Blue Chip Research Articles

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.

Enhancement strategy of thermal stability and photoluminescent intensity of Cr3+ doped Li3+xZn2–2xGaxSbO6 phosphor in a strong crystal field

Near-infrared phosphor-converted light-emitting diodes (pc-LEDs) have shown enormous influence in various applications such as night vision, non-destructive detection，especially in the realm of plant cultivation. However, the role of phosphors presently employed in plant cultivation is typically limited, serving primarily for the purpose of illumination. In this work, a series of near-infrared phosphors Li3+xZn2–2xGaxSbO6: 0.02Cr3+(LZGS: 0.02Cr3+) under 450 nm excitation was successfully synthesized by high-temperature solid-state method. Through precise modulation of Ga3+ ions, a blue shift in the emission spectrum was observed, demonstrating excellent overlap with the absorption spectrum of Phytochrome. To explain two phenomena of spectral blue shift and the enhancement in luminescence intensity, density functional theory calculations have been performed. Additionally, a crystal field strength Dq/B of 3.48 was achieved, which represents the highest value currently reported for Cr3+-doped phosphors. The results offer potential applications of LZGS: 0.02Cr3+ in temperature sensing, enabling precise detection of the environmental temperature for plant growth. Finally, pc-LED devices were made by combining LZGS: 0.02Cr3+ with 450 nm blue light chips and applied to plant lighting, temperature measurement, and anti-counterfeiting, demonstrating the potential of LZGS: 0.02Cr3+ in multifaceted applications.

PMMA-Au@YAG:Ce phosphor deposited on flexible substrate for white light emitting devices

This paper investigates the possibility to obtain yttrium aluminum garnet doped with cerium ions (YAG:Ce) phosphor, improve the emissive properties by modification with metal nanoparticles, followed by embedding into the polymer matrix, and deposition of nanocomposite on a flexible substrate to produce the white light by excitation with a blue chip. YAG:Ce yellow phosphor was obtained by a modified solid-state process, followed by in-situ anchoring of gold nanoparticles (Au@YAG). To deposit the phosphor on the flexible substrate, the Au@YAG nanocomposite was embedded in a poly(methyl methacrylate) (PMMA) matrix using the ex-situ method. The quality of the phosphor particles and composites was studied using FTIR spectroscopy, X-ray diffraction, and fluorescence spectroscopy. The applicability of the developed materials and the efficiency of methods were confirmed by the photometric studies performed on the composite film to determine the chromaticity coordinates, leading to the parameters of the semiconductor device that generates cold white light.

A novel red-emitting InScW3O12:Eu3+ phosphor with anti-thermal-quenching performance for high-power WLED applications

A series of red-emitting InScW3O12:Eu3+ (ISWO:Eu3+) phosphors with anti-thermal-quenching performance were successfully synthesized by conventional solid-state reaction. The phase structure and luminescent properties of ISWO:Eu3+ were systematically studied. The photoluminescence excitation (PLE) spectrum showed that ISWO:Eu3+ phosphor can be effectively matched with commercial ultraviolet (UV), violet and blue light chips. The main emission peak of the phosphor was located at 613 nm, which was attributed to the electric dipole transition 5D0 → 7F2. Under the optimal excitation, the prepared ISWO:0.08Eu3+ phosphor showed excellent anti-thermal-quenching performance, its photoluminescence (PL) intensity at 180 °C reached 157.4 % of initial intensity at room temperature. At 465 nm excitation, it also exhibited the anti-thermal-quenching property and the PL intensity remained 115.1 % at 150 °C of that at room temperature. In situ XRD analysis revealed that the lattice contraction resulting in an increase in structural rigidity as the temperature rising, which caused the change of Eu3+ local environment and improved the PL intensity. Finally, a series of warm white LED devices under varying power density conditions with stable output were prepared using the red ISWO:0.08Eu3+ phosphor, indicating that the ISWO:Eu3+ phosphor with excellent anti-thermal-quenching performance has potential application prospects in high-power white light-emitting diodes (WLEDs).

