Rare-Metal-Free Ultrabroadband Near-Infrared Phosphors.

Trivalent chromium (Cr) is an attractive near-infrared (NIR) emitter, but its ultrabroadband NIR emission is limited to host crystals containing large amounts of rare-metal elements and usually suffers from low internal quantum efficiency (IQE) and poor thermal stability. Here, a class of high-performance, rare-metal-free ultrabroadband NIR phosphors, are reported by revealing that weak-field Cr centers featuring broadband NIR emission with near-unity IQEs are intrinsic, though in trace quantities, to Cr doped MgAlO spinel (MAS) and its derivatives well-known for their narrowband far-red emission. It is shown that such weak-field Cr centers stem from cation inversion ubiquitous in spinel compounds, and their quantity can be increased simply by superstoichiometric AlO/GaO.

Excitation-Selective and Double-Emissive Lead-Free Binary Hybrid Metal Halides for White Light-Emitting Diode and X-Ray Scintillation.

Zero-dimensional (0D) organic metal halides comprising heterogeneous metal cations in single phase can achieve multiple luminous emissions enabling them toward multifunctional light-emitting applications. Herein, A novel single crystal of (CHN)SbMnCl containing two luminescent centers of [SbCl] pentahedrons and [MnCl] tetrahedrons is reported. The large distance between Sb-Sb, Mn-Mn, and Sb-Mn as well as theory calculation indicate negligible interaction between individual centers, thus endowing (CHN)SbMnCl with excitation-dependable and efficient luminescence.

Suppressed Concentration Quenching Brightens Short-Wave Infrared Emitters.

The brightness of doped luminescent materials is usually limited by the ubiquitous concentration quenching phenomenon resulting in an intractable tradeoff between internal quantum efficiency and excitation efficiency. Here, an intrinsic suppression of concentration quenching in sensitized luminescent systems, by exploiting the competitive relationship between light emitters and quenchers in trapping excitation energies from sensitizers, is reported. Although Cr sensitizers and trivalent lanthanide (Ln , Ln = Yb, Nd, and Er) emitters themselves are highly susceptible to concentration quenching, the unprecedentedly high-brightness luminescence of Cr -Ln systems is demonstrated in the short-wave infrared (SWIR) range employing high concentrations of Cr , whereby a record photoelectric efficiency of 23% is achieved for SWIR phosphor-converted light-emitting diodes, which is about twice as high as those previously reported.

Toughening oxide glasses through paracrystallization.

Glasses, unlike crystals, are intrinsically brittle due to the absence of microstructure-controlled toughening, creating fundamental constraints for their technological applications. Consequently, strategies for toughening glasses without compromising their other advantageous properties have been long sought after but elusive. Here we report exceptional toughening in oxide glasses via paracrystallization, using aluminosilicate glass as an example.

Glass-Crystallized Luminescence Translucent Ceramics toward High-Performance Broadband NIR LEDs.

Near-infrared (NIR) phosphor-converted light-emitting diodes (pc-LEDs) are newly emergent broadband light sources for miniaturizing optical systems like spectrometers. However, traditional converters with NIR phosphors encapsulated by organic resins suffer from low external quantum efficiency (EQE), strong thermal quenching as well as low thermal conductivity, thus limiting the device efficiency and output power. Through pressureless crystallization from the designed aluminosilicate glasses, here broadband Near-infrared (NIR) emitting translucent ceramics are developed with high EQE (59.

Low-dose real-time X-ray imaging with nontoxic double perovskite scintillators.

X-rays are widely used in probing inside information nondestructively, enabling broad applications in the medical radiography and electronic industries. X-ray imaging based on emerging lead halide perovskite scintillators has received extensive attention recently. However, the strong self-absorption, relatively low light yield and lead toxicity of these perovskites restrict their practical applications.

Highly efficient phosphor-glass composites by pressureless sintering.

The development of high-power white light-emitting diodes demands highly efficient and stable all-inorganic color converters. In this respect, phosphor-glass/ceramic composites show great promise as they could combine the merits of high quantum efficiency of phosphors and high chemical and thermal stabilities of glass/ceramic matrices. However, strong interfacial reaction between phosphors and matrices at high temperature results in quantum efficiency loss of the embedded phosphors, and traditional solutions rely on high-pressure consolidation techniques.

Efficient Visible-to-NIR Spectral Conversion for Polycrystalline Si Solar Cells and Revisiting the Energy Transfer Mechanism from Ce to Yb in LuAlO Host.

The so-called Shockley-Queisser converting efficiency limit of Si solar cells is believed to be surpassed by using the spectral converter. However, searching for efficient spectral converting materials is still a challenging task. In this paper, efficient visible-to-NIR spectral conversion for polycrystalline Si solar cells has been demonstrated in Ce and Yb codoped LuAlO.

The Inductive Effect of Neighboring Cations in Tuning Luminescence Properties of the Solid Solution Phosphors.

Forming solid solutions through cation substitution is an efficient way to improve the luminescence properties of Ce or Eu activated phosphors and even to develop new ones, which is badly needed for phosphor-converted white LEDs. Here, we report new color tunable solid solution phosphors based on Eu activated KAlBO as a typical case to demonstrate that, besides crystal field splitting of 5d levels, centroid shift and Stokes shift can be dominant in tuning excitation and emission spectra as well as thermal stability of solid solution phosphors, both of which were previously considered to be negligible. Moreover, a general model involving the inductive effect of neighboring cations is proposed to explain the obvious variations in centroid shift and Stokes shift with cation substitution.

Highly Efficient Green-Emitting Phosphors BaYBO with Low Thermal Quenching Due to Fast Energy Transfer from Ce to Tb.

This paper demonstrates a highly thermally stable and efficient green-emitting BaYBO:Ce, Tb phosphor prepared by high-temperature solid-state reaction. The phosphor exhibits a blue emission band of Ce and green emission lines of Tb upon Ce excitation in the near-UV spectral region. The effect of Ce to Tb energy transfer on blue to green emission color tuning and on luminescence thermal stability is studied in the samples codoped with 1% Ce and various concentrations (0-40%) of Tb.

Blue-emitting K2Al2B2O7:Eu(2+) phosphor with high thermal stability and high color purity for near-UV-pumped white light-emitting diodes.

Novel blue-emitting K2Al2B2O7:Eu(2+) (KAB:Eu(2+)) phosphor was synthesized by solid state reaction. The crystal structural and photoluminescence (PL) properties of KAB:Eu(2+) phosphor, as well as its thermal properties of the photoluminescence, were investigated. The KAB:Eu(2+) phosphor exhibits broad excitation spectra ranging from 230 to 420 nm, and an intense asymmetric blue emission band centered at 450 nm under λex = 325 nm.