Light-emitting Diode Devices Research Articles

CaLu2Sc2Al2SiO12:Ce3+ Green Phosphors for High-Quality White LEDs.

Phosphors with broadband green emission are highly desirable for the construction of high-color-rendering warm-white light-emitting diode (LED) devices toward healthy solid-state lighting applications. However, most of the reported green phosphors are subject to an undesirable emission bandwidth and low quantum efficiency. Here, a highly efficient broadband green-emitting garnet phosphor, CaLu2Sc2Al2SiO12:Ce3+ (CLSASO:Ce3+), is successfully synthesized and investigated in detail. Upon excitation of 440 nm blue light, the as-synthesized CLSASO:3%Ce3+ phosphor features a wide bandwidth with a maximum peak situated at 534 nm and a large full width at half-maximum (fwhm) of 114 nm, which is superior to the commercial green phosphor of LuAG:Ce3+ (fwhm = 108 nm). As expected, the optimal CLSASO:3%Ce3+ sample also demonstrates satisfactory internal/external quantum efficiency of 78.3/50.1%, along with suitable CIE color coordinates of (0.3462, 0.5496). Meanwhile, temperature-dependent emission spectra measurements indicate that it retains 46% of the original integral intensity at 423 K against room temperature, together with an excellent color stability of 9.2 × 10-3. Finally, a fabricated blue-light-pumped prototype LED device with the proposed CLSASO:3%Ce3+ green component and another commercial CaAlSiN3:Eu2+ red phosphor delivers a brilliant warm-white light with a desirable color rendering index (Ra = 90.2), an acceptable color temperature of 4047 K and a superior luminous efficiency of 65.6 lm W-1. The findings illustrate that the construction of blue-light-excitable broadband green luminescence conversion material is beneficial for the preparation of a high-color-rendering warm-white LED device for high-quality general lighting applications.

Synergistic Hybrid-Ligand Passivation of Perovskite Quantum Dots: Suppressing Reduced-Dimensionality and Enhancing Optoelectronic Performance.

In terms of surface passivation for realizing efficient CsPbI3-perovskite quantum dot (CsPbI3-PQD)-based optoelectronic devices, phenethylammonium iodide (PEAI) is widely used during the ligand exchange. However, the PEA cation, due to its large ionic radius incompatible with the 3D perovskite framework, acts as an organic spacer within polycrystalline perovskites, leading to the formation of reduced dimensional perovskites (RDPs). Despite sharing the identical 3D perovskite framework, the influence of PEAI on the structure of CsPbI3-PQDs remains unexplored. Here, it is revealed that PEAI can induce the formation of high-n RDPs (n>2) within the CsPbI3-PQD solids, but these high-n RDPs undergo an undesirable phase transition to low-n RDPs, leading to the structural and optical degradation of CsPbI3-PQDs. To address the PEAI-induced issue, we employ triphenylphosphine oxide (TPPO) as an ancillary ligand during the ligand exchange process. The incorporation of TPPO prevents H2O penetration and regulates the rapid diffusion of PEAI, suppressing the formation of low-n RDPs. Moreover, TPPO can passivate the uncoordinated Pb2+ sites, reducing the nonradiative recombination. This hybrid-ligand exchange strategy using both PEAI and TPPO enables realizing efficient and stable CsPbI3-PQD-based light-emitting diode (external quantum efficiency of 21.8%) and solar cell (power conversion efficiency of 15.3%) devices.

Tunable photoluminescence and energy transfer in Dy3+ and Eu3+ co-doped NaCaGd(WO4)3 phosphors for pc-WLED applications.

