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The discovery of phosphors with highly efficient broadband near-infrared emission is urgent for constructing NIR sources for various applications. Herein, we synthesized a series of near-infrared emitting garnet-type (A3B2C3O12) Lu2−xCaAl3.99Cr0.01SiO12:xGd/La and Lu2CaAl3.99−yCr0.01SiO12:ySc/Ga phosphors and systematically investigated the effect of A/B-site substitution on the crystal structure and luminescence properties. Structural and optical analyses revealed that the A/B-site substitution weakened the crystal field strength, further enhancing the broadband emission of the allowed 4T2 → 4A2transition and diminishing the narrow-peak emission of the forbidden 2E → 4A2 transition. As expected, NIR phosphors, exemplified by Lu1.7CaAl3.99Cr0.01SiO12:0.3Gd and Lu2CaAl3.49Cr0.01SiO12:0.5Sc, showed outstanding thermal stabilities at 423 K (150 °C) registering values of 103.02% and 94.91%, with high quantum efficiencies of 80.48% and 85.01%, respectively. In addition, pc-LEDs with broadband NIR output and good optoelectronic properties have been realized, demonstrating the great potential of broadband NIR pc-LEDs for applications. This work not only provides a series of high-efficiency phosphors for NIR pc-LED applications, but also provides a systematic idea and an efficient method to improve the luminescence performance of garnet-type phosphors. [ABSTRACT FROM AUTHOR]

Inorganic lead halide perovskite quantum dots (CsPbX3 QDs (X = Cl, Br, or I)) have attracted more and more attention due to their high absorption coefficient, narrow emission band, high quantum efficiency, and tunable emission wavelength. However, CsPbX3 QDs are decomposed when exposed to bright light, heat, moisture, etc., which leads to severe luminous attenuation and limits their commercial application. In this paper, CsPbBr3@glass materials were successfully synthesized by a one-step self-crystallization method, including melting, quenching and heat treatment processes. The stability of CsPbBr3 QDs was improved by embedding CsPbBr3 QDs into zinc-borosilicate glass. Then, the CsPbBr3@glass was combined with polyurethane (PU) to form a flexible composite luminescent film CsPbBr3@glass@PU. This strategy enables the transformation of rigid perovskite quantum dot glass into flexible luminescent film materials and further improves the photoluminescence quantum yield (PLQY) from 50.5% to 70.2%. The flexible film has good tensile properties, and its length can be strained 5 times as long as the original length. Finally, a white LED was encapsulated by combining CsPbBr3@glass@PU film and red phosphor K2SiF6:Mn4+ with a blue LED chip. The good performance of the obtained CsPbBr3@glass@PU film indicates that it has potential application in flexible liquid crystal displays (LCDs) as a backlight source. [ABSTRACT FROM AUTHOR]

Broadband near‐infrared (NIR) phosphors converted light‐emitting diodes (pc‐LEDs) have attracted tremendous attention for their great potential in NIR spectroscopy applications. Herein, we report on the photoluminescence (PL) properties of Cr3+‐doped Sc(PO3)3, which exhibits a broadband NIR emission centered at 900 nm with a full width at half‐maximum (FWHM) of 161 nm upon excitation at 480 nm. In terms of the examination of spectroscopic parameters, we find that Cr3+ ions occupy a weak crystal field site (Dq/B = 1.94) in the Sc(PO3)3 host with a stronger electron–phonon coupling (Huang‐Rhys factor, S = 5.5), which results in a serious thermal quenching and a low internal quantum efficiency (IQE). Thermal stability and IQE of phosphors can be substantially enhanced by the introduction of Yb3+ ions. In the light of the analysis of excited‐state dynamics, we demonstrate that the enhancement mechanism is ascribed to the efficient Cr3+→Yb3+ energy transfer from the thermal sensitive Cr3+ centers to the thermal stable Yb3+ emitters. An NIR pc‐LED device has been finally fabricated by the combination of a blue‐emitting chip and a Cr3+/Yb3+ codoped Sc(PO3)3 phosphor whose potential application for broadband NIR pc‐LEDs is also discussed. [ABSTRACT FROM AUTHOR]

