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Near‐infrared (NIR) phosphors converted light‐emitting diodes (NIR pc‐LEDs) are ideal NIR sources for versatile applications, which imply the practical significance in tailoring the emission of the NIR phosphors to enhance the performance for specific application. Herein, a paradigm of tailoring the emissions in a series of Cr3+‐doped phosphors to match the applications in NIR lighting, detection, and short‐wave infrared sources through combinatorial management of crystal‐field and energy transfer is presented. The emission band largely increases from 84 to 190 nm when the introduction of [MgO6]‐[GeO4] into Y3Ga5O12:0.08Cr3+ forms Y3MgxGa5‐2xGexO12:0.08Cr3+ through the substitution of [GaO6]‐[GaO4]. Such a large increase in width makes it suitable for near‐infrared lighting to near‐infrared detection. Moreover, the Yb3+, Nd3+ and Er3+ are doped to construct energy transfer with Cr3+, broadening the emission infrared region and enhanced thermal stability. An optimized Yb3+ emission dominates Y3Ga5O12:0.4Cr3+,Yb3+ phosphor has excellent thermal stability (129%@423 K) and is suitable for high‐power short‐wave infrared sources. The presented work not only provides a series of well‐performed NIR phosphors, but only lights up the avenue for designing the Cr3+ emission for specific application. [ABSTRACT FROM AUTHOR]

Phosphors with intrinsic white light emission are of great potential in constructing high-quality white LEDs (WLEDs). In this work, we propose the use of energy transfer from Bi3+ to Eu3+ ions for white light emission. A unique Bi3+-activated phosphor LaGdO3 (LGO):Bi3+ was generated using the conventional high-temperature solid-state process. An energy transfer was established by introducing Eu3+ into the phosphor composition. The emission colour of LGO:Bi3+,Eu3+ phosphors changes from cyan to white to orange-red depending on the Bi3+/Eu3+ doping proportion. The energy transfer between the Bi3+ and Eu3+ ions results from the dipole–dipole interaction. The LGO:Bi3+,Eu3+ phosphors were combined with a near-ultraviolet chip to successfully create a single-component WLED device with a colour-rendering index of 92.4. Our work demonstrates the energy transfer as a route for single-component white light emission and makes LGO:Bi3+,Eu3+ phosphors one of the candidate materials for near-ultraviolet lighting. [ABSTRACT FROM AUTHOR]

Broadband near-infrared phosphors have received unprecedented attention in areas such as non-destructive food testing, plant growth light sources, night vision lighting, and medical diagnostics. It is challenging to design phosphors with significant full-width at half-maximum (FWHM) width variations. In this work, Sr3SiAl10O20:Cr3+ (SSAO:Cr3+) has two emission centers and achieves an interesting change of emission peaks from the ultra-narrow band (FWHM = 37 nm) to ultra-wideband (FWHM = 225 nm) with increasing Cr3+ doping concentration. Photoluminescence decay lifetime fitting confirms the existence of energy transfer in two emission centers. The emission intensity and thermal stability of the phosphor after 950 nm were extended by introducing Yb3+ ions. A NIR phosphor-converted LED was fabricated using SSAO:Cr3+,Yb3+ and a 410 nm LED chip, which shows great potential in the fields of night vision illumination, non-destructive monitoring, and information encryption. [ABSTRACT FROM AUTHOR]

In this work, a series of BaSrGd4O8:xBi3+ blue phosphors was synthesized employing the high-temperature solid-state method. Phase purity of the samples was verified by X-ray diffraction and Rietveld refinement. Time-resolved photoluminescence spectra revealed the existence of two distinct Bi sites. Subsequent optimization of dopant types and doping levels in the batch led to an almost twofold increase in quantum efficiency. The introduction of Eu3+ into the phosphors facilitated the construction of an energy transfer pathway. As the concentration of Eu3+ was increased, the emission color changed from blue to purple and finally to red. In addition, the thermal stability and potential applications of the phosphors were extensively investigated. Finally, two WLED devices were successfully fabricated with color rendering indices of 96.27 and 92.18, and correlated color temperatures of 5198 and 2475 K. This underscores the prospective application of these phosphors in the field of high-quality warm WLEDs. [ABSTRACT FROM AUTHOR]