Elevated temperatures can lead to reabsorption and color drift, compromising the quality of phosphor-converted white light-emitting diode (pc-WLED) devices. To ensure the performance of WLEDs under these conditions, it is essential to develop luminescent materials that maintain stable color. Consequently, there is a pressing need for single-phase white-emitting phosphors with robust chromatic stability. In this work, we synthesize a series of color-tunable NaCaGd(WO4)3 (NCGW) phosphors using conventional solid-state reaction method, co-doping with Dy3+ and Eu3+ in varying ratios. X-ray diffraction, Rietveld refinement and scanning electron microscopy analyses are carried out to identify the phase purity and morphology. The photoluminescence (PL) properties are investigated under excitations of 352 nm and 393 nm. The PL emission spectra and fluorescence decay curves reveal efficient energy transfer between the Dy3+ and Eu3+ ions within the NCGW host, demonstrating tunable PL emission properties through manipulation of this energy transfer. At elevated temperatures of up to 200 °C, the positions of the characteristic emission peaks of Dy3+ and Eu3+ in NCGW phosphors remain essentially unchanged. Although the emission band intensities decrease due to thermal quenching, they retain a significant portion of their initial intensity compared to room temperature levels. For proof-of-concept studies, a single-phase NCGW:0.05%Dy3+-0.05%Eu3+ phosphor is combined with a commercial 365 nm UV chip to create a WLED device prototype. This prototype achieves a color rendering index of 81.7, a correlated color temperature of 4862 K and Commission International de I'Eclairage chromaticity coordinates of (0.35, 0.37), exhibiting comparable or superior colorimetric values to those reported in previous research. The results indicate that Dy3+ and Eu3+ co-doped NCGW phosphors, with their high chromaticity stability, have significant potential for full-spectrum WLED applications.

Uncovering the Performance Enhancing Mechanism of Methanesulfonate Ligands in Perovskite Quantum Dots for Light-Emitting Devices.

Perovskite quantum dots (PQDs) have attracted more and more attention in light-emitting diode (LED) devices due to their outstanding photoelectric properties. Surface ligands not only enable size control of quantum dots but also enhance their optoelectronic performance. However, the efficiency of exciton recombination in PQDs is often hindered by the desorption dynamics of surface ligands, leading to suboptimal electrical performance. In this study, sodium methanesulfonate (NaMeS) was successfully introduced during PQD synthesis and ligand exchange, where the S═O groups effectively interacted with the perovskite components. The NaMeS-modified PQD films exhibited significantly improved surface morphology, radiative recombination efficiency, and carrier mobility. Consequently, Pe-LEDs derived from NaMeS-capped PQDs achieved a remarkable enhancement in performance with a maximum external quantum efficiency of 9.41%. This work thus provides a novel and effective strategy for the development of high-performance PQDs and their applications in LEDs.

Balancing efficiency and color gamut in white organic light-emitting diodes for microdisplay applications by microcavity and color filter conditions

Color filters are applied to white organic light-emitting diode microdisplays to generate red, green, and blue subpixels. By incorporating a microcavity structure, both the efficiency and the color gamut of the device can be significantly improved. Although the length of the cavity can be adjusted for each subpixel, the optical properties of the top electrodes remain consistent across all subpixels. The focus of this study was on optimizing the microcavity structure to accurately realize the colors of each subpixel in white organic light-emitting diodes while accounting for the transmittance characteristics of the color filters. While higher electrode reflectivity improved the color gamut, the optimal electrode structure for efficiency varied for each subpixel. In the case of color filters, increasing the thickness tends to improve the color gamut but reduces efficiency. Therefore, subpixel structures that optimize both the efficiency and color gamut by balancing these factors were investigated in this study. As the red, green, and blue ratio within the emitting layer affects the electroluminescence spectrum of the organic light-emitting diode device, the composition of the emitting layer was also investigated to optimize the color gamut.

Manipulating Electron-Phonon Coupling for Efficient Tin Halide Perovskite Blue LEDs.

