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Cr3+‐activated near‐infrared (NIR) phosphors have gained extensive attention for use in NIR phosphor‐converted light‐emitting diodes (pc‐LEDs), which are required for smart NIR spectroscopy techniques. Nevertheless, obtaining broadband NIR‐emitting phosphors with outstanding thermal stabilities and photoluminescence (PL) efficiencies remains a significant challenge. Herein, considering NaSr2XGe5O14 (X = Al, Ga, Sc, and In) as hosts, which possess a large band gap and multiple sites for the substitution of Cr3+ ions. NaSr2XGe5O14:Cr3+ phosphors are successfully prepared using a solid‐state reaction technology. Upon blue light excitation, the phosphors cover a broad NIR emission band in 650–1100 nm region. Notably, an abnormal blueshift and PL enhancement are observed following the substitution of Al/Ga with Sc/In. In particular, the PL internal quantum efficiency is improved from 34.5% (NaSr2GaGe5O14: Cr3+) to 87.5% (NaSr2ScGe5O14: Cr3+). Moreover, the manufactured NIR pc‐LED exhibited an exceptional photoelectric efficiency of 17.7% with an NIR output power of 10.2 mW at 20 mA, and its potential application in nondestructive detection is demonstrated. [ABSTRACT FROM AUTHOR]

The Cr3+-doped near-infrared (NIR) phosphors have been extensively investigated owing to their promising applications in biomedicine, food safety detection, and night vision surveillance. However, achieving broadband (FWHM > 160 nm) NIR emission is still challenging. In this paper, novel Y2Mg2Ga2−xSi2O12:xCr3+ (YMGS:xCr3+, x = 0.005–0.08) phosphors were prepared by a high-temperature solid-state reaction. The crystal structure, photoluminescence properties of the phosphor, and the device performance of a pc-LED were researched in detail. When excited at 440 nm, the YMGS:0.04Cr3+ phosphor exhibited broadband emission in the range of 650–1000 nm, peaking at 790 nm with a full width at half-maximum (FWHM) of up to 180 nm. The wide FWHM of YMGS:Cr3+ is conducive to its extensive application in NIR spectroscopic technology. In addition, the YMGS:0.04Cr3+ phosphor could maintain 70% of the initial emission intensity at 373 K. By combining the commercial blue chip with the YMGS:0.04Cr3+ phosphor, the resulting NIR pc-LED demonstrated a near-infrared output power of 14 mW with a photoelectric conversion efficiency of 5% at a drive current of 100 mA. This work provides a broadband emission NIR phosphor option for NIR pc-LED devices. [ABSTRACT FROM AUTHOR]

For high-efficiency lighting and wide color gamut backlight display, high-quality narrow-band red phosphors for WLEDs are still in high demand. Herein, a novel red-emitting fluoride phosphor Cs2NaGaF6:Mn4+ was successfully synthesized by a simple two-step co-precipitation method and exhibits ultra-intense zero-phonon lines (ZPLs) and long wavelength phonon sidebands under 468 nm blue light irradiation. The ZPL emission peak of Cs2NaGaF6:Mn4+ was located at 627 nm, which is much stronger than its υ6 vibration peak, more matchable with the eye-sensitive region of humans, and beneficial for obtaining higher luminous efficiency of WLEDs. Interestingly, the υ6 vibration peak of this red phosphor is at 636.5 nm, which is larger than that of the common fluoride phosphor A2BF6:Mn4+ (usually at about 630 nm, represented by K2SiF6:Mn4+) at about 6.5 nm. Thanks to the longer wavelength of the υ6 vibration peak, the chromaticity coordinates (0.7026, 0.2910) with a larger x-coordinate value were realized, leading to a potentially wider color gamut of WLEDs. In addition, this phosphor has high thermal stability and its emission intensity at 423 K remains 93.7% of the initial intensity at room temperature. The lumen efficiency of WLED1 packaged with a mixture of Cs2NaGaF6:Mn4+ and YAG:Ce3+ on the InGaN blue chip is 115.7 lm W−1 with the color temperature (Tc) = 3390 K and the colour rendering index (Ra) = 92.5 under 20 mA driving current. The chromaticity coordinates of WLED2 packaged with Cs2NaGaF6:Mn4+ and β-SiAlON:Eu2+ on the InGaN blue chip are (0.3149, 0.3262) and the calculated color gamut is up to 118.4% (NTSC). These results indicate that Cs2NaGaF6:Mn4+ red phosphors have promising applications in the high-quality lighting and display fields. [ABSTRACT FROM AUTHOR]

Phosphor-converted light-emitting diodes (pc-LEDs) have important applications in security surveillance and food testing. However, developing new broadband near-infrared phosphors remains an important issue. Herein, the high-temperature solid-state reaction method was applied to synthesize a new type of Cr3+ doped Mg2Al4Si5O18 broadband NIR phosphor which matches a blue LED chip. It exhibits a broadband near-infrared (NIR) phosphor emission with a focus of 856 nm and a full width at half maximum >200 nm after excitation at 453 nm. The optimum concentration of Cr3+ was established to contain 2 mol%. At 398 K, the luminescence intensity is 45.2% of that at 298 K. The power output of NIR pc-LEDs fabricated by incorporating a 450 nm chip and the Mg2Al4Si5O18:0.02 Cr3+ phosphor is 19.69 mW at 300 mA current. Finally, the developed NIR pc-LED shows significant potential for use in night-vision imaging. [ABSTRACT FROM AUTHOR]

