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...

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needed to excite the electrons from the ground state to the conduction band. However, this strict requirement for highenergy photonic sources which is easily to pose great threat to human body limits their popularity in civil scenes. By comparison, visible light (≈400-700 nm) is harmless to our skin or eyes. In addition, the blue chip based white light emitting diodes are common light sources in nowadays human life. [6] Thus, it is a trend to promote the development of persistent phosphors which can be excited by the visible light. It is worth noting that some persistent phosphors can absorb light with low photon energy such as deep-red or near-infrared (NIR) so that accelerate the release process of trapped electrons, which is the wellknown photostimulation process. [1d] But it is different from the energy storage process (that is photoexcitation), and the latter will be discussed carefully in this paper. To date, some phosphors have been reported to realize the visible light storage and achieved commercial success, such as SrAl 2 O 4 : Eu 2+ , Dy 3+ (green), [7] CaAl 2 O 4 : Eu 2+ , Nd 3+ (blue), [8] Sr 2 MgSi 2 O 7 : Eu 2+ , Dy 3+ (azure), [9] Y 2 O 2 S: Mg 2+ , Ti 4+ , Eu 3+ (red). [10] In addition, Pan et al. have designed Zn 3 Ga 2 Ge 2 O 10 : Cr 3+ in 2011, in which the NIR afterglow can be induced by almost all visible light wavelength. [11] Bessière et al. have proposed a deep-red emissive phosphor ZnGa 2 O 4 : Cr 3+ in 2014, [12] which further enrich the luminous band of afterglow materials.Persistent phosphor, as an eco-friendly energy storage material, usually needs high-energy photonic rays in the storage process, such as ultraviolet (UV) light, X-ray, or even γ-ray. This strict requirement for light source which is harmful to human health greatly limits the popularity of persistent phosphors in the daily life. Here, a novel broadband orange persistent emissive phosphor LiGaO 2 :1%Mn 2+ (LGOM) is reported which supports efficient wide band excitation from UV to green light. The afterglow excited by 470 nm light even reaches ≈80% as intensity as UV excitation. The afterglow of LGOM excited by common blue lamp (450-460 nm) can be pictured by the smart phones for more than 48 h. The mechanism of visible light storage is discussed through the thermal-luminescence measurements. In addition, interestingly, its persistent emissive color can shift from orange-yellow to orange-red after ceasing the excitation source. This unique broadband orange afterglow phosphor which supports efficient wide range visible-light excitation, afterglow color shift, and long-lasting luminescence is expected to have potential applications in the fields of emergency direction, anticounterfeiting, decoration design, etc.