Broadband near-infrared (NIR) emitting materials are in great demand as next-generation smart NIR light sources. In this work, a Cr3+-substituted phosphor capable of efficiently converting visible to NIR light is developed through the solid solution, Ga2–x In x O3:Cr3+ (0 ≤ x ≤ 0.5). The compounds were prepared using high-temperature solid-state synthesis, and the crystal and electronic structure, morphology, site preference, and photoluminescence properties are studied. The photoluminescence results demonstrate a high quantum yield (88%) and impressive absorption efficiency (50%) when x = 0.4. The NIR emission is tunable across a wide range (713–820 nm) depending on the value of x. Moreover, fabricating a prototype of a phosphor-converted NIR light-emitting diode (LED) device using 450 nm LED and the [(Ga1.57Cr0.03)­In0.4]­O3 phosphor showed an output power that reached 40.4 mW with a photoelectric conversion efficiency of 25% driven by a current of 60 mA, while the resulting device was able to identify damaged produce that was undetectable using visible light. These results demonstrate the outstanding potential of this phosphor for NIR LED imaging applications.

Broad-band near-infrared (NIR) phosphors are essential to assembling portable NIR light sources for applications in spectroscopy technology. However, developing inexpensive, efficient, and thermally stable broad-band NIR phosphors remains a significant challenge. In this work, a phosphate, KAlP2O7, with a wide band gap and suitable electronic environment for Cr3+ equivalent substitution was selected as the host material. The synthesized KAlP2O7:Cr3+ material exhibits a broad-band emission covering 650–1100 nm with a peak centered at 790 nm and a full width at half-maximum (fwhm) of 120 nm under 450 nm excitation. The internal quantum efficiency (IQE) was determined to be 78.9%, and the emission intensity at 423 K still maintains 77% of that at room temperature, implying the high efficiency and excellent thermal stability of this material. Finally, a NIR phosphor-converted light-emitting diode (pc-LED) device was fabricated by using the as-prepared material combined with a 450 nm blue LED chip, which presents a high NIR output power of 32.1 mW and excellent photoelectric conversion efficiency of 11.4% under a drive current of 100 mA. Thus, this work not only provides an inexpensive broad-band NIR material with high performance for applications in NIR pc-LEDs but also highlights some strategies to explore this class of materials.

the medical diagnostic fields than ever before. [1][2][3][4] There is a particular focus on materials operating in the 700-1100 nm region of the electromagnetic spectrum because this range covers the characteristic absorption signals of the CH, OH, and NH normal modes. Analyzing these vibrations enables the quick and nondestructive detection of biomolecules, including sugar, protein, fat, or the presence of harmful ingredients like pesticide residues. [5,6] Moreover, the NIR light in this energy region is known as the first biological window. It allows an appreciable penetration depth in biological tissues, making the NIR light suitable for radioisotope-free tissue imaging and noninvasive blood glucose sensing, among other uses. [7] Finally, NIR light can be detected by inexpensive silicon-based detectors, making sensors based on these wavelengths cost-effective and easily deployed. [8] The biggest challenge inhibiting the further deployment of this technology today is the limited capability to efficiently generate broadband NIR light. [9] Phosphor-converted NIR light-emitting diodes (pc-NIR LEDs) have been recently demonstrated to be the superior option for NIR production because of their outstanding output power, efficiency, durability, and compact size over other more traditional NIR light sources, including incandescent bulbs, tungsten halogen lamps, or even NIR LEDs. [10,11] These advantages make pc-NIR LEDs ideal for accessible, lowcost spectroscopic applications. However, these devices require efficient and thermally stable phosphors to convert the nearly monochromatic blue emission from commercially available InGaN chips into the requisite broadband NIR light.Generally, broadband NIR phosphors can be created by introducing an activator ion, like Eu 2+ , Bi 2+ , Mn 2+ , or Cr 3+ into an inorganic solid-state host compound. [12] Of the options available, Cr 3+ in a weak crystal field environment, with its unique 3d 3 electronic configuration, is considered the best option for broadband NIR emission. [13,14] Cr 3+ can be excited by blue light and emits between 700 and 1100 nm. This concept has led to the discovery of numerous Cr 3+ -substituted NIR phosphors. For example, garnets like Gd 3 Sc 2 Ga 3 O 12 :Cr 3+ (full width at half maximum (fwhm) = 110 nm, λ em = 756 nm) and Ca 3 Sc 2 Si 3 O 12 :Cr 3+ (fwhm = 92 nm, λ em = 783 nm) were both reported to have a quantum yield (QY) surpassing 90% and low thermal quenching, which is defined by the drop in emission Efficient broadband near-infrared (NIR) emitting materials with an emission peak centered above 830 nm are crucial for smart NIR spectroscopy-based technologies. However, the development of these materials remains a significant challenge. Herein, a series of design rules rooted in computational methods and empirical crystal-chemical analysis is applied to identify a new Cr 3+ -substituted phosphor. The compound GaTaO 4 :Cr 3+ emerged from this study is based on the material's high structural rigidity, suitable electronic environment, and relatively we...