With great economic benefits, white LEDs (w‐LEDs) have aroused worldwide attention. For phosphor‐converted w‐LED, highly efficient emission and good thermal stability of phosphor are significant parameters in practical application. Here, a yellow‐orange garnet‐structural phosphor, Ba2YAl3Si2O12:xCe3+ (x = 0‐0.1) (BYAS:xCe3+) was developed by solid solution design. The broad emission spectrum of the as‐synthesized phosphor could guarantee the effective increase of the color rendering index when it is combined with the InGaN blue chip. Benefiting from the garnet‐type highly rigid framework, BYAS:xCe3+ exhibits an excellent thermal stability (50%@673K of the initial integrated intensity at 280 K) as well as high absolute quantum efficiency (80.4%@460 nm excitation light). Utilizing the approach of "phosphor‐in‐glass" (PiG), a high‐power warm w‐LED is achieved based on a blue LED plus PiG and the illuminance of this w‐LED device can be as high as 4227 lx. [ABSTRACT FROM AUTHOR]

It is necessary to develop novel high-efficiency red or far-red-emitting LEDs in order to facilitate the phosphor-converted light-emitting diodes (pc-LEDs) for plant growth. This work reports a series of novel far-red emitting (Ba,Sr)LaZnTaO6:xMn4+ phosphors with double perovskite structure synthesized by the traditional high-temperature solid-state reaction (SSR). The crystal structure and morphology of (Ba,Sr)LaZnTaO6 were investigated by high-resolution TEM, SEM, and XRD Rietveld refinement. The photoluminescence properties were systematically explored and analyzed by diffuse reflectance (DR) spectra, photoluminescence emission (PL) and excitation (PLE) spectra, decay curves, and temperature-dependent spectra. Mn4+ ions occupy Ta5+ sites located at the [TaO6] octahedral emitting red light with the peak at 698 nm in BaLaZnTaO6:Mn4+ and 695 nm in SrLaZnTaO6:Mn4+ under n-UV and blue light excitation. The critical quenching concentration of Mn4+ was determined to be 0.008. The concentration quenching mechanism could be a dipole–dipole interaction between the Mn4+ ions. In addition, the PL intensity of (Ba,Sr)LaZnTaO6:xMn4+ phosphors decreases with increasing temperature. The SrLaZnTaO6:xMn4+ sample has better thermal stability than BaLaZnTaO6:xMn4+. Interestingly, (Ba,Sr)LaZnTaO6:0.008Mn4+ exhibits outstanding internal quantum efficiency (IQE ≥ 80%). Finally, the fabricated LEDs were combined with SrLaZnTaO6:0.008Mn4+ phosphors combined with 460 nm InGaN chips, which emit blue and red light. Based on the above properties, the rare-earth-free (Ba,Sr)LaZnTaO6:xMn4+ phosphors have great potential in being applied as far-red emitting phosphors in high-power plant growth LEDS. [ABSTRACT FROM AUTHOR]

High-performance sky-blue pure bromine quasi-2D PeLEDs with a remarkable EQE of 18.5% are achieved through incorporating the triethyl 2-acetylcitrate (TEAC) additive, for simultaneously passivating multiple unsaturated Pb2+ defects and narrowing of the phase distribution. [Display omitted] • Highly-efficient sky-blue quasi-2D PeLEDs are demonstrated by incorporating the multifunctional triethyl 2-acetylcitrate (TEAC) additive. • The TEAC additive can simultaneously passivate multiple bromine vacancy defects and tune the phase distribution. • A remarkable EQE of 18.5% is achieved in sky-blue PeLEDs, representing the best-performing pure bromine blue PeLEDs to date. • This work provides a reliable approach to boost the performance of blue PeLEDs. Quasi-2D perovskite light-emitting diodes (PeLEDs) are considered as one of the most promising candidates for next-generation displays. Yet, the unstable electroluminescent spectra and inferior performance of blue PeLEDs hinder their commercial use. Herein, we demonstrate highly efficient quasi-2D pure bromide (QPB) sky-blue PeLEDs based on an oxygen-rich triethyl 2-acetylcitrate (TEAC) additive. The TEAC additive contains four C = O functional groups, offering several coordination sites to simultaneously passivate multiple bromine vacancy defects. Furthermore, it inhibits the growth of large n (n ≥ 5) phases to achieve narrow phases distribution. As a result, the TEAC-modified PeLEDs show sky-blue emission at 494 nm, with maximum current efficiency and external quantum efficiency up to 29.1 cd/A and 18.5 %, respectively. Moreover, the T 50 lifetime of TEAC-modified PeLED is about 25 times higher than that of pristine PeLEDs. Our results provide a reliable approach to realizing high-efficiency blue quasi-2D PeLEDs. [ABSTRACT FROM AUTHOR]

