Efficient Broadband Near‐Infrared Emission in the GaTaO₄:Cr³⁺ Phosphor

Abstract

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...

Highly Efficient and Stable Near‐Infrared Broadband Garnet Phosphor for Multifunctional Phosphor‐Converted Light‐Emitting Diodes

“…[ 14 ] Many studies choose Cr 3+ as activator, such as GaTaO 4 :Cr 3+ , NaScGe 2 O 6 :Cr 3+ , BaMgAl 10 O 17 :Cr 3+ , GdAl 3 (BO 3 ) 4 :Cr 3+ , LiGaP 2 O 7 :Cr 3+ , MgTa 2 O 6 :Cr 3+ , and LiScGeO 4 :Cr 3+ . [ 6,15 ] Among the many Cr 3+ ‐doped NIR phosphors, the garnet structured phosphor was widely studied for its unique luminescence modulation properties. Its structural form is A 3 B 2 C 3 O 12 , A form an eight‐coordinated dodecahedron AO 8 with the surrounding O 2− , while B and the surrounding O 2− form a six‐coordinated octahedron BO 6 , and finally C forms a four‐coordinated tetrahedron CO 4 with the surrounding O 2− .…”

“…

light in this range is known as the first biological window, and the NIR radiation can effectively penetrate biological tissues, which means that a non-destructive and non-invasive diagnosis of the human physiological state can be performed by a perceptible penetration depth in biological tissues. [6] For plant cultivation, red/ photosensitive pigments (PR) and far-red/ photo sensitive pigments (PFR), two pigments indispensable for plant growth, have a specific absorption in the NIR region, and PFR has a strong absorption peak at 730 nm. [7] Various NIR-emitting materials have been developed for halogen lamps, lightemitting diodes (LEDs), organic LEDs (OLED), and phosphor-converted LEDs (pc-LEDs).

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Luminescence properties of Cr3+-doped near-infrared emissive fluoroyttrates for light-emitting diodes

“…29,30 The corresponding PL spectra exhibit broad NIR emission bands from 650 to 900 nm, originating from the spin-allowed 4 T 2 → 4 A 2 transition of Cr 3+ . 31 Specifically, the corresponding emission peaks coming from the KNYF:Cr, RNYF:Cr and CNYF:Cr phosphors are situated at 758, 766 and 786 nm, along with the FWHM values of 98, 102 and 104 nm (Fig. 2b), respectively.…”

Enhancement of Near‐Infrared Phosphor Luminescence Properties via Construction of Stable and Compact Energy Transfer Paths

“…also demonstrated that Cr 3+ ions prefer to occupy Ga 3+ ions rather than Ta 5+ ions by density functional theory (DFT) calculations. [ 31 ] It was further demonstrated by DFT calculations that the formation energy of Yb 3+ substitution for Ta 5+ ions is lower compared to that of Cr 3+ ions substitution for Ta 5+ ions, which is a good indication that Yb 3+ ions prefer to occupy Ta 5+ ions compared to Cr 3+ ions (Table S2, Supporting Information). Since once Cr 3+ /Yb 3+ ions replace Ta 5+ ions, defects will occur due to unequal charges, in order to verify whether there are defects, the TL spectra of GaTaO 4 :0.005Cr 3+ , x Yb 3+ ( x = 0–0.020) were tested and shown in Figure S3b, Supporting Information.…”