A new family of garnet compounds, Ca 2 LnZr 2 Ga 3 O 12 (Ln=La, Y, Lu, Gd) have been synthesized by high-temperature solid-state reaction method. The crystal structures were characterized by the X-ray diffraction (XRD) and refined by the Rietveld method. The photoluminescence properties, morphology, CIE value, quantum efficiency and thermal stability of Ca 2 LaZr 2 Ga 3 O 12 :Ce 3+ phosphors were investigated in detail to evaluate the use in w-LEDs. The photoluminescence results revealed that these phosphors have a broad excitation band in the blue region ranging from 400 nm to 470 nm and a broad green emission band centered at about 515 nm.The above results indicated that the phosphors could be effectively excited by blue light and may have potentials to be served as green-emitting phosphors for application in w-LEDs.

The photoluminescence spectrum generated by an ordinary phosphor-converted white light-emitting diode (pc-wLED) that combines a blue LED chip with a yellow phosphor or a near-UV LED with red, green, and blue phosphors contains a notable cavity in the cyan region of the visible spectrum (480− 520 nm), which reduces the color quality produced by these lights. Here, we report a new bright blue-cyan-emitting phosphor, NaMgBO 3 :Ce 3+ , which bridges the gap. Rietveld refinements verify the rare-earth substitution while ab initio calculations prove that Ce 3+ occupies the Na + sites. NaMgBO 3 :Ce 3+ is excited by a broad range of near-UV light sources and produces a blue-cyan emission with a high (internal) quantum efficiency, minimal thermal degradation, and zero-chromaticity drift at elevated temperatures. Fabricating a near-UV (λ ex = 370 nm) pumped pc-wLED using NaMgBO 3 :Ce 3+ along with commercially available phosphors demonstrates a well-distributed warm white light with a high color-rendering index (R a ) of 91 and a low correlated color temperature (CCT) of 3645 K. Closing the cyan cavity with NaMgBO 3 :Ce 3+ is ideal for generating a pleasant, full-spectrum warm white light.

Near-infrared (NIR) phosphor-converted light-emitting diode (pc-LED) technology has attracted considerable interest as a next-generation light source for emerging NIR spectroscopic applications. However, discovering efficient broadband NIR phosphors necessary to access the desired long-wavelength (λem ≥ 800 nm) energy window remains a challenge. Here, a new phosphate phosphor, KGaP2O7:Cr3+, emerged from a fundamental study of the AMP2O7 (A = Li, Na, K; M = Al, Ga, Sc, In) family. This material combines all of the requisite properties for the efficient generation of NIR photons, including limited defect formation, minimal electron–phonon coupling, a subtle octahedral site distortion, and well-separated transition metal substitution sites. Photoluminescence spectroscopy indicates that this material emits from 700 to 1100 nm (λmax = 815 nm) with a full width at half-maximum (fwhm) of 127 nm or 1874 cm–1. Exciting the material with a blue LED reveals a quantum yield of 74.4% with an absorption efficiency of 44.8%, resulting in an excellent external quantum efficiency as high as 33.3% from the as-prepared sample. A prototype NIR pc-LED device generated an output power of 473.8 mW and a high photoelectric conversion efficiency (10.7% under 500 mA), demonstrating the potential of applying this phosphor in blue LED-based NIR spectroscopy.

Broadband near-infrared (NIR) light source based on phosphor-converted light-emitting-diode (pc-LED) is crucial for applications in medical diagnosis, food quality analysis, and night vision fields, motivating the development of highly efficient and thermal robust NIR phosphor materials. Herein, a novel Cr 3+ -doped garnet phosphor Y 3 In 2 Ga 3 O 12 :Cr 3+ emerges from a fundamental study of the Ln 3 In 2 Ga 3 O 12 (Ln = La, Gd, Y, and Lu) family. Upon 450 nm excitation, this material presents a broadband NIR emission covering 650−1100 nm with a peak located at 760 nm and a full width at half maximum of 125 nm. This material also possesses an ultrahigh internal quantum efficiency (IQE = 91.6%) and absorption efficiency (AE = 46.6%), resulting in an external quantum efficiency as high as 42.7%. Moreover, the emission intensity of this material at 150 °C maintains 100% of the initial intensity, showing a rare zero-thermalquenching property. Fabricating an NIR pc-LED device by using this material, an excellent NIR output power of 68.4 mW with a photoelectric efficiency of 15.9% under 150 mA driving current can be obtained, which exhibits much better performance than the devices fabricated by using some reported efficient NIR materials. Therefore, this work not only provides an ultraefficient and thermally robust broadband NIR material for spectroscopy application but also contributes to the foundation of design rules of NIR materials with high performance.

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