Effect of a-SiCxNy:H Encapsulation on the Stability and Photoluminescence Property of CsPbBr3 Quantum Dots.

The effect of a-SiCxNy:H encapsulation layers, which are prepared using the very-high-frequency plasma-enhanced chemical vapor deposition (VHF-PECVD) technique with SiH4, CH4, and NH3 as the precursors, on the stability and photoluminescence of CsPbBr3 quantum dots (QDs) were investigated in this study. The results show that a-SiCxNy:H encapsulation layers containing a high N content of approximately 50% cause severe PL degradation of CsPbBr3 QDs. However, by reducing the N content in the a-SiCxNy:H layer, the PL degradation of CsPbBr3 QDs can be significantly minimized. As the N content decreases from around 50% to 26%, the dominant phase in the a-SiCxNy:H layer changes from SiNx to SiCxNy. This transition preserves the inherent PL characteristics of CsPbBr3 QDs, while also providing them with long-term stability when exposed to air, high temperatures (205 °C), and UV illumination for over 600 days. This method provided an effective and practical approach to enhance the stability and PL characteristics of CsPbBr3 QD thin films, thus holding potential for future developments in optoelectronic devices.

Multi-Band Emission of Pr3+-Doped Ca3Al2O6 and the Effects of Charge Compensator Ions on Luminescence Properties.

Multi-band emission luminescence materials are of great significance owing to their extensive application in diverse fields. In this research, we successfully prepared a series of Pr3+-doped Ca3Al2O6 multi-band emission phosphors via a high-temperature solid-state method. The phase structure, morphology, luminescence spectra and decay curves were investigated in detail. The Ca3Al2O6:Pr3+ phosphors can absorb blue lights and emit lights in the 450-750 nm region, and typical emission bands are located at 488 nm (blue), 525-550 nm (green), 611-614 nm (red), 648 nm (red) and 733 nm (deep red). The influence of the Pr3+ doping concentration was discussed, and the optimal Pr3+ doping concentration was determined. The impacts of charge compensator ions (Li+, Na+, and K+) on the luminescence of Pr3+ were also investigated, and it was found that all the charge compensator ions contributed positively to the emission intensity. More importantly, the emission intensity of the as-prepared phosphors at 423 K can still maintain 65-70% of that at room temperature, and the potential application for pc-LED was investigated. The interesting results indicate that the prepared phosphors may serve multifunctional and advanced applications.

Triple-Mode Emissions with Invisible Near-Infrared After-Glow from Cr3+ -Doped Zinc Aluminum Germanium Nanoparticles for Advanced Anti-Counterfeiting Applications.

Materials exhibiting persistent luminescence (PersL) have great prospect in optoelectronic and biomedical applications such as optical information storage, bio-imaging, and so on. Unfortunately, PersL materials with multimode emission properties have been rarely reported, although they are expected to be very desirable in multilevel anti-counterfeiting and encryption applications. Herein, Cr3+ -doped zinc aluminum germanium (ZAG:Cr) nanoparticles exhibiting triple-mode emissions are designed and demonstrated. Upon exposure to steady 254 nm UV light, the ZAG:Cr nanoparticles yield steady bluish-white emission. After turning off the UV light, the emission disappears quickly and the mode switches to transient near-infrared (NIR) PersL emission at predominantly 690 nm. The transient NIR PersL emission which arises from Cr3+ is induced by non-equivalent substitution of Ge4+ . After persisting for 50 min, it can be retriggered by 980 nm photons due to the continuous trap depth distribution of ZAG:Cr between 0.65 and 1.07 eV. Inspired by the triple-mode emissions from ZAG:Cr, multifunctional luminescent inks composed of ZAG:Cr nanoparticles are prepared, and high-security labeling and encoding encryption properties are demonstrated. The results indicate that ZAG:Cr nanoparticles have great potential in anti-counterfeiting and encryption applications, and the strategy and concept described here provide insights into the design of advanced anti-counterfeiting materials.

Impacts of 5d electron binding energy and electron-phonon coupling on luminescence of Ce3+ in Li6Y(BO3)3.

