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Fe3+ ions as near‐infrared (NIR) activators are emerging as an alternative to Cr3+.1–5 However, it is a challenge to develop Fe3+‐activated NIR phosphors featuring tunable optical properties, high efficiency, and thermal stability. Herein, we present a series of near‐unity internal quantum efficiency (IQE), wavelength‐tunable and thermal stability NIR‐emitting phosphors Sr2−yCaySc1−xSbO6:xFe3+ (S2−yCyS1−xS:xFe3+). Sr2ScSbO6:1%Fe3+ (SSS:1%Fe3+) phosphor shows broadband NIR emission at 904 nm and near‐unity IQE under excitation at 300 nm. Experimental and theoretical calculation results demonstrate that introduced Ca ions could increase the bandgap value and Debye temperature (ΘD) of host from Eg = 3.702 eV, ΘD = 609 K of y = 0 to Eg = 3.801 eV, ΘD = 692 K of y = 2. Significantly, the resultant S2−yCyS1−xS:1%Fe3+ NIR phosphors show wavelength‐tunable emission from 904 to 952 nm and high IQE of 84.6%–97.5% as well as enhanced thermal stability (I423K/I298K = 76.9%) of Ca2ScSbO6:1%Fe3+ (CSS:1%Fe3+) in comparison with that (I423K/I298K = 70.6%) of pristine sample. We fabricated an NIR light‐emitting diodes (LED) device by using CSS:1%Fe3+ NIR phosphors with ultraviolet LED chip and demonstrated its potential applications in anticounterfeiting, information encryption, and night vision. [ABSTRACT FROM AUTHOR]

Portable near-infrared (NIR) lighting source stimulates great efforts to exploit NIR phosphor-converted LEDs (pc-LEDs) that push the rapid development of broadband NIR-emitting phosphors. Although Cr3+-activated NIR phosphors designed by multisites occupation strategy show significant potential in emission bandwidth, poor spectral stability caused by different thermal quenching behaviors is a brake on practical application due to different local structure around Cr centers. One-site-based NIR phosphors seem to be an effective method to solve aforementioned problem. Herein, we report a type of new ultra-broadband one-site-based NIR-emitting phosphors NaSc 1-x P 2 O 7 :xCr3+ (NSP:xCr3+) with emission at 910 nm and full width at half maximum (FWHM) of up to ∼200 nm. Their FWHM value exceeds all one-site-based Cr3+-activated phosphors and some multiple-sites ones. Structural analysis and low-temperature spectra demonstrate that such impressive broadband NIR emission originates from Cr3+ occupying at single octahedral Sc site. At 425 K, integrated emission intensity of NSP:0.04Cr3+ phosphor maintains 53.8% of room temperature. A NIR pc-LED prototype is fabricated by using NSP:0.04Cr3+ phosphor with a blue LED chip, and its multipurpose applications in non-destructive detection, night vision and analysis of foodstuff are demonstrated. These findings indicate that broadband NSP:0.04Cr3+ NIR phosphor enabled by one-site occupation strategy has potential prospect for multipurpose NIR pc-LEDs applications. [ABSTRACT FROM AUTHOR]

High efficiency red phosphors, showing spectral range of 610–620 nm and a narrow-line emission, are helpful for achieving high color rendering index (CRI) and low correlated color temperature (CCT) phosphor-converted white-light diodes. Red phosphors activated by trivalent europium (Eu 3+ ) thus have attracted a renewed interest for pc-WLEDs. In our case, we prepare a series of Pb 2+ -doped LiEuMoO 8 red-emitting phosphors by solid-state reactions. The introduction of Pb 2+ ions expands and distorts slightly the unit cell volume of LiEuMo 2 O 8 matrix, and red-shifts the charge transfer absorption (CTA) band of LiEuMo 2 O 8 , which are demonstrated by X-ray powder diffraction, absorption spectra and micro-Raman spectra. Photoluminescence and photoluminescence excitation spectra results show that the excitation efficiency of Eu 3+ is improved significantly in the near ultraviolet region when Pb 2+ ions are doped into the host lattice. At x=0.015, the red-emitting intensity of LiEuMo 2 O 8 is enhanced by 50%, and the internal quantum yields is 53% under excitation at 395 nm. The enhanced red emission is discussed in term of the relaxation of parity-forbidden selection rules for trivalent europium luminescent center, and the sensitization effect of Pb 2+ as a sensitizer for Eu 3+ ions is negligible in LiEuMo 2 O 8 under near ultraviolet excitation. [ABSTRACT FROM AUTHOR]