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The phosphor-converted light emitting diode (pc-LED) is an efficient light source to adjust growth rhythm and raise yield of plant. Blue and red light play the dominant role in the process of plant growth, thus it is meaningful to search the blue-red dual emission phosphors with high quantum field and better thermal stability for developing plant growth LED. Herein, the blue-red dual emission phosphors were synthesized by co-doping Sb3+ and Ho3+ into the Cs 2 NaLuCl 6 , which emitted blue (454 nm) to red (657 nm) light with increasing the content of Ho3+ to 25% and their relative intensity could be tuned through adjusting the concentration of Ho3+ due to the efficient energy transfer from Sb3+ to Ho3+. The intensity of blue emission from Sb3+ and red emission from Ho3+ could maintain 78.4 and 75.8% of the room temperature at 150 °C, respectively. Furthermore, the spectra of fabricated blue and red LEDs match well with the absorption of carotenoid, Phytochrome and Chlorophyll b , implying the samples possess great application potential in plant growth LED. Blue-red double color emitting phosphor Cs 2 NaLuCl 6 :Sb3+, Ho3+. [Display omitted] [ABSTRACT FROM AUTHOR]

Cr3+ activated near‐infrared (NIR) phosphors are getting unprecedented attention to fabricate the broad band NIR light emitting diodes (NIR‐LEDs) for nondestructive detection, bio‐imaging, and night vision. However, it remains a major challenge to obtain ultrabroadband NIR emitting phosphor with excellent quantum yield (QY). Here, a broadband NIR emitting phosphor Mg7Ga2GeO12:Cr3+ (MGGO: Cr3+) ranging from 600 to 1300 nm with an outstanding QY (93%) and large full width of half maximum (FWHM = 226 nm) is developed, in which the site occupancy tendency of Cr3+ in MGGO host is discussed in detail through combining the structure optimization and the first‐principles theory calculation with luminescent properties at low temperature. After that, the emission intensity of MGGO:Cr3+ is improved through partial substitution of Mg2+ by alkaline‐earth ions Ca2+, Sr2+, or Ba2+, and the luminescence enhancement mechanism is also investigated. Furthermore, the NIR pc‐LED device is fabricated by combining 450 nm blue LED chip with the brightest phosphor MGGO:Cr3+/Ba2+, and its potential applications are evaluated in the field of nondestructive detection, night vision, and bio‐imaging. [ABSTRACT FROM AUTHOR]

Lead-free halide double-perovskite materials have been given extensive attention due to the charming fluorescent property and simple synthesis process. Their strong electro-acoustic coupling effects endow the materials with wideband emission properties and the tremendous potential application in white light emitting diodes (w-LEDs). Herein, the blue (456 nm) and yellow (578 nm) light emitting phosphors with broad band emission were synthesized by introducing the Bi3+ and Te4+ into the structure-stable and low toxicity Cs 2 ZrCl 6 materials, respectively. The blue and yellow emission from 3P 1 → 1S 0 transitions of Bi3+ and Te4+ were achieved in Cs 2 ZrCl 6 : 7%Bi3+ and Cs 2 ZrCl 6 : 3%Te4+, where the large full width at half maximum (FWHM) values of 45 and 101 nm were attributed to the large Huang-Rhys factor and electro-acoustic coupling strength. The white LED fabricated through combining the 365 nm chip with the prepared blue and yellow phosphors exhibited wideband white light emission ranging from the 400–750 nm with correlated color temperature (CCT) 5028 K and good color rendering index (CRI) 84. White LEDs fabricated through combination the n-UV LED chip with the Bi3+ and Te4+ solely doped Cs 2 ZrCl 6 blue and yellow emitting phosphors. [Display omitted] • Phosphors Cs 2 ZrCl 6 : Bi3+ and Cs 2 ZrCl 6 : Te4+ were prepared, respectively. • They exhibit bright blue and yellow emission, respectively. • White LEDs was fabricated by combination of the prepared phosphor and 365 LED chip. [ABSTRACT FROM AUTHOR]