In this work, the crystal structure and electronic structure as well as the synchrotron radiation vacuum ultraviolet-ultraviolet-visible (VUV-UV-vis) luminescence properties of Li6Y(BO3)3 (LYBO):Ce3+ phosphors were investigated in detail. The Rietveld refinement and DFT calculation reveal the P21/c monoclinic crystal phase and the direct band gap of the LYBO compound, respectively. Only one kind of Ce3+ 4f-5d transition is resolved in terms of the low temperature VUV-UV excitation, UV-vis emission spectra and luminescence decay curves. Furthermore, by constructing the vacuum referred binding energy (VRBE) scheme and applying the frequency-degenerate vibrational model, the impacts of 5d electron binding energy and electron-phonon coupling on luminescence of Ce3+ in LYBO are analysed. The results show that the Ce3+ emission in LYBO possesses a moderate intrinsic thermal stability. With the increase in concentration, the thermal stability of the emission gets worse due to the possible thermally-activated concentration quenching. In addition, the simulation of Ce3+ emission profile at low temperature reveals that the 4f-5d electronic transitions of Ce3+ ions can be treated to couple with one frequency-degenerate vibrational mode having the effective phonon energy of ∼257 cm-1 with the corresponding Huang-Rhys parameter of ∼6, which indicates a strong electron-phonon interaction of Ce3+ luminescence in the Li6Y(BO3)3 host. Finally, the X-ray excited luminescence spectrum of the LYBO:5%Ce3+ phosphor is measured to check the potential scintillator applications.

Site Occupancies, Luminescence, and Thermometric Properties of LiY9(SiO4)6O2:Ce3+ Phosphors.

In this work, we report the tunable emission properties of Ce3+ in an apatite-type LiY9(SiO4)6O2 compound via adjusting the doping concentration or temperature. The occupancies of Ce3+ ions at two different sites (Wyckoff 6h and 4f sites) in LiY9(SiO4)6O2 have been determined by Rietveld refinements. Two kinds of Ce3+ f-d transitions have been studied in detail and then assigned to certain sites. The effects of temperature and doping concentration on Ce3+ luminescence properties have been systematically investigated. It is found that the Ce3+ ions prefer occupying Wyckoff 6h sites and the energy transfer between Ce3+ at two sites becomes more efficient with an increase in doping concentration. In addition, the charge-transfer vibronic exciton (CTVE) induced by the existence of free oxygen ion plays an important role in the thermal quenching of Ce3+ at 6h sites. Because of the tunable emissions from cyan to blue with increasing temperature, the phosphors LiY9(SiO4)6O2:Ce3+ are endowed with possible thermometric applications.

Luminescence and X-ray absorption studies on 0.5% Ce(3+) doped BaCa2MgSi2O8 phosphor.

0.5% Ce(3+) doped BaCa2MgSi2O8 phosphor was prepared by a conventional solid state reaction method. Luminescence spectra as well as fluorescence decay were monitored in the VUV-UV range. Ce(3+) emissions are assigned to cerium ions on a Ba(2+) site, and the five 4f-5d excitation bands of Ce(3+) were determined at low temperature. The light yield is estimated to be around 10,600 ph MeV(-1) under X-ray excitation. X-ray absorption near-edge structure (XANES) was explored to study the energy transfer efficiency to optical centers from each element in the phosphor; the results show that the contributions to luminescence are not identical for each element.

Luminescence and site occupancies of Eu3+ in La2CaB10O19.

Eu(3+)-activated La2CaB10O19 phosphors with nominal chemical formulae La(2-x)Eu(x)CaB10O19 and La2Ca(1-2x)Eu(x)Na(x)B10O19 were prepared. The luminescence properties under VUV-UV excitation were investigated. Luminescence spectra reveal Eu(3+) ions occupy both Ca(2+) and La(3+) sites in all samples. The O(2-)→ Eu(3+) charge transfer bands (CTBs) and the (5)D0→(7)F0 emissions of Eu(3+) at Ca (2+) site and La(3+) site are identified, respectively. The schematic energy levels for Eu(3+) in two sites were achieved. Luminescence decays of the (5)D0→(7)F0 transitions were measured for both sites.

