An efficient and thermally stable Cr3+-activated Y2GdSc2Al2GaO12 garnet phosphor for NIR spectroscopy applications.

Near-infrared (NIR) spectroscopy realized by an NIR phosphor-converted light-emitting diode (pc-LED) as a light source has aroused considerable interest due to its numerous merits and widespread application scenarios. Nevertheless, developing NIR emitting phosphors with high performance is still the top priority. Here, we report a new Y2GdSc2Al2GaO12:Cr3+ (YGSAG:Cr3+) garnet phosphor, which demonstrates a broadband emission peaking at 754 nm with a full width at half maximum (FWHM) of around 120 nm in the range of 650-1200 nm. The YGSAG:0.08Cr3+ sample irradiated by blue light exhibits the most intense emission intensity, leading to a high absorption efficiency of 49.54%. In addition, compared with room temperature, the integrated PL intensity of the sample can still be maintained at 90.97% at 423 K. Benefitting from the outstanding optical properties, the as-manufactured NIR pc-LED device driven by a 100 mA current represents a high NIR output power of 35.14 mW and a photoelectric efficiency of 12.51%. These results verify that the as-synthesized YGSAG:Cr3+ phosphor possesses great potential for the applications of NIR spectroscopy.

Near-Infrared LuCa2ScZrGa2GeO12:Cr3+ Garnet Phosphor with Ultra-broadband Emission for NIR LED Applications.

Near-infrared phosphor-converted light-emitting diodes (NIR pc-LEDs), as a new generation of NIR lighting sources, have wide prospects in the areas of food analysis and biological and night vision imaging. Nevertheless, NIR phosphors are still limited by short-wave and narrowband emissions as well as low efficiency. Herein, a series of NIR phosphors, LuCa2ScZrGa2GeO12:Cr3+ (LCSZGG:Cr3+), with broadband emissions have been developed and first reported. At 456 nm excitation, the optimized LCSZGG:0.005Cr3+ phosphor represents an ultra-broadband emission within the range of 650-1100 nm, peaking near 815 nm with a full width at half maximum of 166 nm. Furthermore, the LCSZGG:0.005Cr3+ phosphor possesses good internal quantum efficiency of 68.75%, and its integrated emission intensity at 423 K still retains about 64.17% of that at room temperature. By combining the optimized sample with a blue chip, a NIR pc-LED device is fabricated, which has an excellent NIR output power of 37.88 mW with an NIR photoelectric conversion efficiency of 12.44% under a 100 mA driving current. The aforementioned results demonstrate that these LCSZGG:Cr3+ broadband NIR phosphors are expected as NIR light sources.

Recent Advances in Multi-Site Luminescent Materials: Design, Identification and Regulation.

The development of novel phosphor materials with excellent performance and modification of their photoluminescence to meet the higher requirements for applications are the essential research subjects for luminescent materials. Multi-site luminescent materials with crystallographic sites for the activator ions that broaden the tunable range of luminescent spectra and even enhance the luminescent performance have attracted significant attention in the pursuit of high-quality luminescence for white light-emitting diodes. Here, we summarize multi-site luminescence characteristics based on the different kinds of host and activator ions, introduce the identifications of multi-site activator ions via optical analysis, provide a structural analysis and theoretical calculation methods, and introduce the regulation strategies and advance applications of multi-site phosphors. The review reveals the relationship between crystal structure and luminescent properties and discusses future opportunities for multi-site phosphors. This will provide guidance for the design and development of luminescent materials or other materials science.

Luminescence properties and energy transfer investigations of Ce3+ and Tb3+ co-doped NaCaGaSi2O7 phosphors.

The NaCaGaSi2O7:Ce3+、NaCaGaSi2O7:Tb3+ and NaCaGaSi2O7:Ce3+/Tb3+ phosphors were synthesized under a weak reducing atmosphere by the traditional high temperature solid state reaction method. The synthesized phosphors were characterized by X-ray diffraction (XRD), fluorescent decay times, photoluminescence (PL) emission and excitation spectra including temperature-dependent PL properties. The effects of Ce3+ singly doped and Ce3+/Tb3+ co-doped concentrations on the structure, luminescence properties and energy transfer of NaCaGaSi2O7 phosphors were studied in detail. The results indicated that the energy transfers between Ce3+ and Tb3+ in the host occurred mainly via a dipole-dipole mechanism, and the critical distances of the ion pairs (Rc) were calculated by the quenching concentration method and spectral overlap method. The Ce3+ emission intensity and decay lifetimes decrease with the raise of Tb3+ concentration in NaCaGaSi2O7:Ce3+/Tb3+ samples. The above results indicate that NaCaGaSi2O7:Ce3+/Tb3+ can be a candidate as a host material for solid-state lighting and display fields.