Asset pricing in African frontier equity markets

This paper undertakes a horse races style comparison of the efficacy of a range of multifactor asset pricing models in explaining the cross section of stock returns in African securities markets. Valuation factors used include size, book-to-market value, momentum, operating profit, asset growth or investment, liquidity and investor protection. Using monthly returns of 375 blue chip firms from 8 African equity markets over 23 years, we undertake a horse-race style comparison of various classes of augmented CAPM models. We show that both the Fama & French (2015) five factor and Fama & French (2018) six factor framework yield the highest explanatory power. Analysis of costs of equity and optimized portfolio opportunity set simulations reveal substantial differences arising and borne by practitioners from the contrasting application of different asset pricing models underscoring the timely importance of our study.

Mn2+ doped aluminum-rich spinel transparent ceramic phosphor with higher performance for wide color-gamut backlight display

Due to the great potential of narrow-band green-emitting phosphors for wide color-gamut white light-emitting diodes (WLED) backlight displays, there is great interest in finding host materials with the desired luminescent properties and high quantum efficiency. Herein, a series of Mg0.98-xAl2(1+x/3)O4: 0.02Mn2+ (x = 0, 0.125, 0.25) powders were synthesized using high-temperature solid-phase reactions, followed by a combination of pressureless sintering and hot isostatic pressure sintering to fabricate transparent ceramic phosphors. The crystal structure refinement, NMR spectroscopy, and photoluminescence results show tetrahedral coordination of Mn2+ ions and an increase in cation vacancies and disorder with increasing x. These transparent ceramics exhibit narrow-band green emission, which shifts from 523 to 520 nm with increasing x. The Mg0.855Al2.08O4: 0.02Mn2+ ceramic sample has an in-line transmittance of over 80 % above 500 nm and internal quantum efficiencies as high as 96.2 %. The luminous intensity of the Mg0.855Al2.08O4: 0.02Mn2+ ceramic remains above 88.6 % at 425 K compared to room temperature, with a thermal conductivity of 12.4 W·m−1·K−1. A WLED device fabricated using the Mg0.855Al2.08O4: 0.02Mn2+ ceramic, K2SiF6:Mn4+ phosphors, and a blue chip show a wide color gamut of 126 % National Television System Committee standard. The results show that Mn2+-doped aluminum-rich spinel transparent ceramics have great potential for application in wide color gamut WLED backlight devices.

Novel narrowband emitting red phosphor Sr3La2W2O12:Eu3+ with excellent thermal stability for WLEDs

AbstractThe development of red phosphors with good thermal stability, high quantum yield and high color purity is still a big challenge. In this work, a series of novel red phosphors Sr3La2W2O12:xEu3+ (0≤x≤0.18, ∆x = 0.03) were successfully prepared by high‐temperature solid‐phase method. The phosphors reveal a hexagonal phase with the space group of R‐3 m. The phosphor Sr3La2W2O12:Eu3+ produced narrowband red emission from 5D0→7F2 of Eu3+ (616 nm) under excitation at 395 nm, 465 nm, and 533 nm. Importantly, phosphor Sr3La2W2O12:0.09Eu3+ exhibits astonishing quantum efficiency (IQE = 89.60%, EQE = 41.52%), and it demonstrate robust thermal performance with the emission intensity retaining 92.73% at 558 K of that at 298 K. Finally, the prepared red phosphor Sr3La2W2O12:0.09Eu3+ and yellow phosphor YAG:Ce3+ were combined with a blue LED chip (460 nm) to form a WLED device, which presented warm white light with color coordinates of (0.3523, 0.3732), color rendering index of 83.7, and color temperature of 4826 K.

Full-Visible-Spectrum White LEDs Enabled by a Blue-Light-Excitable Cyan Phosphor.

