultra-low power consumption circuits and verified using ADS tools utilizing 40 nm 1P9M TSMC CMOS technology. An inter-string current accuracy of 0.2% and peak efficiency of 91% are achieved with an output voltage up to 25 V. The integrated WLED driver circuitry enables a high switching frequency of 1MHz and reduces the passive elements' size in the power stage. [ABSTRACT FROM AUTHOR]

[Display omitted] Doping Mn2+ into CsPbCl 3 nanocrystals (NCs) yields strong orange emission, while the related emission in Mn2+ doped CsPbBr 3 NCs is impaired seriously. This is mainly ascribed to back energy transfer from the Mn2+ dopant to the host. Doping Mn2+ into perovskites with multiple-quantum-well (MQW) structures may address this issue, where the energy funnels ensure a rapid energy transfer process, and thus resulting in a high photoluminescence quantum yield (PLQY). Here, we have developed an Ag+ assisted Mn2+ doping method in which Mn2+ can be easily doped into Br-based MQW perovskites. In this MQW perovskites, both nanoplatelets (NPLs) and NCs were formed simultaneously, where efficient energy transfer occurred from the NPLs with a higher energy bandgap to the NCs with a smaller energy bandgap, and then to the Mn2+ dopants. White lighting solution with a PLQY up to 98% has been acquired by altering the experimental parameters, such as reaction time and the Pb-to-Mn feed ratio. The successful doping of Mn2+ into CsPbBr 3 host has great significance and shows promising application for next-generation white lighting. [ABSTRACT FROM AUTHOR]

Exploring novel efficient phosphors for lighting and display has always been an important and meaningful work for researchers. Herein, a novel efficient blue‐emitting phosphor, Eu2+ doped barium‐containing silicate fluoride NaBa3Si2O7F, was prepared by solid‐state method. The phosphor can produce bright blue light peaked at 452 nm with full‐width at half‐maximum about 57 nm under near‐UV light excitation, and it exhibits a high internal quantum yield about 76.23%. The temperature‐dependent photoluminescence spectra show that this phosphor owns good thermal stability, and the emission intensity at 425 K is 67% of that at room temperature. The outstanding data of fabricated device demonstrate that the blue phosphor has large possibility of practical application for white light‐emitting diode. Furthermore, the phosphor also possesses good cathodoluminescence properties under various accelerating voltage with different probe currents, indicating its potential application in field emission displays. [ABSTRACT FROM AUTHOR]

Micro-light-emitting diodes (μ-LEDs) are the significant to next-generation displays, making it possible to offer innovative applications in virtual/augmented reality, mobile phones, ultrahigh-definition televisions, and wearable devices that meet the individualized needs of advanced applications. Due to the limited absorption cross-section, traditional color conversion phosphor cannot provide adequate brightness and yield to sustain high-resolution screens when LED chip sizes decrease below 20 ​μm. Due to their exceptional luminescence efficiency, color tunability, narrow bandwidth, quantum dot (QD) materials are projected to fill this gap, providing a strong full-color solution for μ-LED displays. The eye-catching optical property of perovskite quantum dots (PQDs) and their cost-effective manufacturing have attracted a wide range of industries and academic institutions. In spite of their unprecedented success, the lack of stability is a prevalent concern in all perovskite-related domains, and it restricts their wide applicability. The structural and irradiant influences on perovskites' optoelectronic characteristics and stability is the main issue for the present time. Hence, the present graphical review summarizes all the intrinsic and extrinsic aspects for the degradation of PQDs. An analysis of the sources of the instability of PQDs, including structural instability, interfacial instability, and atmospheric instability is carried out in details. We will conclude with some suggestions to improve the stability of the PQDs and device performance. By exploring the research pursuit of instability and related present and future mitigation strategies, the present graphical review will certainly open new perspectives on PQDs.

