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). Among them, halogen lamps have continuous ultra-broadband spectral properties from visible to NIR, but their low luminous efficiency, high operating temperature, and long response time limit their applications. [8] NIR LEDs overcome most of the drawbacks of halogen lamps, but the narrow fullwidth at half maximum (FWHM) and the LED arrangement luminous unevenness also severely limit their utilization at scale. [9] OLEDs are disappointing in terms of efficiency or temperature resistance, even though they have good applicability. [10] The most suitable solution may be the development of NIR pc-LEDs combining InGaN blue LED chips with broadband NIR phosphors. It satisfies both the ultra-broadband spectral emission and the requirements of compactness, efficiency, portability, and low cost. [11] For this purpose, broadband NIR phosphors that are well matched to the blue LED chips need to be developed.Many NIR broadband phosphors based on inorganic matrixdoped activators have been reported so far, [12] however, most of them have disadvantages such as unsuitable NIR emission wavelength, unstable emission intensity at high temperature, and low luminescence efficiency, which greatly limit their applications in various fields. Cr 3+ ions exhibit broadband absorption in the ultraviolet-visible spectral range, which stems from its unique 3d 3 electronic structure. [13] In addition, Cr 3+ ions can display tunable narrowband or broadband spectrum from 600-1600 nm, depending on whether they are in a strong or weak Broadband near-infrared (NIR) phosphor-converted light-emitting diodes (pc-LED) are ideal light sources to meet the next generation of NIR spectroscopy. However, NIR phosphors have numerous problems such as low quantum yields (QY) and low thermal stability. In this work, a series of Gd 3 Y x In x Ga 5-2x O 12 :Cr 3+ NIR broadband phosphors with high internal quantum yields (IQYs) and high thermal stability are discovered by uniquely replacing GaO 6 in Gd 3 Ga 5 O 12 with Y 3+ and In 3+ in a co-doped manner through cation modulation. Under 449 nm excitation, Gd 3 Y 0.5 In 0.5 Ga 4 O 12 (GYIG):yCr 3+ depicts emission from 650 to 1050 nm with a full-width at half maximum (FWHM) of 134 nm. The emission intensity reaches its optimum value at y = 6%, while the IQY reaches an impressive 81.8% and, at 375 K, the emission intensity r...

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Broadband near-infrared (NIR) phosphors are necessary materials for developing portable NIR light sources. Moreover, exploiting an NIR phosphor with a main peak located beyond a wavelength of 900 nm remains a challenge because this spectral range has great potential in biological nondestructive testing and solution testing. In this study, a range of Cr 3+ -doped ZnTa 2 O 6 (ZTO) phosphors were completely synthesized by a solid-state method, which show broadband Cr 3+ emission centered at 935 nm with a large full width at half maximum (FWHM) of 185 nm due to two distorted octahedral sites. A packaged phosphor-converted light-emitting diode (pc-LED) device is used to penetrate a 5-cm-thick chicken breast and identify diverse solutions based on differences in the measured transmission spectra. The results indicate broad application prospects in the field of biological tissue penetration and solution analysis.

Phosphors with the emission spectra located at the biological window I (650–950 nm) are significant for biological imaging. In this work, a series of deep red and near-infrared phosphors InMgGaO4: xCr3+ and In0.9‑y MgGaO4: 0.1Cr3+, yAl3+ are designed and successfully synthesized by a high temperature solid state method. InMgGaO4 is selected as the host considering its special crystal structure that one of the Mg/Ga–O bonds is affected by the surrounding environment. Therefore, when Cr3+ is substituted into the lattice, the longer Mg/Ga–O bonds are easily broken, which provides a tunable crystal field. The emission spectra of InMgGaO4: xCr3+ cover from 650 to 1200 nm, including one sharp line emission peak (peak 1) and two broad emission bands (peak 2 and peak 3). The Racha parameters D q/B and the decay curves are analyzed to distinguish the origins of these three peaks. Meanwhile, these three emission peaks show different degrees of red shift, which is related to the covalency, crystal field splitting (D q), bond breaking of Mg/Ga–O, and decrease of band gap. However, comparing with the luminescent property of Cr3+ single doped samples, In0.9‑y MgGaO4: 0.1Cr3+, yAl3+ shows a contrasting luminescence property and the reason is analyzed. In summary, the emission spectra of these samples can be tuned between a narrow peak and broad band continuously by controlling the concentration of Cr3+ ions or Al3+ ions, which shows a potential application in biological imaging.

The rapid development of near‐infrared (NIR) spectroscopy urgently requires the exploration of NIR‐emitting phosphors with excellent luminescence properties. Herein, GaTaO4:Cr3+,Yb3+ NIR phosphor with excellent luminescence properties is reported, which exhibits ultra‐broadband NIR emission with a full width at half maximum of 300 nm, good thermal stability of 90%@423 K, and most remarkably, high internal quantum efficiency of 95.5% and external quantum efficiency of 44.79%. Such outstanding luminescence properties mainly give the credit to the unique sandwiched structure of GaTaO4:Cr3+,Yb3+, in which layers of Yb3+ ions (activator) are sandwiched between layers of Cr3+ ions (sensitizer), and hence many stable and compact Cr–Yb pairs are formed, so that the energy can be rapidly transferred from Cr3+ to Yb3+, effectively activating the characteristic f–f transition of Yb3+ that is very stable and almost independent of the temperature, and at the same time, the non‐radiative transition of Cr3+ ions can be suppressed to a certain degree. The NIR phosphor‐converted light‐emitting diodes (pc‐LEDs) are fabricated by combining GaTaO4:Cr3+,Yb3+ with blue LED chips, and the application potential is fully demonstrated by non‐destructive food detection, night vision, and vein display. The results provide novel prospects for the design of NIR‐emitting materials with desirable luminescent properties.