Efficient blue-light-excitable broadband cyan-emitting phosphors may yield full-visible-spectrum white light-emitting diodes (WLEDs) with ultrahigh color rendering (Ra > 95). However, this requires closing the "cyan gap" in the 480-520 nm region of the visible spectrum, which is challenging. Herein, a well-performed cyan-emitting garnet phosphor Ca2LuAlGa2Si2O12:Ce3+ (CLAGSO:Ce3+) is reported. Under 430 nm excitation, the optimal CLAGSO:5%Ce3+ compound exhibits a broadband cyan emission (peak, 496 nm; bandwidth, 102 nm) with a high internal quantum efficiency of 85.6% and an excellent thermal resistance performance (69.1% at 423 K). Importantly, this as-prepared cyan-emitting phosphor provides sufficient cyan emission and enables filling the well-known so-called "cyan gap" between the blue LED chip and the commercial Y3Al5O12:Ce3+ (YAG:Ce3+) yellow phosphor. Impressively, a WLED device fabricated with the optimal CLAGSO:5%Ce3+ sample shows a low correlated color temperature (4053 K) and an ultrahigh color rendering index (Ra = 96.6), as well as an excellent luminous efficacy (74.09 lm W-1). These results highlight the importance of blue-excited broadband cyan-emitting phosphors in closing the cyan gap and enabling human-centric full-visible-spectrum warm WLED devices for high-quality solid-state lighting.

Highly efficient red emission of CsPbBrI2 quantum dots glasses modified by Nb5+ for light-emitting application

Red-emitting perovskite quantum dots (QDs) have significant potential for application in optoelectronic devices. However, their application is hindered by preparation challenges and low photoluminescence quantum yield (PLQY). In this study, CsPbBrI2 red-emitting QDs with a PLQY of up to 58.73 % were synthesized in germanium borate glass. The experimental results indicated that the addition of Nb5+ can not only partially replace the Pb2+ sites but also passivate halogen defects in QDs, enhance radiative transitions, and significantly improve the lattice ordering of CsPbBrI2 QDs glass. Additionally, the incorporation of Nb2O5 supplies free oxygen, facilitating the conversion of [BO4] to [BO3] in the glass network, which results in a looser structure conducive to crystallization. Moreover, the Nb5+-doped CsPbBrI2 QDs glass demonstrated excellent hydrothermal stability. The QDs glass exhibiting the highest luminescent performance was subsequently combined with an InGaN blue chip to create a WLED with a color rendering index (CRI) of 82.7. This study offers an innovative methodology for synthesizing perovskite QDs glass materials with enhanced red emission efficiency through transition metal doping, highlighting their significant potential for practical applications in WLEDs.

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.

Crystallization and luminescence properties of stable CsPbBr3 Nanocrystals in Li2B4O7 glass

All-inorganic CsPbX3 (X = Cl, Br, and I) perovskite nanocrystals (NCs), have achieved unprecedented advances in opto-electronic applications. However, issues such as poor stability and the volatility of halides in the preparation process continue to hinder their practical applications. Here, lithium tetraborate (Li2B4O7) was chosen as the glass matrix to prepare CsPbBr3 NCs glasses through traditional melting-quenching and heat treatment processes, effectively reducing the glass synthesis temperature to 940 °C. The heat treatment temperature and duration are examined. The Li2B4O7 glass matrix exhibits a uniform structure and high transmittance and CsPbBr3 NCs precipitated uniformly after heat treatment. Among these glasses, the sample heat-treated at 510 °C for 5 h exhibited an optimal photoluminescence quantum yield of 76.1 % and the narrowest full width at half maximum values of 24 nm. Its photoluminescence intensity maintained 96.6 % of its original value after multiple thermal cycles and thermal shocks, demonstrating the sample's robust thermal stability. Finally, by integrating the CsPbBr3 NCs glass sample with a blue chip in simple device packaging, a green light-emitting diode was successfully fabricated, featuring excellent luminescence stability and a color purity of up to 96.4 %, promising for applications in solid-state lighting and display technologies.

Bright Structural-Phase-Pure CsPbI3 Core-PbSO4 Shell Nanoplatelets With Ultra-Narrow Emission Bandwidth of 77 meV at 630 nm.

