The role of Pb2+ as a sensitizer for Gd3+–Eu3+ downconversion couple in fluorides

Growth and characterization of thorium-doped calcium fluoride single crystals

We have grown [Formula: see text]Th:CaF[Formula: see text] and [Formula: see text]Th:CaF[Formula: see text] single crystals for investigations on the VUV laser-accessible first nuclear excited state of [Formula: see text]Th, with the aim of building a solid-state nuclear clock. To reach high doping concentrations despite the extreme scarcity (and radioactivity) of [Formula: see text]Th, we have scaled down the crystal volume by a factor 100 compared to established commercial or scientific growth processes. We use the vertical gradient freeze method on 3.2 mm diameter seed single crystals with a 2 mm drilled pocket, filled with a co-precipitated CaF[Formula: see text]:ThF[Formula: see text]:PbF[Formula: see text] powder in order to grow single crystals. Concentrations of [Formula: see text] cm[Formula: see text] have been realized with [Formula: see text]Th with good (> 10%) VUV transmission. However, the intrinsic radioactivity of [Formula: see text]Th drives radio-induced dissociation during growth and radiation damage after solidification. Both lead to a degradation of VUV transmission, currently limiting the [Formula: see text]Th concentration to [Formula: see text] cm[Formula: see text].

Luminescence Performance of BaGd2ZnO5 Microcrystalline Powder Doped with Different Rare Earth Ions

A group of BaGd2ZnO5 microcrystalline powders doped with Sm[Formula: see text], Dy[Formula: see text], Nd[Formula: see text] and Er[Formula: see text]/Yb[Formula: see text] were prepared by high temperature solid phase method, respectively. X-ray diffraction (XRD) analysis confirmed that all the products were pure BaGd2ZnO5 crystals, belonging to orthorhombic system and Pbnm space group. The emission spectra of Sm[Formula: see text], Dy[Formula: see text], Nd[Formula: see text] single-doped and Er[Formula: see text]/Yb[Formula: see text] double-doped samples under specific wavelength excitation were measured. The change of luminescence intensity at strong emission peak with doping concentration of doped ions was studied, and concentration quenching effect was found. The CIE color coordinates of the prepared samples were calculated. The results show that all coordinates doped with Sm[Formula: see text] are located in the orange red region. All coordinates of Dy[Formula: see text] doping samples are located in the yellow light region, but close to the white light region. All coordinates of Nd[Formula: see text] doping sample are located in the blue-green region. The upconversion luminescence of Er[Formula: see text]/Yb[Formula: see text] co-doped sample belongs to yellow light region.

Efficient Luminescence from CsPbBr3 Nanoparticles Embedded in Cs4PbBr6

Cs₄PbBr₆ is regarded as an outstanding luminescent material with good thermal stability and optical performance. However, the mechanism of green emission from Cs₄PbBr₆ has been controversial. Here we show that isolated CsPbBr₃ nanoparticles embedded within a Cs₄PbBr₆ matrix give rise to a "normal" green luminescence while superfluorescence at longer wavelengths is suppressed. High-resolution transmission electron microscopy shows that the embedded CsPbBr₃ nanoparticles are around 3.8 nm in diameter and are well-separated from each other, perhaps by a strain-driven mechanism. This mechanism may enable other efficient luminescent composites to be developed by embedding optically active nanoparticles epitaxially within inert host lattices.

Eu3+ Sensitization via Nonradiative Interparticle Energy Transfer Using Inorganic Nanoparticles

Phosphors have been used successfully for both research and commercial applications for decades. Eu³⁺-doped materials are especially promising, because of their extremely stable, efficient, and narrow red emission lines. Although these emission properties are ideal for lighting applications, weak absorption in the blue spectral range has until now prevented the use of Eu³⁺-based phosphors in applications based on blue light-emitting diodes. Here, we demonstrate a sensitization mechanism of Eu³⁺ based on interparticle Förster resonance energy transfer (IFRET) between lanthanide-doped inorganic nanocrystals (NCs). Compared to co-doping different lanthanides in the same host crystal, IFRET allows an independent choice of host lattices for Eu³⁺ and its sensitizer while potentially greatly reducing metal-to-metal charge transfer quenching. We demonstrate IFRET between NCs, resulting in red Eu³⁺ emission upon blue excitation at 485 nm using LaPO₄:Tb/LaPO₄:Eu and LaPO₄:Tb/YVPO₄:Eu NC mixtures. These findings pave the way toward engineering blue-sensitized line emitters for solid-state lighting applications.

Ultrabroad Photoluminescence and Electroluminescence at New Wavelengths from Doped Organometal Halide Perovskites

Doping of semiconductors by introducing foreign atoms enables their widespread applications in microelectronics and optoelectronics. We show that this strategy can be applied to direct bandgap lead-halide perovskites, leading to the realization of ultrawide photoluminescence (PL) at new wavelengths enabled by doping bismuth (Bi) into lead-halide perovskites. Structural and photophysical characterization reveals that the PL stems from one class of Bi doping-induced optically active center, which is attributed to distorted [PbI6] units coupled with spatially localized bipolarons. Additionally, we find that compositional engineering of these semiconductors can be employed as an additional way to rationally tune the PL properties of doped perovskites. Finally, we accomplished the electroluminescence at cryogenic temperatures by using this system as an emissive layer, marking the first electrically driven devices using Bi-doped photonic materials. Our results suggest that low-cost, earth-abundant, solution-processable Bi-doped perovskite semiconductors could be promising candidate materials for developing optical sources operating at new wavelengths.

Synthesis and photoluminescence of Bi3+,Eu3+ doped CdWO4 phosphors: application of energy level rules of Bi3+ ions

The excitation at 350 nm in CdWO₄:Bi³⁺ was assigned to be the A excitation band of Bi³⁺.