Low-dimensional perovskites have opened up a new frontier in light-emitting diodes (LED) due to their excellent properties. However, concerns regarding the potential toxicity of Pb limited their commercial development. Sn-based perovskites are regarded as a promising candidate to replace Pb-based counterparts, while they generally exhibit strong electron-phonon coupling and consequently blue emission quenching at room temperature (RT), thus the Sn-based perovskite blue LED devices have not yet been reported. Herein, the luminescence properties are regulated by assembling a rigid organic skeleton within perovskite structure, and the protonated 4-bromobenzylamine (BrPMA+ = C7H9BrN+) is employed as A site cation to synthesize a 100-oriented 2D perovskite (BrPMA)2SnBr4, which exhibits a strong lattice rigidity via strong intermolecular interaction and consequently weak electron-phonon coupling, achieving the excellent blue PL emission at RT. The high quality (BrPMA)2SnBr4 perovskite thin films are obtained by further inhibiting oxidation and promoting crystallization. Finally, the Sn-based perovskite blue emission LED is successfully fabricated for the first time at 467nm with a champion EQE of 1.3% and a maximum brightness of 800cdm-2. This work gives insights into the luminescence mechanism of Sn-based perovskites and provides a new theoretical basis for the development of lead-free blue LEDs.

Synthesis of Sr6LuAl(BO3)6:Sm3+ Red Phosphor with Excellent Thermal Stability and Its Application in w-LEDs.

In this study, a series of Sr6LuAl(BO3)6:Sm3+ red phosphors were successfully prepared with a high-temperature solid-phase technology. The Rietveld refinement analysis of the X-ray diffraction (XRD) diffraction patterns indicated that the as-prepared phosphors belong to the R3¯ space group of the hexagonal crystal system. Under 404 nm near-ultraviolet excitation, the Sr6LuAl(BO3)6:Sm3+ phosphor exhibits narrowband emission within the range of 550 to 750 nm. The primary emission peak is observed at a wavelength of 599 nm, corresponding to 6H5/2 → 4F7/2. The optimum doping concentration of the Sr6LuAl(BO3)6:xSm3+ phosphor is 10 mol%. Nearest-neighbor ion interaction is the mechanism of concentration quenching. The synthesized phosphors demonstrate exceptional thermal stability, with a high quenching temperature (T0.5 > 480 K). Furthermore, the assembled white light-emitting diode (w-LED) device exhibits a low color temperature (5464 K), an excellent color rendering index (Ra = 95.6), and CIE coordinates (0.333, 0.336) close to those of standard white light. Collectively, these results suggest the enormous potential of Sr6LuAl(BO3)6:Sm3+ phosphors for applications in w-LEDs.

Inactivation of deposited bioaerosols on food contact surfaces with UV-C light emitting diode devices.

The airborne transmission of infectious diseases and bioaerosol-induced cross-contamination pose significant challenges in the food, dairy, and pharma industries. This study evaluated the effectiveness of 279 nm UV-C LED irradiation for decontaminating bioaerosols, specifically containing microorganisms such as Escherichia coli (C3040- Kanamycin resistant), Salmonella Enteritidis (ATCC 4931), and Pseudomonas fragi (ATCC 4973), on food contact surfaces. Borosilicate glass, silicon rubber, and stainless steel (316L) surfaces were selected for experimentation for their usage in the food industry. A 50 µL cell suspension was aerosolized at 25 psi pressure using a 4-jet BLAM Nebulizer within a customized glass chamber and then deposited onto the surface of the coupons. The serial dilution approach was used for the microbial enumeration, followed by duplicate plating. With a low Root Mean Square Error (RMSE) and high R2 values, the biphasic kinetic model for UV-C inactivation curves of all three pathogens demonstrated the excellent goodness of fit parameters. At a UV-C dose of 6 mJ cm-2, glass surfaces showed the maximum microbial inactivation (i.e., 2.80, 3.81, and 3.56 log CFU/mL for E. coli, Salmonella, and P. fragi, respectively). Stainless steel and silicon rubber surfaces showed significant microbial inactivation, but log10 reductions observed were consistently lower than glass surface. Our research indicates that UV-C LEDs (279 nm) can effectively disinfect bioaerosols on food contact surfaces.IMPORTANCEFood safety is a major public health concern, with contaminated food causing serious illnesses. UV-C light, used for germicidal action, is effective in disinfecting surfaces and is not subject to the same strict legal restrictions as chemical disinfectants, simplifying compliance with food safety regulations. In this study, we evaluated the efficacy of UV-C (279 nm) LED systems for inactivation of surface-deposited bioaerosols of kanamycin-resistant Escherichia coli (C3040), Salmonella Enteritidis (ATCC 4931), and Pseudomonas fragi (ATCC 4973). The research outcomes can be used to develop UV-based surface disinfection systems to minimize the risk of foodborne illnesses and enhance safety in high-traffic food preparation areas.