Highly efficient near-infrared (NIR) phosphor converted light emitting diodes (pc-LEDs) can be used in a wide range of applications such as imaging and detection. At present, a few blue LED excitable NIR phosphors have been developed producing an output power of more than 60 mW at a 100 mA input current after pc-LED packing. In this paper, we report a series of Y3AlGa4−xO12:xCr3+ (YAGG:xCr3+) phosphors with emission bands covering 650–900 nm. The Y3AlGa3.9O12:0.1Cr3+ NIR phosphor has high thermal stability, and the integrated emission intensity at 423 K is 92.36% of that at 303 K. Meanwhile, the internal quantum efficiency (IQE) of the phosphors reaches up to 88.43%. Benefiting from the efficient NIR emission of Y3AlGa3.9O12:0.1Cr3+ phosphor, the prepared NIR pc-LEDs fabricated exhibit a high output power of 67.27 mW and an impressive photoelectric conversion efficiency of 22.49% at a driving current of 100 mA, indicating its great potential for pc-LED based applications. [ABSTRACT FROM AUTHOR]

Crystal‐field engineering can obtain targeted emission more effectively, compared with the laborious experimental screening of new hosts. However, there still lack of paradigms for obtaining Ce3+‐doped cyan phosphors by crystal‐field engineering, and the correlation between the emission and the local structure of the Ce3+ ions has rarely been disclosed. Herein, through substituting the K+ in K3‐yRbyGdSi2O7:Ce3+ with Rb+, the emission color changes from yellow‐green to cyan and finally to blue. In addition, the emission intensity and thermal stability greatly improve, as the internal quantum efficiency increases from 39.4% (y = 0) to 83.6% (y = 1.2), and the thermal activation energy increases from 0.25 eV (y = 0) to 0.36 eV (y = 1.2). The optimized luminescent properties have been interpretated from the change in energy level splitting and configuration coordinate of Ce3+, both of which originate from the elongated Ce3+─O2− bonds. Finally, the cyan‐emitting phosphor K1.8R1.2GSO:Ce3+ is applied to bridge the cyan gap in a fabricated white light‐emitting diodes, and the color rendering index is improved from 90.8 to 93.4. This work not only provides an efficient cyan phosphor, but also highlights an avenue for the rational design of phosphors with optimal luminescent properties. [ABSTRACT FROM AUTHOR]

A series of LaCaGaO4:xBi3+,yEu3+ (x = 0.002–0.04, y = 0.02–0.45) phosphors with adjustable emission colors were synthesized by high‐temperature solid‐state reaction. The samples were identified as pure phases by X‐ray diffraction and Rietveld refinement, and the crystal structures were analyzed in detail. The LaCaGaO4:xBi3+ phosphor shows an intense blue emission under near‐ultraviolet excitation, originating from the 3P1 → 1S0 transition. The spectrum analysis reveals that the Bi3+ ions occupy two luminescence centers in the LaCaGaO4 host and that energy transfer can occur. A model of the energy transfer between the Bi3+ and Eu3+ ions was also created and studied in detail. As the Eu3+‐concentration increased, the emission color of the LaCaGaO4:0.005Bi3+,yEu3+ phosphor changed from blue to pink to red. In addition, the fluorescence lifetime, quantum yield, thermal stability, and other properties of the phosphors were characterized and analyzed. Finally, two white light‐emitting diode devices with Ra values of 96.6 and 95 and correlated color temperatures of 4578 and 3324 K were fabricated, indicating the potential of phosphors for warm white lighting applications. [ABSTRACT FROM AUTHOR]

Most commercial phosphor-converted white light-emitting diodes (pc-WLEDs) are manufactured with blue LED chips and yellow-emitting Y3Al5O12:Ce3+ (YAG:Ce3+) garnet phosphor, but the lack of blue-green light in the spectrum results in a low color rendering index (CRI). In this paper, we synthesized Y3ScAl4O12:Ce3+ (YSAG:Ce3+) by replacing Al3+ in YAG:Ce3+ with Sc3+. The introduction of Sc3+ with a larger ionic radius through a cation substitution strategy causes lattice expansion, elongation of the Y–O bond, and ultimately a decrease in Ce3+ 5d level crystal field splitting. As a consequence, the emission spectrum undergoes a blue-shift of 10 nm. Furthermore, the YSAG:Ce3+ phosphor exhibits good thermal stability, and its emission intensity at 423 K is about 58% of that at 303 K. Moreover, the analysis of Eu3+ emission spectra demonstrates that the introduction of Sc3+ resulted in a slight reduction of the dodecahedral lattice symmetry. YSAG:Ce3+ effectively compensates for the lack of the blue-green region, and WLEDs with high color rendering index (90.1), low color temperature (4566 K) and high luminous efficiency (133.59 lm W−1) were prepared using the combination of YSAG:0.08Ce3+, CaAlSiN3:Eu2+ and 450 nm blue chips. These findings indicate that YSAG:Ce3+ garnet phosphor has potential to be used in high quality WLEDs. [ABSTRACT FROM AUTHOR]

