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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]

Exploring green phosphors with satisfactory peak position (525–535 nm) and full width at half-maximum (FWHM) to replace the commercial narrow-band green β-SiAlON:Eu2+ phosphor (λ em = 540 nm, FWHM = 54 nm) is crucial for realizing wide-gamut full-color liquid crystal display (LCD) devices. Here, taking the UCr 4 C 4 -type tetragonal phase RbNa 3 (Li 3 SiO 4) 4 :3%Eu2+ (RN 3 (LSO) 4 :Eu2+) blue phosphor as starting model, we substitute Na+ with Rb+ to synthesize a series of Rb 1+x Na 2.97-x (Li 3 SiO 4) 4 :3%Eu2+ (0.1 ≤ x ≤ 2.5) (R 1+x N 2.97-x (LSO) 4 :Eu2+) phosphors that exhibit tunable emission from blue to green. We demonstrate that Rb+-substitution triggers tetragonal-to-monoclinic phase transition, making Eu2+ ions enter two new, cuboid-like Rb and Na sites and resultant green emission. With optimized content of Rb+, Rb 3 Na(Li 3 SiO 4) 4 :3%Eu2+ (R 3 N(LSO) 4 :Eu2+) green phosphor not only shows appropriate peak position (∼526 nm) and FWHM (∼43 nm) compared to β-SiAlON:Eu2+ phosphor, but also high internal quantum efficiency (IQE) of 90.2% and superior thermal stability (integrated emission intensity at 150 °C is 105.7% of room-temperature performance). Using the green R 3 N(LSO) 4 :Eu2+ phosphor, white light-emitting diode prototype shows a wide-color-gamut (111.2% National Television System Committee, NTSC). This work demonstrates that as-prepared green R 3 N(LSO) 4 :Eu2+ phosphor has a potential application in LCD backlight display, and may stimulate more researches on exploring high-performance narrow-band UCr 4 C 4 -type phosphors. • Achieving high-performance narrow-band green Rb 3 Na(Li 3 SiO 4) 4 :Eu2+ phosphor by substituting Na with Rb that not only exhibits appropriate peak position (526 nm) and FWHM (43 nm) but also high IQY of 90.2%. • Rb 3 Na(Li 3 SiO 4) 4 :Eu2+ green phosphor shows good thermal stability properties with an integrated emission intensity of 105.7% at 150 °C. • Using the green Rb 3 Na(Li 3 SiO 4) 4 :Eu2+ phosphor, high-quality WLED can cover 111.2% of the color space of NTSC. [ABSTRACT FROM AUTHOR]

Abstract: Si4+ was introduced to the lattice of LiEuMo2O8 by solid-state reaction to prepare a new kind of red-emitting LiEuMo2−x Si x O8 (0

• In Sr 3 Ce(PO 4) 3 :Eu2+, the successive substitution of Sr by Ca causes microstructural transformation of PO 4 tetrahedrons from disordered state to ordered state. • The disorder-to-ordered microstructural variation of PO 4 anion-groups remotely controls Eu2+ emissions, yielding adjustable emission from yellow-green to yellow and then green emission. • This work provides a deeper understanding on how structural ordering degree affects the local structures of Eu2+ centers. Spectrally tunable phosphors have been extensively studied for their potential applications in phosphor-converted white light-emitting diodes and display devices. Herein, we synthesize a series of color-tunable (Sr 2.95-x Ca x)Ce(PO 4) 3 :0.05Eu2+ (x = 0–2.95) phosphors via solid-state reaction, which are designed by using eulytite-type phosphate with different PO 4 structural ordering, viz., Sr 3 Ce(PO 4) 3 :Eu2+ with disordered state of PO 4 tetrahedrons, and Ca 3 Ce(PO 4) 3 :Eu2+ with ordered state of PO 4 tetrahedrons. In Sr 3 Ce(PO 4) 3 :Eu2+, the successive substitution of Sr by Ca causes microstructural transformation of PO 4 tetrahedrons from disordered state to ordered state. Strikingly, the disorder-to-ordered microstructural variation of PO 4 anion-groups remotely controls Eu2+ emissions, yielding adjustable emission from yellow-green to yellow and then green emission and fine tailoring of photoluminescence excitation spectra, which are demonstrated by an in-depth local structure analysis of X-ray, nuclear magnetic resonance and electron paramagnetic resonance. This work provides a deeper understanding on how structural ordering degree affects the local structures of Eu2+ centers. [ABSTRACT FROM AUTHOR]

Exploring broadband yellow phosphors capable of covering the cyan to red region is an effective approach to achieve high-performance phosphor-converted white light-emitting diodes (pc-WLEDs). Herein, we synthesized a series of VO 4 -activated ultra-broadband KSrP 1−x V x O 4 (0.1 ≤ x ≤ 1) yellow phosphors via high temperature solid-state reaction. Successive substitution of P5+ with V5+ causes a slight expansion of the lattice constant and induces several highly localized energy-levels within the forbidden band. Density functional theory calculations confirm that these newly appeared sharp-line energy-levels are attributed to the constructed VO 4 anionic groups. With the optimized V5+ content, the KSrP 0.7 V 0.3 O 4 phosphor exhibits an ultra-broadband yellow emission centered at 537 nm under 355 nm excitation. Impressively, its full width at half maximum is up to 181 nm, exceeding that of most reported counterparts. At 105 °C, the KSrP 0.7 V 0.3 O 4 sample experiences an emission loss of 53%. A WLED device is fabricated by using phosphor blend of KSrP 0.7 V 0.3 O 4 yellow phosphor and the commercial BaMgAl 10 O 17 : Eu2+ blue phosphor and a 355 nm NUV LED chip, demonstrating bright white emission with high color rendering index (CRI) of 90 and suitable correlated color temperature of 5953 K. These findings indicate that this phosphor has great potential for achieving high CRI WLEDs. • VO 4 -activated ultra-broadband KSrP 1-x V x O 4 phosphors were synthesized via solid-state reaction. • Under 355 nm excitation, the optimal KSrP 0.7 V 0.3 O 4 phosphor has an ultra-broadband yellow emission. • The FWHM of the resultant KSrP 0.7 V 0.3 O 4 phosphor has an ultra-broadband yellow emission. • The prepared WLED shows a high CRI of 90 and a suitable CCT of 5953 K. [ABSTRACT FROM AUTHOR]