Ultrasonication synthesis of a Mn2+-doped zero-dimensional metal halide: Structure, luminescence property and display application

Metal halides have drawn attention owing to their unique optoelectronic properties. Since the toxicity of lead element is concerned, the design of lead-free metal halide materials is quite important. In this study, Mn2+-doped Cs2ZnBr4 microcrystals were successfully synthesized by a facile ultrasonication method. The structure, morphology, and luminescence properties were investigated in detail. When used as a green emitter, the white light-emitting diode (LED) device exhibits high performance with a wide color gamut of 115% NTSC. The relationship between the structure and luminescence performance was discussed. This study could provide new insight into the synthesis of metal halides and expand their potential in optoelectronic applications.

Atomic Layer Deposition of ZnO on CsPbBr3 Perovskite Nanocrystals: Surface-Dependent Mechanistic Insights.

In this study, we investigate the atomic layer deposition (ALD) process on all-inorganic CsPbBr3 perovskite nanocrystals (PNCs) to introduce an inorganic electron transport layer (ETL) in light-emitting diode (LED) devices. Two types of CsPbBr3 PNCs were synthesized with oleate (OA) and oleylammonium (OLA) ligands on the surface. We found that CsPbBr3 PNCs with Cs oleate surfaces experienced severe photoluminescence (PL) quenching after the ALD process, while those with oleylammonium bromide surfaces did not show any significant PL drop. Transmission electron microscopy and X-ray photoelectron spectroscopy revealed that significant Pb metal formation and Ruddlesden-Popper planar faults, linked to uncoordinated Pb2+ ion defects, were generated in CsPbBr3 PNCs terminated with Cs oleate after ALD ZnO. Finally, we fabricated LEDs using PNCs with an ALD ZnO process to introduce inorganic ZnMgO nanoparticles as the ETL. The devices processed with ALD exhibited superior luminance and external quantum efficiency compared to those without the ALD process. This research provides crucial insights into the surface-dependent chemistry of PNCs and the surface-dependent performance of perovskite-based optoelectronic devices.

Comparison of ZnO Nanoparticles Prepared by Spray Pyrolysis and Consecutive Method for UV-Driven Photocatalytic Degradation of Methylene Blue

ZnO is a semiconductor material that is widely used for many applications in industries such as solar cells, dye-sensitized solar cells, food packaging, photocatalytic, anti-microbial, light-emitting diode devices, and gas sensors. In this study, ZnO nanoparticles (NPs) have been successfully synthesized using two methods, namely spray pyrolysis and a consecutive method. The consecutive method is a combination of sol-gel and spray drying methods. The objective of this study is to investigate the photocatalytic performance of ZnO fabricated using those methods. Both methods used the same precursor, zinc acetate dehydrate as a source of zinc, but with different solvents and additives. Based on the X-ray diffraction pattern, the ZnO NPs synthesized using spray pyrolysis and a consecutive method exhibited similar polycrystalline hexagonal wurtzite structures. The large crystal sizes of ZnO NPs were obtained using a consecutive method, sol-gel followed by spray drying, in comparison with those from the ZnO spray pyrolysis. In contrast, the particle size of ZnO prepared by the consecutive method was in a smaller range. The SEM analysis implied that the ZnO structures had surface defects. In the UV-driven photocatalytic degradation of methylene blue, ZnO produced by the consecutive method exhibited slightly higher degradation performance than ZnO spray pyrolysis. This performance was attributed to the larger crystal size of ZnO NPs, which provided a longer carrier movement at semiconductor surfaces and reduced electron-hole recombination. Additionally, ZnO NPs produced using the consecutive method underwent agglomeration that leads to a smaller contact surface with methylene blue, obstructing the degradation process.