Obtaining phosphors with white-light emission is a promising and economical approach for phosphor-conversion light emitting diodes (pc-LEDs), but traditional single-phase white light emission phosphors are inefficient. Here a white-light-emission phosphor was prepared via a co-precipitation method by doping Sb3+ into lead-free and vacancy-ordered double perovskite Cs 2 ZrCl 6. X-ray diffraction, X-ray photoelectron spectroscopy, and formation energy calculations confirmed that Sb3+ ions replaced the Zr4+sites in the [ZrCl 6 ]2− octahedron. The optical properties of Cs 2 ZrCl 6 :Sb3+ were investigated and compared with those of blank Cs 2 ZrCl 6. The origination of the emission bands was determined according to their fluorescence spectra and decay-time at an approximate temperature of 4 K Sb3+-doped Cs 2 ZrCl 6 exhibited white-light emission with double emission bands at 495 and 622 nm due to the 1P 1 → 1S 0 and 3P 2, 1, 0 → 1S 0 transitions of Sb3+, respectively. The intensity ratios of cyan light (495 nm) and the red light emission bands (622 nm) were tunable by adjusting the Sb3+concentration. The red component increased with increasing Sb3+ concentration in the present experimental range. Moreover, 10% Sb3+-doped Cs 2 ZrCl 6 showed the strongest emission with a photoluminescence quantum yield of approximately 78% under excitation of 333-nm light White LED devices with different correlated color temperatures were achieved by combining 1% or 10% Sb3+-doped Cs 2 ZrCl 6 with a 310-nm ultraviolet chip, suggesting that the synthesized samples have potential applications in white-illumination LEDs. Single-phased white emitting phosphor Cs 2 ZrCl 6 : Sb3+ and corresponding LEDs. [Display omitted] [ABSTRACT FROM AUTHOR]

• Cs 2 NaScCl 6 : Yb3+, Er3+ was prepared through solvothermal method. • UC and DC properties of sample were investigated. • Potential application in anti-counterfeiting was evaluated. At present, most fluorescent anti-counterfeiting technologies on the market are based on single-mode luminescence, which generally have poor anti-counterfeiting capabilities. Thus, developing multi-mode luminescent anti-counterfeiting materials that combine dynamic and static luminescence is a particularly urgent task. In this study, Cs 2 NaScCl 6 : Yb3+, Er3+phosphors were successfully prepared using the solvothermal method. These materials can emit bright green light under 980- or 1550-nm infrared laser irradiation and red light under 365-nm ultraviolet lamp illumination. In addition, by increasing the 980-nm laser power density from 20 to 309 mW/cm2, the luminescence colour can be adjusted from green to yellow, which equips this sample with an outstanding potential for dynamic anti-counterfeiting. Finally, screen printing technology was used to assess the sample's anti-counterfeiting capacity, and the sample was found to be an excellent anti-counterfeiting luminescent material. Stimulus-mode dependent multi-color emitting phosphor Cs 2 NaScCl 6 : Yb3+, Er3+exhibits green emission with the irradiation of 1550 and 980 nm laser and red emission under excitation of 365 nm UV lamp, but yellow emission with the increase of 980 nm laser power density, which present great potential application in anti-counterfeiting field. [Display omitted] [ABSTRACT FROM AUTHOR]

As a new generation of near-infrared (NIR) light source, phosphor-converted NIR light emitting diodes (NIR pc-LEDs) have broad application prospects in biological tissue imaging, night vision and chemical composition analysis. However, most NIR emitting phosphors are still limited to short-wavelength, narrow-band emission and low efficiency. Here, based on the multi-site occupation strategy, the NIR phosphor Mg 2 LaTaO 6 :Cr3+ (MLT:Cr3+) achieves an efficient broadband NIR emission with the full width at half maximum (FWHM) of 203 nm in the range of 600–1300 nm under the excitation of 468 nm blue light. The phosphor MLT:0.01Cr3+ not only exhibits an excellent internal quantum efficiency (IQE) of 85.6 %, but also has good thermal stability and remains about 64.2 % photoluminescence (PL) intensity of room temperature at 423 K. Furthermore, the MLT:0.01Cr3+ phosphor was combined with a blue LED chip to fabricate the NIR pc-LED device, and its potential applications were successfully realized in information encryption, bioimaging and the qualitative or quantitative analysis of mixture of ethanol and water. NIR LED fabricated with broadband emitting phosphor Mg 2 LaTaO 6 :Cr3+ together with its potential application. [Display omitted] [ABSTRACT FROM AUTHOR]

Emission wavelength or color and excitation mode of luminescent materials play the decisive role in their applications of information hiding and anti-counterfeiting. Conventional luminescent anti-counterfeiting materials generally exhibit monochromatic emissions under the excitation of ultraviolet or near-infrared light, which are easily to be imitated or substituted. The development of multicolor and multimodal excitation in one single-phased host was regarded as effective strategy and significant challenges for luminescent anti-counterfeiting materials. As typical lead-free halide double perovskite material Cs2NaBiCl6 not only offers excellent stability and facile synthesis but also provides greater tolerance to rare earth and transitional ions, thus Er3+, Yb3+ and Mn2+ tri-doped Cs 2 NaBiCl 6 was synthesized by co-precipitation method at room temperature in this paper. The efficient green up- and strong orange red down-conversion (UC and DC) emissions were realized through irradiation of 980/1550 nm infrared light and 365 nm near ultraviolet light. The possible UC mechanisms and energy transfer from Er3+ to Mn2+ were also investigated, and some fluorescent security patterns were also designed to demonstrate the potential applications of the present samples in anti-counterfeiting and concealing important information. CNBC: 10% Er3+, 15% Yb3+, 15% Mn2+ exhibits brilliant green and orange emission under the excitation of 980, 1550 and 365 nm light, which present great potential for application in multi-mode anti-counterfeiting. [Display omitted] • The UC phosphor Cs 2 NaBiCl 6 was investigated. • The UC and DC emission color of Cs 2 NaBiCl 6 : Yb3+, Er3+, Mn2+ were discussed. • Potential application as anti-counterfeiting materials was evaluated. [ABSTRACT FROM AUTHOR]

