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 generation of red phosphors of complex fluoride matrices activated with Mn has gained a broad interest in getting high color quality and low color temperature of solid-state white light-emitting diodes (WLEDs). However, besides their instability toward moisture, the extremely irregular and nonuniform morphologies of these phosphors have limited their practical industry applications. In the present study, a novel type of KScF:Mn red phosphor with highly regular, uniform, and high color purity was obtained successfully through a facile coprecipitation route under mild conditions. The crystal structure was identified with aids of the powder X-ray diffraction, Rietveld refinement, and density functional theory calculations. The prototype crystallizes in the space group Fm3 m with a cubic structure, and the lattice parameters are fitted well to be a = b = c = 8.4859(8) Å and V = 611.074(2) Å. The Mn ions occupy Sc sites and locate at the centers of the distorted ScF octahedrons. A wide band gap of approximately 6.15 eV can provide sufficient space to accommodate impurity energy levels. Unlike most other Mn ion-activated fluoride phosphors, the as-prepared KScF:Mn phosphors demonstrate highly uniform and regular morphologies with shapes transforming from cube to octahedron with increasing Mn ion concentration. Under blue light excitation, the as-prepared KScF:Mn sample exhibits intense sharp-line red fluorescence (the strongest peak located at 631 nm) with high color purity. An excellent recovery in luminescence upon heating and cooling processes implies high stability of KScF:Mn. Furthermore, a warm WLED fabricated with blue GaN chips merged with the mixture of KScF:Mn and the well-known commercial YAG:Ce yellow phosphors exhibits wonderful color quality with lower correlated color temperature (3250 K) and higher color-rendering index ( R = 86.4). These results suggest that the KScF:Mn phosphor possesses stupendous potentiality for practical applications.

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With the repaid development of NIR pc-LED, it is urgent to develop novel NIR phosphor with broadband emission, strong luminescence and high thermal stability. Here, three isotypic garnet fluorides Na3X2Li3F12...

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is an important commercial phosphor for high-power white light-emitting diodes due to its strong resistance toward thermal quenching and sufficient emission efficiency. However, the underlying mechanisms of this high performance is still a mystery. Also, the emission properties of Ce 3+ in two kinds of crystallographic sites are currently in dispute. Here, we confirmed the yellow emission ascribed to Ce La(2) luminescence center and proposed a blue emission owning to Ce La(1) luminescence center through both theoretical and experimental methods. Particularly, we find an unusual efficient and fast energy transfer from Ce La(1) to Ce La(2) due to a large spectral overlap between the emission of Ce La(1) and the absorption of Ce La(2) , and efficient electron transfer from defects to 5d orbital at high temperature, which shows high relevance to the highly efficient yellow emission and thermal stability of this material. This study presents a full and new understanding toward this special phosphor and provides useful insights into designing highly efficient and thermally stable luminescent materials for future lighting.