Antithermal-Quenching Near-Infrared Emitting Lu2SrAl4SiO12:Cr3+ Garnet-Type Phosphor for High-Resolution Nonvisual Imaging.

Near-infrared (NIR) light allows fast and nondestructive detection with deep penetration into biological tissues and is widely used in food inspection, biomedical imaging, night vision security, and other fields. Cr3+-doped NIR first region (NIR-I) phosphors have many interesting features that have attracted a lot of attention recently. However, practical issues, such as low photoluminescence quantum efficiency and poor thermal stability, need to be addressed. We synthesized Cr3+-doped Lu2SrAl4SiO12 garnet-type phosphors using a high-temperature solid-state reaction method. Under blue-light (@ 430 nm) excitation, the phosphors exhibited broadband NIR-I emission in the range of 600-1000 nm, with an emission peak at 710 nm. This system is unique, as the emission had multipeak sharp-line superposition and the Cr3+ ions were situated in a relatively strong crystal field environment, as opposed to a weak crystal field environment for other matrix. The optimal doping content of Cr3+ ions was 2 mol %, and its internal quantum efficiency was ∼76.8%. Surprisingly, this NIR phosphor showed an antithermal quenching effect, and the integrated luminescence intensity of NIR-I emission measured at 573 K was 206.3% of that measured at 303 K. We found that the antithermal quenching of NIR-I luminescence was caused by the extremely low thermal expansion coefficient and rigid structure of the Lu2SrAl4SiO12 matrix in the temperature range, as well as the weakening of electron-phonon coupling with increasing temperature. The optimized phosphor was packaged with a blue chip into a NIR phosphor-converted light-emitting diode device. The light source device showed an output power of 119.02 mW and an electro-optical conversion efficiency of 11.02% under a driving current of 300 mA. The application potential of this NIR phosphor was demonstrated in the field of high-resolution nondestructive imaging.

Enhanced Emission in Polyelectrolyte Assemblies for the Development of Artificial Light-Harvesting Systems and Color-Tunable LED Device.

Artificial light-harvesting systems (LHSs) are of growing interest for their potential in energy capture and conversion, but achieving efficient fluorescence in aqueous environments remains challenging. In this study, a novel tetraphenylethylene (TPE) derivative, TPEN, is synthesized and co-assembled with poly(sodium 4-styrenesulfonate) (PSS) to enhance its fluorescence via electrostatic interactions. The resulting PSS⊃TPEN network significantly increased blue emission, which is further harnessed by an energy-matched dye, 4,7-di(2-thienyl)benzo[2,1,3]thiadiazole (DBT), to produce an efficient LHS with yellow emission. Moreover, this system is successfully applied to develop color-tunable light-emitting diode (LED) devices. The findings demonstrate a cost-effective and environmentally friendly approach to designing tunable luminescent materials, with promising potential for future advancements in energy-efficient lighting technologies.