By hetero-valence substituting Ba2+-Si4+ for Lu3+-Al3+ pair in Lu 3 Al 5 O 12 : Ce3+, a new green phosphor Ba 1.5 Lu 1.5 Al 3.5 Si 1.5 O 12 : Ce3+ (BLAS: Ce3+) has been obtained. It crystallizes in garnet structure with space group Ia -3 d (230). In the structure, Ba2+ ions are incorporated into both dodecahedral Lu3+ and octahedral Al3+ sites while Si4+ ions only occupy tetrahedral Al3+ sites. Under the blue light irradiation of 450 nm, an intense green light peaking at 520 nm was observed and the PL spectrum can be fitted in two Gaussian components, due to the crystal field splitting of Ce3+ 5 d states under D 2 symmetry constrains. The optical doping concentration of BLAS: Ce3+ is 6% mol, of which the IQE and EQE are 89.1% and 51.8%, respectively. Furthermore, this sample exhibits an extremely good thermal stability, i.e. the integrated emission intensity is still more than 90% of the initial intensity at 480 K. Then, a w-LED device was fabricated from this new green phosphor BLAS: Ce3+ and commercial red phosphor (Ca,Sr)AlSiN 3 : Eu2+, which shows a quite high color rendering (Ra = 88.2) and a relatively low color temperature 4772 K. Besides, the phosphor exhibits a stable chromaticity under different acceleration voltages. The phosphor may be promising material for the development of solid-state lighting and display systems. [ABSTRACT FROM AUTHOR]

An effective defect passivation strategy is demonstrated by introducing the diethylene glycol bis(3-aminopropyl) ether (DGBE) additive to suppress the non-radiative recombination. Thus, high-performance red PeLEDs are realized with a maximum EQE of 24.2%, which provides a rational strategy for boosting the performance of red PeLEDs. [Display omitted] • The defect-induced nonradiative recombination is effectively suppressed by introducing the Lewis base additive of diethylene glycol bis(3-aminopropyl) ether (DGBE). • The PLQYs of the DGBE-modified perovskite films significantly increase from 39% to 80%. • High color purity and efficient red PeLEDs is achieved with a maximum EQE of 24.2%, representing one of the best performing red PeLEDs reported so far. • This work provides a reliable approach to promote the development of highly efficient red PeLEDs. Quasi-two-dimensional perovskites are promising emitters for red light-emitting diodes. However, the practical application of red perovskite light-emitting diodes (PeLEDs) is still limited by the defect-induced nonradiative recombination. In this study, we demonstrate efficient red PeLEDs by introducing the diethylene glycol bis(3-aminopropyl) ether (DGBE) additive. The coupling effect between oxygen (O) atoms in DGBE and unsaturated Pb2+ not only regulates crystallization, but also passivates defects. Benefiting from the reduced defect densities and enhanced radiative recombination efficiencies, the photoluminescence quantum yield (PLQY) increases from 39 % to 80 %. Consequently, we achieve high-performance red PeLEDs with a maximum external quantum efficiency of 24.2 %, which provides a reliable approach to promote the development of highly efficient red PeLEDs. [ABSTRACT FROM AUTHOR]