Achieving a narrow emission bandwidth islong pursued for display applications. Among all primary colors, obtaining pure red emission with high visual perception is the most challenging. In this work, CsPbI3 halide perovskite nanoplatelets (NPLs) with rigorously controlled 2D [PbI6]4- octahedron layer number (n) are demonstrated. A perovskite core-PbSO4 shell structure is designed to prevent aggregation and fusion between NPLs, enabling consistent thickness and quantum confinement strength for each NPL. Consequently, exact n = 4 CsPbI3NPLs are demonstrated, exhibiting emission peaks around 630nm, with very narrow spectral bandwidths of <24nm and high absolute photoluminescence quantum yields up to 85%. The emission of n = 4 NPLs falls exactly within the pure-red region, closely aligning with the International Telecommunication Union Recommendation BT.2020 standard. Measurements suggest predominant stability and color homogeneity compared to traditional red-emitting CsPbIxBr3- x nanocrystals. Finally, proof-of-concept pure-red emissive light-emitting diodes (LEDs) are demonstrated by integrating n = 4 CsPbI3 NPLs films with a blue LED chip, showing an excellent external quantum efficiency of 18.3% and high brightness exceeding 3 × 106 nits. Stringent requirements for future display technologies, are satisfied based on the high color purity, stability, and brightness of CsPbI3 NPLs.

Surface Vibration‐Mediated and Multiphonon Relaxation‐Assisted Antithermal‐Quenching Shortwave Infrared Emission in Ho‐Based Double Perovskite With Long Lifetime

AbstractThermal quenching generally predominates in Er3+ 1540 nm luminescence quenching at elevated temperatures, due to intensified lattice vibration and efficient overtone vibrational relaxation by O─H stretch. This issue impedes practical device applications of shortwave infrared Er‐doped phosphors. Herein, with the mediation of surface vibrational phonons, anti‐thermal quenching of Er3+ 1540 nm emission is reported in (220)‐dominated Er3+‐doped Cs2NaHoCl6 double perovskite. The downshifting emissions can be boosted with rising temperatures from 303 to 543 K, reaching 225%@483 K of the initial intensity at 303 K, accompanied with a long lifetime of 33.02 ms at 483 K. By combining temperature‐dependent in situ Raman and Fourier transform infrared spectroscopies with the excited‐state dynamics results, the coordination role of water molecules is verified, serving as promoters instead of quenchers on the (220) facet at high temperatures. Furthermore, efficient energy transfer from Ho3+ to Er3+ enables intense 1540 nm emission with a photoluminescence quantum yield of 78.1% under 450 nm excitation. Finally, a compact thermally stable phosphor‐converted light‐emitting diode (LED) is designed as a narrowband shortwave infrared light source with a blue LED chip. This work pushes the improved understanding of achieving thermal‐enhanced Er3+ luminescence for potential broad applications.

Efficient Broadband Near‐Infrared Emitters in Lead‐Free Metal Halides with Record Photoluminescence Quantum Yield Under Blue Light Excitation

AbstractRealizing ultra‐efficient broadband near‐infrared (NIR) luminescence, especially under blue light excitation, remains an enormous challenge in lead‐free metal halides. Herein, the efficient NIR emission under blue light excitation is achieved in Sb3+‐doped 0D (ETPP)2ZnCl4xBr4‐4x (x = 0–1) (ETPP+ = (Ethyl)triphenylphosphonium) through coordination structure modulation and halogen substitution. Compared with the visible light emission of Sb(III)‐based compounds, the emission in Sb3+‐doped (ETPP)2ZnCl4xBr4‐4x shifts to the NIR region due to the large excited state lattice distortion. Parallelly, the excitation bands gradually shift from 376 to 450 nm as Br gradually replaces Cl, and the emission bands can further shift from 702 to 763 nm. Thus, the broadband NIR emission at 763 nm with a record luminous efficiency of 55.4% under 450 nm excitation can be achieved in Sb3+‐doped compounds. Moreover, the large‐scale synthesis technique of Sb3+‐doped (ETPP)2ZnBr4: NIR phosphors at room temperature is further developed and this compound exhibits impressive thermal and chemical‐stabilities. Finally, a high‐performance NIR light‐emitting‐diode is fabricated by combining a commercial blue chip and (ETPP)2ZnBr4:10%Sb3+ phosphors, which shows the most advanced photoelectric efficiency (17.8%) and output power (67.7 mW) in lead‐free metal halides. Thus, the as‐fabricated device is further demonstrated in the applications of night vision and biomedical imaging.