The blue phosphor material in trichromatic phosphors for white light emitting diodes (WLED) has a great application prospect. Therefore, the silicate blue luminescent material BaCaSiO4:Eu2+, Gd3+ for WLED was prepared by combustion method. Using urea as combustion agent, the optimum sintering temperature and sintering time of primary sintering and secondary sintering were studied. The main emission peak of the luminescent material is located at 499nm, which was the transition emission peak of 4f65d¹→4f7 of Eu2+, and the luminescence properties of silicate luminescent material could be enhanced by doping a certain amount of Gd3+. The color of light emitted from the luminescent material was pure blue according to the color coordinates obtained from the emission spectrum. [ABSTRACT FROM AUTHOR]

Based on blue LED chips to excite Ce-doped yttrium aluminum garnet (YAG: Ce3+) yellow phosphors, InP/ZnS green-emitting quantum dots (QDs) and InP/ZnSe/ZnS red-emitting QDs are used as light conversion materials for WLEDs to improve the color rendering index (CRI) of the device and improve its color coordinates. We have proven this in previous work. But in the previous work, we only studied the CRI of the driving current from 5 mA to 100 mA. The CRI and the Commission International de L'Eclairage (CIE) chromaticity coordinates of the WLED device prepared before is not ideal under high current conditions. The emission peak position of InP/ZnSe/ZnS red-emitting QDs we used in previous work is 605nm. In this article, we adjusted the emission peak position of InP/ZnSe/ZnS red-emitting QDs to 611nm, and prepared WLED in the same way, which improved the problem that the CRI of WLED devices decreases rapidly and the chromaticity coordinates change greatly under high current conditions. The CRI of prepared WLED device in this article was increased to 91.0, the CIE chromaticity coordinates is (0.3365, 0.3334), and the correlated color temperature (CCT) is 5313 K. We also tested the dependence of the electroluminescence (EL) spectrum, CRI, CCT and chromaticity coordinates of the prepared WLED device on the current. Compared with the prepared WLED device before, the CRI of the WLED device prepared in this article has always remained above 90, hovering between 90 ~ 91, very stable. The chromaticity coordinate distribution is also very concentrated, the amplitude of the offset black body radiation is small, and it shows excellent color rendering and stable working performance. A 30-day aging test was performed on the prepared WLED device.

Abstract Perovskite quantum dots (QDs) have been widely used in white light-emitting diodes (WLEDs), due to their high quantum yield (QY), tunable bandgap, and simple preparation. However, the red-emitting perovskite QDs are usually containing iodine (I), which is not stable under continuous light irradiation. Herein, perovskite-based WLED is fabricated by lead-free bismuth (Bi)-doped inorganic perovskites Cs2SnCl6 and less-lead Mn-doped CsPbCl3 QDs, which emits white light with color coordinates of (0.334, 0.297). The Bi-doped Cs2SnCl6 and Mn-doped CsPbCl3 QDs both show excellent stability when kept in the ambient air. As benefits from this desired characteristic, the as-prepared WLED shows excellent stability along with operating time. These results can promote the application of inorganic perovskite QDs in the field of WLEDs.

Two cyan-emitting phosphors with different bandwidths were successfully synthesized through the high-temperature solid-state method in a reducing atmosphere. The crystal structures, morphologies, and luminescence properties of the as-prepared phosphors were investigated. The Rietveld refinements of the powder X-ray diffraction (XRD) data demonstrated the single phase of the samples, and two crystallographic sites of La3+ were observed in the crystal structure. Under the excitation of UV light, both Ba 0.45 Ca 2.5 La 6 (SiO 4) 6 : 0.05 Eu2+ and Ba 1.45 Ca 1.5 La 6 (SiO 4) 6 : 0.05 Eu2+ phosphors emitted cyan light due to the 4f65 d1→4f7 transitions of the Eu2+ ion. The emission spectra could be well fitted by two component Gaussian peaks corresponding to two different coordination environments of the Eu2+ ions. The temperature-dependent photoluminescence spectra show a large difference on the thermal stability between the two phosphors. The two phosphors exhibit effective absorption of near-UV light and their internal quantum efficiencies (IQEs) were calculated as 31.5% and 42.4% under 295 nm UV-light excitation. The experimental results indicate that the novel cyan phosphors might have potential applications in white light-emitting diodes (LEDs) based on the near-UV LED chip. [ABSTRACT FROM AUTHOR]