Cr3+ activated near‐infrared (NIR) phosphors are getting unprecedented attention to fabricate the broad band NIR light emitting diodes (NIR‐LEDs) for nondestructive detection, bio‐imaging, and night vision. However, it remains a major challenge to obtain ultrabroadband NIR emitting phosphor with excellent quantum yield (QY). Here, a broadband NIR emitting phosphor Mg7Ga2GeO12:Cr3+ (MGGO: Cr3+) ranging from 600 to 1300 nm with an outstanding QY (93%) and large full width of half maximum (FWHM = 226 nm) is developed, in which the site occupancy tendency of Cr3+ in MGGO host is discussed in detail through combining the structure optimization and the first‐principles theory calculation with luminescent properties at low temperature. After that, the emission intensity of MGGO:Cr3+ is improved through partial substitution of Mg2+ by alkaline‐earth ions Ca2+, Sr2+, or Ba2+, and the luminescence enhancement mechanism is also investigated. Furthermore, the NIR pc‐LED device is fabricated by combining 450 nm blue LED chip with the brightest phosphor MGGO:Cr3+/Ba2+, and its potential applications are evaluated in the field of nondestructive detection, night vision, and bio‐imaging. [ABSTRACT FROM AUTHOR]

With the development of temperature measurement technology, people put forward higher requirements for the accuracy and precision of temperature measurement. However, most of the current luminescent thermometers use a single optical signal for temperature detection, which has a certain range of temperature insensitivity, resulting in inaccurate temperature measurement. Here, an all-inorganic rare-earth halide double perovskite Cs 2 NaErCl 6 : Yb3+ (CNEC: Yb3+) phosphor was synthesized, which not only expressed triple-mode thermometric properties based on thermally coupled levels (TCLs), non-thermally coupled levels (N-TCLs) and lifetime (FL), but also capable of providing self-referencing and high-sensitivity temperature measurements under excitation at 980 nm. Benefiting from the low phonon energy of the matrix, high doping concentration and the excellent internal up-conversion quantum efficiency (UCQY) about 6.52% of optimal composition CNEC: 40%Yb3+, all modes exhibit superior sensitivities, reversibility and thermal resolution under 980 nm irradiation. In addition, a flexible thin film thermometer composed of CNEC: 40%Yb3+ was prepared to realized multi-mode thermal monitoring of local hot spots of electronic components. The excellent three-mode temperature measurement results indicated that CNEC: Yb3+ phosphors have great potential in temperature sensing. [Display omitted] • Halide double perovskite Cs 2 NaErCl 6 : Yb3+ was prepared. • Triple-mode thermometric properties based on thermally coupled levels, non-thermally coupled levels and lifetime were investigated. • Application of the present thermometer was evaluated in monitoring local hot spots of electronic components. [ABSTRACT FROM AUTHOR]

A series of Ba 2 CaW 1- x O 6 : x Mn4+ (BCWO: x Mn4+) far-red emitting phosphors were successfully synthesized via a high-temperature solid-state reaction method. The phase purity and crystal structure were analyzed by X-ray diffraction (XRD) and Rietveld refinement. The luminescent properties and crystal field strength of Mn4+-occupied octahedra [WO 6 ] environment were estimated according to the photoluminescence (PL) and photoluminescence excitation (PLE) spectra. Under near ultraviolet light (n-UV) excitation, far-red light (peaking at 695 nm) was obtained from BCWO: 0.75%Mn4+, which matches well with the absorption band of the phytochrome P FR. In addition, the thermal stability of the phosphor was investigated according to temperature-dependent PL spectra. The Mn4+ doped Ba 2 CaWO 6 phosphor offers good luminescence performance and high thermal stability, and shows great potential for application in plant cultivation LEDs as a suitable far-red emitting phosphor. [Display omitted] • A novel phosphors Ba 2 CaWO 6 : Mn4+ were successfully synthesized by solid-state reaction. • The optimized Ba 2 CaWO 6 : Mn4+ phosphor exhibited far-red light peaked on 695 nm excited by near ultraviolet (n-UV) light. • The crystal field environment of Mn4+ ions were analyzed, and the Mn4+ ions are located in the strong crystal field. • The thermal stability of Ba 2 CaWO 6 : 0.75%Mn4+ phosphor was investigated according to temperature-dependent PL spectra. [ABSTRACT FROM AUTHOR]