Efficient and Near-Zero Thermal Quenching Cr3+-Doped Garnet-Type Phosphor for High-Performance Near-Infrared Light-Emitting Diode Applications.

In recent years, near-infrared (NIR) phosphors have attracted great research interest due to their unique physical properties and broad application prospects. However, obtaining NIR phosphors with both high quantum efficiency and excellent thermal stability remains a great challenge. In this study, novel NIR Ca3Mg2ZrGe3O12:Cr3+ phosphors were successfully prepared using a high-temperature solid-phase method, and the structure and luminescent properties of the material were systematically investigated. Ca3Mg2ZrGe3O12:0.01Cr3+ emits NIR light in the range of 600 to 900 nm with a peak at 758 nm and a half-height width of 89 nm under the excitation of 457 nm blue light. NIR luminescence shows considerable quantum efficiency, and the internal quantum efficiency of the optimized sample is up to 68.7%. Remarkably, the Ca3Mg2ZrGe3O12:0.01Cr3+ phosphor exhibits a near-zero thermal quenching behavior, and the luminescence intensity of the sample at 250 °C maintains 92% of its intensity at room temperature. The mechanism of high thermal stability has been elucidated by calculating the Huang Kun factor and activation energy. Finally, NIR pc-LED devices prepared from Ca3Mg2ZrGe3O12:0.01Cr3+ phosphor with commercial blue LED chips have good performance, proving that this Ca3Mg2ZrGe3O12:0.01Cr3+ NIR phosphor has potential applications in night vision and biomedical imaging.

La3Sc2Ga3O12:Cr3+, Nd3+ near-infrared phosphor for nondestructive detection and luminescence thermometry

To develop continuous broadband emission near-infrared (NIR) phosphors compatible with blue LED chips, numerous Cr3+-Yb3+ co-doped phosphors have been synthesized. However, the emission spectra of Cr3+ vary significantly across different matrix materials, while Yb3+ maintains a relatively stable emission spectrum. This variation leads to notable luminescence depressions between 850 and 900 nm in many Cr3+-Yb3+ co-doped phosphors. To address this emission spectrum gap, we utilized Cr3+ as a sensitizer and introduced Nd3+ as the luminescence center within the La3Sc2Ga3O12 matrix material, establishing a Cr3+-Nd3+ energy transfer channel. Under 480 nm excitation, we tuned emission peaks at 800 nm (Cr3+) and 881 nm (Nd3+). The stable NIR emission of Nd3+ effectively compensates for the missing spectrum in Cr3+-Yb3+ co-doping. The Cr3+-Nd3+ energy transfer process was thoroughly analyzed using diffuse reflection spectrum, excitation spectrum, and fluorescence decay curves. The LSGO:0.125Cr3+, 0.03Nd3+ compound with the best optical performance was packaged with a 480 nm LED chip to create a NIR light source. At a working current of 10 mA, it achieved a photoelectric conversion efficiency of 9.45 %, demonstrating its potential for applications in non-destructive detection and luminescence thermometry. This work presents a novel strategy for tuning NIR spectral distribution and developing continuous broadband NIR phosphors.