Progress, application and prospect of rare earth-based perovskite light-emitting diodes

Perovskites recently become star materials in light-emitting diodes (LEDs) field due to their high color purity, tunable emission spectra, and cost-effectiveness. However, the commercial applications of perovskite LEDs are hampered by inferior lattice stability of perovskite materials. Successful modification of functional materials is a promising strategy towards efficient and stable perovskite LEDs. Rare earth (RE) metals are incorporated into the perovskite lattice, including double perovskites, by occupying the B-site or A-site in perovskite such as ABX3 or A2BB'X6, forming the RE-based perovskite. Doping with RE ions enables precise control emission color of materials across a broad spectrum ranging from ultraviolet to near infrared. Moreover, this strategy reduces the energy loss in electron relaxation process and enhances electroluminescence intensity of LED device, thereby improving the potential of commercial applications of perovskite LEDs. This review provides a comprehensive and systematic summarization of recent progress and challenges in RE-based perovskite materials (structure types, luminescence mechanism and synthesis methods) and LEDs (device structures and main applications) to provide some enlightening insights for realization of efficient and stable RE-based perovskite LEDs.

Light-induced synthesis of highly stable CsPbCl3:Mn2+@mSiO2 nanocomposites for white Light-Emitting Diodes

All-inorganic perovskite nanocrystals (NCs) exhibit great promise in optoelectronics and photovoltaics. However, their intrinsic low-thermal/oxygen/moisture stability and the rigorous synthesis procedures have limited the practical applications. Here, we present a facile, one-step, light-induced method to synthesize CsPbCl3:Mn2+ NCs at room temperature by using carbon tetrachloride (CCl4) as the halide source. The corresponding formation mechanism of CsPbCl3:Mn2+ NCs is revealed, where CsPbCl3:Mn2+ NCs are formed through the direct incorporation of [MnCl6]4− octahedral into the perovskite lattice during the nucleation and growth process. Additionally, we demonstrate the in-situ growth of CsPbCl3:Mn2+ NCs within mesoporous silica (mSiO2) spheres to form CsPbCl3:Mn2+@mSiO2 nanocomposites via the light-induced method, resulting in a remarkable improvement in high-temperature and long-time stability. As a prototype experiment, a white light-emitting diode (WLED) device is constructed using CsPbCl3:Mn2+@mSiO2 nanocomposites, which exhibits a bright white-light emission with the CIE chromaticity coordinate of (0.352, 0.340). It is anticipated that light-induced synthesis method provides a straightforward strategy for synthesizing multifunctional halide perovskite nanocrystals and nanocomposites for versatile applications.

Red light-emitting diode with full InGaN structure on a ScAlMgO4 substrate

Abstract Here, we report the first demonstration of a full InGaN-based red LED grown on a c-plane ScAlMgO4 substrate. This work represents a potential approach for achieving red emissions from an InGaN quantum well grown on InGaN underlying layers. The LED device exhibits a peak wavelength of 617 nm at a current injection of 40 mA (10.5 A cm−2). The light output power and external quantum efficiency were 12.6 μW and 0.016% at 40 mA (10.5 A cm−2), respectively. These results are expected to contribute to the development of longer-wavelength emission LEDs and laser diodes.

Anion regulation for surface passivation enables ultrahigh-stability perovskite nanocrystals.

All-inorganic perovskite CsPbBr3 nanocrystals (NCs) display high photoluminescence quantum yield and narrow emission, which show great potential application in optoelectronic devices. However, the poor environment stability of NCs will hinder their practical application. Herein, a series of ionic liquids with different anions (BF4-, Br-, and NO3-) were used as a sole capping ligand to synthesize NCs. Among the three samples, 1-hexadecyl-3-methylimidazolium tetrafluoroborate ([C16MIM]BF4) capped NCs have the highest stability in light, thermal, and water, possibly attributing to the in situ passivation of bromine vacancy via pseudohalogen BF4- and tight binding of ionic liquid ligands and lead atoms. In addition, green-emission [C16MIM]BF4 NCs were used to assemble a white light-emitting diode device, and it possessed a wide National Television System Committee color gamut of 124.5% and a stable emission peak at high driving currents of 380 mA. This work paves the way for resurfacing perovskite NCs with ultrahigh stability, thereby driving the perovskite NC display industry closer to real-world application.