A novel Sr2MgB2O6 (SMBO) green-emitting phosphor co-doped with Ce3+–Tb3+ was synthesized at 950 °C via solid-state reactions, and the ultra-narrow-band green emission of Tb3+ was significantly enhanced almost 20 times via energy transfer from Ce3+ to Tb3+. It was found to have a broad excitation band (250 to 400 nm), and the full width at half-maximum (FWHM) of the dominant green emission band around 544 nm was only about 10 nm. The electronic band gap of the SMBO matrix was calculated by density functional theory (DFT) to be 4.60 eV, and this was well verified by the diffuse reflection spectra results. Furthermore, the composition-optimized phosphor SMBO:0.05Ce3+,0.05Tb3+ exhibits excellent thermal quenching resistance (75.3% intensity at 423 K) and relatively high external quantum efficiency (EQE = 48.92%). Finally, two white light-emitting diode (WLED) packages were fabricated via combining a 365 nm n-UV chip, the optimal sample and commercial blue and red phosphors to assess the application potential of the phosphors. The test results indicate that the obtained WLEDs-1 fabricated with K2SiF6:Mn4+ has an outstanding color rendering index (Ra = 85.7) and Commission Internationale de L'Eclairage (CIE) coordinates (0.3242, 0.3334). Meanwhile, the color gamut can reach 87% of the National Television Standards Committee (NTSC) CIE 1931 color gamut. WLEDs-2 fabricated with red emitting CaAlSiN3:Eu2+ produced warm white light with color coordinates of (0.3792, 0.3810), a high color rendering index of 82.3, and a low correlated color temperature of 4065 K. These results reveal the broad prospects of this phosphor for LED-based applications. [ABSTRACT FROM AUTHOR]

• ScP 3 O 9 : Cr3+, shows a broadband NIR emission and peaking at ∼900 nm. • The PL intensity of ScP 3 O 9 : Cr3+ can be enhanced by phase transition. • ScP 3 O 9 : Cr3+, Nd3+, Pr3+ exhibits an excellent PL thermal stability (86 % at 423 K). • The NIR pc-LED device can be applied in non-destructive analysis. Near-infrared (NIR) phosphors play an important role in NIR pc-LEDs. However, NIR phosphor with long wavelength are still suffered from low efficiency and poor thermal stability. Herein, a blue light excitable ScP 3 O 9 : Cr3+ NIR phosphor with an emission peak > 880 nm is reported. Significantly, the PL intensity of ScP 3 O 9 : Cr3+ increased to 241 % when the monoclinic phase changes to cubic. Moreover, by co-doping the cubic ScP 3 O 9 : Cr3+ with Nd3+, Pr3+ ions, the PL internal quantum efficiency (IQE) of the phosphors increased from 62 % to 74 %, and the thermal quenching of the phosphor is suppressed effectively (86 % at 423 K). The energy transfer processes between Cr3+ and Nd3+, Pr3+ ions are proposed to be responsible for the enhancement. Furthermore, an efficient NIR pc-LED was fabricated, and gives a high photoelectric efficiency of 16.5 % (26.8 mW at 60 mA). Finally, multifunctional applications of the NIR device in night-vision and nondestructive analysis were demonstrated. An efficient broadband NIR phosphor ScP 3 O 9 : Cr3+, Nd3+, Pr3+ with excellent thermal stability is prepared to fabricate compact NIR pc-LED based on commercial blue diode chips. The NIR pc-LED device is promising for the applications in non-destructive analysis. [Display omitted] [ABSTRACT FROM AUTHOR]

• A novel red phosphor Ca 9 Nd(PO 4) 7 :Eu3+ was synthesized for the first time. • The occupation and crystalline structure of Ca 9 Nd(PO 4) 7 :xEu3+phosphors were thoroughly determined by DFF simulation and Rietveld refinement. • This phosphor can be efficiently excited by near-ultraviolet light to present intense red light emission. • The phosphor exhibits good property of thermal stability. • The WLED fabricated with Ca 9 Nd(PO 4) 7 :xEu3+ has shown superb color temperature and color purity. A series of Ca 9 Nd(PO 4) 7 :xEu3+ (abbreviates as CNP:xEu3+, where x varies from 0.1 to 0.5) phosphors were prepared via conventional solid-state reaction. The X-ray diffraction (XRD) data and Rietveld refinement suggested a successful preparation of CNP:xEu3+ with no sign of impurities. The structure of CNP:Eu3+ belongs to a trigonal crystal system the same as that of β-Ca 3 (PO 4) 2. Thus, Eu3+ ions should theoretically occupy the Ca sites in CNP. All CNP:xEu3+ phosphors showed red emission under excitation in the near-ultraviolet (n-UV) range. The optimal dosage with the best luminescent performance was found at x = 0.3 with critical interaction radius (Rc) of 15.57 Å. The electric dipole-dipole interaction was suggested to be the reason that leads to concentration quenching. The relative luminous intensity of CNP:0.3Eu3+ phosphor at 373 K can remain 70.4% of the initial value at room temperature (RT). The color purity of CNP:0.3Eu3+ phosphor is 92.8%, which is much higher than many other red phosphors. A white light emitting diode (WLED) fabricated with CNP:Eu3+ exhibited correlated color temperature (CCT) of 4602 K and a high Ra of 74.7. The above results illustrate that Ca 9 Nd(PO 4) 7 :Eu3+ could serve as a promising red phosphor for n-UV WLEDs. [Display omitted] [ABSTRACT FROM AUTHOR]