Activator Heavy Solid Solution in Rigid Framework: An Effective Strategy Toward Highly Efficient and Thermally Stable Near‐Infrared Emission for Wireless Communication

AbstractBroadband near‐infrared (NIR) phosphors are crucial components of next‐generation NIR lighting sources. However, the design of high‐efficiency and thermally stable NIR phosphors still poses a significant challenge, whose quantum efficiencies (QEs) are directly limited by their absorption efficiency (AE) toward incident light. Here, an efficient and thermally stable NIR emission with AE up to 64.9% and emission keeping of 91.23% at 423 K is demonstrated via Cr3+ heavy solid solution in rigid framework LiCaGaF6:Cr3+ (LCGFC). Isomorphic LiCaAlF6:Cr3+ also exhibits thermal robustness, while traps in low doping concentration and low QEs. Comparative studies on crystal structure, formation energy, and Helmholtz free energy disclose that Cr3+ substitution on equivalent and equiradius Ga3+ site versus radii differential Al3+ site generates heavier solid solution and sustainable structural rigidity with acquirement of higher AE and better thermal stability. Incorporating LCGFC with a blue InGaN chip, a NIR phosphor‐converted light‐emitting diode is fabricated to realize stable wireless optical communication with good penetrability through biological tissue and some organic products. These findings develop a strategy based on activator heavy solid solutions in a rigid framework to achieve high‐efficiency and thermally stable NIR phosphors but also advance their novel optoelectronic applications.

A phosphor-in-glass film prepared with a novel orange Lu2GdMg2AlSi2O12:Ce3+ phosphor and a cyan BaSi2O2N2:Eu2+ phosphor

The preparation of phosphor-in-glass (PiG) films containing orange and cyan phosphors is one of the possible ways to improve the color rendering index (CRI) and correlated color temperature (CCT) of white LEDs packaged with PiG films. Recently, by matrix ion substitution, we have synthesized a novel orange Lu2GdMg2AlSi2O12:Ce3+ phosphor. Then, we used a “coating and low-temperature sintering” method to prepare PiG films containing this novel orange phosphor and the commercial cyan BaSi2O2N2:Eu2+ phosphor on sapphire substrates. Combining these PiG films with blue LED chips, warm white LEDs with CRI above 90 and CCT below 4000 K can be obtained. This suggests that the PiG films containing cyan and orange phosphors are promising to improve the CCT and CRI of white LEDs packaged with PiG films.

Analisis Suku Bunga, Kurs dan Inflasi terhadap Return Saham Blue Chip Sektor Perbankan

This study aims to analyze the factors that influence stock returns, especially blue chip stocks in the banking sector. The variables used in this study are interest rates, exchange rates and inflation. This research uses a quantitative approach with multiple linear regression analysis models. The results showed that the variable interest rates, exchange rates and inflation affect the blue chip stock returns of the banking sector. But partially, interest rates do not affect the blue chip stock returns of the banking sector while the exchange rate and inflation affect the blue chip stock returns of the banking sector. This research is very useful for investors in making investment decisions, especially in the banking sector.

High-Performance Tunable Near-Infrared Emitters of Cr3+-Activated Garnet Phosphor Enabled by Chemical Unit Co-Substitution.

The escalating demand for portable near-infrared (NIR) light sources has posed a formidable challenge to the development of NIR phosphors characterized by high efficiency and exceptional thermal stability. Taking inspiration from the chemical unit co-substitution strategy, high-performance tunable (Lu3- xCax)(Ga5- xGex)O12:6%Cr3+ (x = 0-3) phosphors are designed with an emission center from 704 to 780nm and a broadest full width at half maximum (FWHM) of up to 172nm by introducing Ca2+ and Ge4+ ions into the garnet structure. In particular, Lu3Ga5O12:6%Cr3+ demonstrates an anti-thermal quenching phenomenon (I423K = 113.1%). Compared to Lu3Ga5O12:6%Cr3+, Lu2CaGa4GeO12:6%Cr3+ exhibits significantly improved FWHM and IQE by 108nm and 25.5%, respectively, while maintaining good thermal stability (I423K = 80.4%). Finally, Lu2CaGa4GeO12:6%Cr3+ phosphor is combined with a 465nm blue LED chip to fabricate NIR LED devices, exhibiting a NIR electroluminescence efficiency of 13.31%@100mA and demonstrating successful applications in nocturnal illumination and biomedical imaging technology. This work offers a fresh perspective on the design of highly efficient NIR garnet phosphors.