Structure regulation and luminescence improvement of Gd3Ga5O12:Cr3+: An anti-thermal quenching NIR phosphor for multifunctional applications

Near-infrared (NIR) phosphors converted light emitting diodes (LEDs) are booming as next NIR light sources. But the quantum efficiency and thermal stability of the NIR phosphors need to be improved. Here, thermally stable garnet Gd3Ga5O12 is selected as the matrix and Cr3+ as the luminescent center to obtain Gd3Ga5O12:Cr3+ NIR phosphor. Equivalent smaller Lu3+ was adopted to regulate the structure of Gd3Ga5O12 to further improve the luminescence performance. By regulating the structure the emission spectra shift toward blue region and the intensity is improved. Optimized GdLu2Ga5O12:Cr3+ exhibits anti-thermal quenching behavior and the internal quantum efficiency reaches 73.69 %. Relative sensitivity value of the phosphor GdLu2Ga5O12:Cr3+ reaches 3.353 % K−1 at 423 K based on lifetime mode. LED device is fabricated by combining the phosphor GdLu2Ga5O12:Cr3+ and the commercial red phosphor with blue chip. Electroluminescence spectrum can cover the absorption spectra of the plant dyes well. The lettuce grow faster by adopting this LED device as compensating light source. This work provides an anti-thermal quenching NIR phosphor for multiple applications.

High color rendering index WLEDs enabled by multi-band tuning of InP quantum dots

Quantum dots (QDs) represent a significant class of fluorescent materials, offering the potential to reduce power consumption and enhance the color rendering index (CRI) of white light-emitting diode (WLED) devices. However, the presence of toxic elements such as Cd and Pb in traditional fluorescent QDs limits their widespread commercial application. Compared to the broad emission characteristics of environmentally friendly AgInS2 and CuInS2 QDs, the narrower linewidth of InP-based core-shell QDs is advantageous for developing WLED devices with a higher CRI. In this study, we employed a multistage heating method to synthesize a series of amino-phosphine-based InP/ZnSe core-shell QDs, which exhibited emission wavelengths ranging from 535 to 650 nm, narrow emission linewidths of 43-47 nm, and high photoluminescence quantum yields of 60%-80%. Subsequently, six different color QDs are used to fabricate a WLED device. The best WLEDs show not only bright warm light (correlated color temperature = 3323 K) with a maximum luminous efficacy of 74.1 lm W-1, but also excellent color quality (CRI Ra = 93, as well as R9 = 94.8, and R13 = 97.1). These results indicate remarkable progress in InP-based WLEDs for high-quality lighting applications.

Spectral characteristics and luminescence applications of Eu3+-activated fluorosilicate Na2MgGd2[SiO3]4F2

This work reports the luminescence spectra and application of novel Eu3+-doped Na2MgGd2[SiO3]4F2 phosphor. The X-ray powder diffraction confirmed the pure phase formation of the samples with the monoclinic space group P21/c (No:14). The phosphors demonstrated efficient red emission at 613 nm from the electric dipole transitions 5D0→7F2. The optimal doping concentration was found to be approximately 25 mol%. Na2MgGd2[SiO3]4F2:0.25Eu3+ exhibits a high quantum efficiency (QE) of 57 % with excellent thermal stability and pure chromaticity. Red- and the white light-emitting diode devices were packaged using InGaN chips and Na2MgGd2[SiO3]4F2:0.25Eu3+. The fabricated WLED has CIE coordinates of (x = 0.33, y = 0.34), which are very close to the white point in the National Television System Committee (x = 0.33, y = 0.33). The color rendering index (CRI, Ra) and correlated color temperature (CCT) of the WLED are 91 and 4400 K, respectively. The results show that as a red luminescent phosphor, it is a potential candidate for the preparation of near-UV/blue InGaN-based WLEDs.