Compared with the well-studied energy transfer from Ce3+ to Tb3+, the energy transfer from Eu2+ to Tb3+ has the advantage of high doping concentration of Tb3+, because Eu2+ and Tb3+ tend to occupy different lattice sites. Herein, the energy transfer from Eu2+ to Tb3+ is achieved in the Ca8SrGd(PO4)7 host for an efficient Tb3+ doped green phosphor. The decrease in the lifetime of Eu2+ emission with the increasing Tb3+ concentration reveals the energy transfer from the Eu2+ to Tb3+ ions. Notably, the Tb3+ emission of Ca8SrGd(PO4)7:Eu2+,Tb3+ has the strongest intensity at the unity doping ratio of Tb3+, indicating a non-concentration quenching effect. The absorption efficiency in the near-ultraviolet region was increased from 6% to 75% after Eu2+ was doped into Ca8SrTb(PO4)7, and the emission was enhanced by approximately six times. Consequently, a high quantum efficiency (internal: 63% and external: 51%) was achieved in Ca8SrTb(PO4)7:Eu2+. Finally, a near-ultraviolet chip excited white LED was fabricated by applying the as-prepared Ca8SrTb(PO4)7:Eu2+ as the green phosphor, with a high color rendering index of 93, and a low correlated color temperature of 3728 K. These results indicate that the presented phosphor has potential in lighting applications, providing a new perspective for developing efficient Tb3+ activated phosphors through energy transfer and high doping concentration. [ABSTRACT FROM AUTHOR]

Na2MgScF7 (NMSF) was experimentally obtained for the first time by combining hydrothermal and high-temperature solid-state reactions. X-ray powder diffraction (XRD) combined with Rietveld refinement confirms that NMSF is crystallized in the space group Imma with the cell parameters a = 10.40860(18), b = 7.32804(12) and c = 7.52879(11) Å, α = β = γ = 90° and V = 574.256(24) Å3. Through doping with Tb3+ or Eu3+ ions, downshifting yellow-green or red emission could be achieved in NMSF-based phosphors, respectively. Upconversion emission could also be designed by doping with Yb3+–Er3+, Yb3+–Tm3+, Yb3+–Ho3+ or Er3+. Moreover, the NMSF:Er3+ phosphor exhibited green upconversion emission upon excitation at 980 nm, and it exhibited red emission upon excitation at 1532 nm. Finally, recognizable patterns were obtained under excitation at 254, 365 and 980 nm, indicating that the as-prepared phosphors can be applied to multicolor anti-counterfeiting. Moreover, our synthesis strategy opens up new avenues for the synthesis of novel fluorides. [ABSTRACT FROM AUTHOR]

The rising demand for spectroscopy applications in the fields of information encryption, non-invasive detection and component analysis has attracted extensive attention to achieve high power near-infrared (NIR) light sources. Near-infrared phosphor-converted light emitting diodes (NIR pc-LEDs) are regarded as ideal light sources to meet the current needs due to their advantages of high power, low cost, and portability. However, it remains a huge challenge to design a NIR phosphor with high emission efficiency, superior thermal stability, and broadband emission. Herein, a novel NIR phosphor, Y2CaHfScAl3O12:Cr3+ (YCHSA:Cr3+), is reported from a fundamental study of garnet type inorganic materials. YCHSA:Cr3+ displays an intense broadband NIR emission covering from 650 to 900 nm with a full width at half maximum (FWHM) of 110 nm and good thermal stability (I423K/303K = 76%). Furthermore, we reasonably utilized the energy transfer from the Cr3+ to Yb3+ ions and obtained the YCHSA:0.08Cr3+,0.03Yb3+ phosphor, and achieved performance improvement with a broader NIR emission band (FWHM = 327 nm) as well as better thermal stability (up to I423K/303K = 83%). The excellent performance of NIR pc-LED is crucial for spectroscopy applications. The optimal samples and 450 nm commercial blue chips are packaged into NIR pc-LEDs, and give a high output power of 63.6 mW at a drive current of 100 mA. Finally, the superior performance in information encryption and non-invasive detection is demonstrated. [ABSTRACT FROM AUTHOR]