As is well known, a way to obtain a high color resolution and saturation of a liquid crystal display and thereby obtain a higher visual accuracy and comfort in the coming 5G era remains an urgent challenge. In the present study, a new type of phosphor composite material doped with Ln3+ ions provides a promising alternative to the color filters used in White light-emitting diodes (WLEDs), achieving a better performance regarding the realization of a wider color gamut. The advantages of this composite material are illustrated through an abundant phase and morphology analysis along with a discussion regarding the X-ray photoelectron spectroscopy of the valence bond of Ce ions, which maintain the luminescence properties of the phosphor while providing a stable and solid amorphous environment. An improved spectral performance was obtained through color filtering at 580 nm along with the regulating effects of red, green, and blue emissions according to the doped Ln3+ ions. Notably, we fabricated a high-performance WLED based on a Ln3+-doped PiG with a correlated color temperature of 5037 K, color rendering index of 72.8, and high color gamut of 91.97%, providing a new choice for the development of luminescence materials with a high color resolution and saturation. [ABSTRACT FROM AUTHOR]

Langbeinite‐type compounds are a large family that include phosphates, sulfates and arsenates, and which are accompanied by interesting physical properties. This work reports a new disordered langbeinite‐type compound, K2GdHf(PO4)3 [dipotassium gadolinium hafnium tris(phosphate)], and its structure as determined by single‐crystal X‐ray diffraction. Theoretical studies reveal that K2GdHf(PO4)3 is an insulator with a direct band gap of 4.600 eV and that the optical transition originates from the O‐2p→Hf‐5d transition. A Ce3+‐doped phosphor, K2Gd0.99Ce0.01Hf(PO4)3, was prepared and its luminescence properties studied. With 324 nm light excitation, a blue emission band was observed due to the 5d1→4f1 transition of Ce3+. The average luminescence lifetime was calculated to be 5.437 µs and the CIE chromaticity coordinates were (0.162, 0.035). One may expect that K2Gd0.99Ce0.01Hf(PO4)3 can be used as a good blue phosphor for three‐colour white‐light‐emitting diodes (WLEDs). [ABSTRACT FROM AUTHOR]

• CsAgCl 2 nanocrystals with excellent optical properties were synthesized. • The moisture-assisted space-confined synthesis effectively limited the size of nanocrystals. • Molecular sieves improved the thermal stability of CsAgCl 2 NCs. Perovskite nanocrystals (NCs) have garnered extensive attention for their excellent photoelectric properties. However, the widespread use of and development of perovskite materials have been hindered by the significant toxicity associated with lead. The exploration of lead-free alternatives, such as silver-based perovskite-derivative NCs, faces difficulties in synthesizing NCs with an average diameter of less than 50 nm owing to their extremely high surface energy. To address these problems, we successfully synthesized lead-free CsAgCl 2 perovskite-derivative NCs with an average diameter as small as 45.22 nm. This was achieved using molecular sieves (MS) as templates for confined space synthesis. Water vapor entered the pores of MS and underwent capillary condensation. The resulting liquid water facilitated the dissolution and diffusion of CsCl, which subsequently reacted with AgCl to produce CsAgCl 2. The as-obtained CsAgCl 2 NCs exhibited a photoluminescence quantum yield (PLQY) of 22 %, with an emission center at 610 nm and a full width at half maximum of 211 nm. These characteristics are indicative of a typical self-trapping exciton (STE) emission material displaying warm white light. When integrated into a white light-emitting diode (WLED), it achieves Commission Internationale de 'Eclairage (CIE) color coordinates of (0.3553,0.3408), a correlated color temperature (CCT) of 4556 K, and a maximum brightness of 316.55 cdm−2. This suggests a promising application prospect for single-component white light illumination. [ABSTRACT FROM AUTHOR]