Abstract Self-activated phosphors could convert high energy light into visible light from the internal ion groups of host lattice before externally introducing luminescent ions. In this work, we propose a facile route to synthesize self-activated oxyfluorotungstate (Na 2 WO 2 F 4) phosphor. Excited by the UV light, the emission spectrum covers nearly the entire visible light region. After careful analysis of the first principle calculation results and other sufficient investigation, it is believed that the efficient emission of Na 2 WO 2 F 4 phosphor comes from the strong parity-allowed absorption of O-2 p to W-5d charge transfer band. Moreover, the quantum efficiency of Na 2 WO 2 F 4 phosphor reaches up to 76% at room temperature. However, the increase of temperature not only lowers the intensity of the PL emission and the quantum efficiency but gives rise to a blue shift of the emission maxima, due to the phonon interaction with the luminescence center in a vibrating crystalline environment. Graphical abstract Image 1 Highlights • A self-activated phosphor Na 2 WO 2 F 4 was obtained by a facile route. • The emission spectrum of Na 2 WO 2 F 4 covers nearly the entire visible light region. • The quantum efficiency reaches up to 76% at room temperature. • Thermal quenching and high-energy shift of Na 2 WO 2 F 4 were observed and analyzed. [ABSTRACT FROM AUTHOR]

Near-infrared (NIR) persistent luminescence (PersL) phosphors, which exhibit unique properties of high signal-to-noise ratio and wide excitation spectral region, have attracted more and more attention in the next-generation high-capacity storage system. In this paper, a multi-spectral excited NIR PersL phosphor, Zn 1.25 Ga 1.5 Ge 0.25 O 4 : Cr3+ (ZGG: Cr3+) which is developed by doping ZnGa 2 O 4 : Cr3+ with tetravalent Ge4+, has been successfully synthesized. Rietveld refinements show that Ge4+ ions enter into octahedral sites by substituting Ga3+ ions and the hetero-valence substitution enriches the charged defects. This PersL phosphor exhibits a zero-phonon lines emission of Cr3+ [2E→4A 2g ] with the maximum at 698 nm and the maximum values of IQE and EQE can reach to 60.3% and 22.4%, respectively. An intense photostimulated persistent luminescence (PSPL) can be repeatedly obtained by NIR laser stimulation in a period of more than 48 h (write-out) when the ZGG: Cr3+ phosphor illuminated by an ultraviolet-light (UV) (write-in). In addition, adopting thermoluminescence (TL) method, we studied the electron motion in traps and found a specific PersL mechanism which will be reported in this work. All these results demonstrate that the ZGG: Cr3+ phosphor has promising applications in optical information storage. • A near-infrared emission persistent luminescent ZGG: Cr3+ phosphor for optical information storage was synthesized. • The IQE and EQE of the phosphor can reach 60.3% and 22.4%, respectively. • An intense photostimulated persistent luminescence can be repeatedly obtained by NIR laser stimulation. [ABSTRACT FROM AUTHOR]

An oxide-based green emitting phosphor, SrAl 2 Si 2 O 8 : Mn2+ (SASO: Mn2+) deriving from the feldspar mineral model has been successfully synthesized by a facile solid-state reaction. Upon 450 nm blue-light excitation, brightness narrow-band green light peaking at 517 nm with a full-width at half-maximum (fwhm) of 26 nm can be obtained. Owing to the narrow band emission, the CIE chromaticity coordinates are (0.182, 0.745) and the color purity of SASO: Mn2+ is determined to be 78.3%. Meanwhile, the internal quantum efficiency (IQE) of the representative sample can reach up to 45.6% under 450 nm. In addition, the phosphor exhibits an extremely thermal stability, i.e., the integrated emission intensity at 420 K still remains 92% of the initial value. Furthermore, w-LED device fabricated from optimized phosphor SASO: Mn2+ (green), commercial phosphor KSF: Mn4+ (red) and blue LED chip can cover 120% National Television System Committee standard (NTSC) value. All these results suggest that the Mn2+ ion activated green emitting phosphor has great potential for wide gamut w-LEDs backlights. • A narrow-band green-emitting Mn2+ doped SrAl 2 Si 2 O 8 phosphor was synthesized. • The phosphor has a broad excitation band, which can match well with blue chips. • The phosphor has excellent thermal and color stability, high color purity. [ABSTRACT FROM AUTHOR]