Unusual method for phenolic hydroxyl bridged lanthanide CPs: syntheses, characterization, one and two photon luminescence.

A "basophilic method" for phenolic hydroxyl bridged lanthanide coordination polymers (CPs) was developed. With this method, eleven CPs with the general formula of [Ln(HL1)L1·H(2)O](n) (Ln = Tb (1), Nd (2), Eu (3), Gd (4), La (5), Er (6), Y (7), H(2)L1 = 4-methyl salicylic acid) and [Ln(HL2)L2·2MeOH](n) (Ln = Eu (8), Tb (9), Gd (10), La (11), H(2)L2 = 3-hydroxy-2-naphthoic acid) were synthesized based on two ligands, and five of them (1-4 and 8) were characterised by X-ray single crystal diffraction. The powder X-ray diffraction patterns (PXRD) of complexes showed that 1-7 are isostructural, 8-11 are isostructural. Furthermore, 1 was characterised by Fourier transform infrared (FT-IR), thermogravimetric analysis (TGA), differential thermal analysis (DTA), elemental analysis (EA), one and two photon luminescence were investigated in detail.

Enhanced emission of Mn2+ via Ce3+ → Mn2+ energy transfer in α-Sr2P2O7.

Mn(2+) doped and Ce(3+)-Mn(2+) co-doped α-Sr(2)P(2)O(7) phosphors were prepared by a traditional high-temperature solid-state reaction route. The UV-vis excitation and emission spectra for all samples were investigated. Luminescence of Mn(2+) is assigned to from two different sites, which is similar to that of Ce(3+). Energy transfer from Ce(3+) to Mn(2+) in co-doped phosphors α-Sr(2)P(2)O(7): 0.03Ce(3+), xMn(2+) and α-Sr(2)P(2)O(7): xCe(3+), 0.1Mn(2+) was investigated by the excitation and emission spectra as well as the luminescence decays. Both Ce(3+)(1) and Ce(3+)(2) can transfer energy to two types of Mn(2+) ions.

Intensive green emission of ZnAl2O4:Mn2+ under vacuum ultraviolet and low-voltage cathode ray excitation.

A series of Zn(1-x)Mn(x)Al(2)O(4) (x=0.001∼0.08) phosphors were synthesized by a traditional solid-state reaction route. Their photoluminescence under vacuum ultraviolet (VUV, energy E>50000 cm(-1), wavelength λ<200 nm) and cathodoluminescence under low-voltage electron beam excitation were evaluated. The luminescence decays were also measured. The intense green emission was observed with a peak at about 510 nm upon 172/147 nm excitation. The luminescence of optimum phosphor Zn(0.99)Mn(0.01)Al(2)O(4) (ZAM) was compared with that of commercial green phosphor Zn(2)SiO(4):Mn(2+) (ZSM). The maximum emission intensity of ZAM is larger than that of ZSM under 172/147 nm and low-voltage electron beam excitation. The values of chromaticity coordinates reveal the phosphors can evidently enlarge the tricolor gamut. The results show that the ZnAl(2)O(4):Mn(2+) phosphors may be considered as candidates for Hg-free lamps, plasma flat backlights, and field emission backlights for liquid crystal displays.

Bright green-emitting, energy transfer and quantum cutting of Ba3Ln(PO4)3: Tb3+ (Ln = La, Gd) under VUV-UV excitation.

Tb3+ doped Ba3Gd(PO4)3 and Ba3La(PO4)3 phosphors were synthesized using the traditional high temperature solid state reaction method. The excitation, emission, and decay spectra were measured at room temperature. Efficient energy transfer (ET) from Gd3+ to Tb3+ exists in Tb3+ doped Ba3Gd(PO4)3, and the ET efficiency increases with the increase of Tb3+ concentration. The visible quantum cutting (QC) via cross relaxation was observed upon exciting low-spin (7D(J)) 5d levels of Tb3+ ions. Ba3Tb(PO4)3 sample shows relatively strong emission intensity in comparison with Zn2SiO4: Mn2+ (ZSM) upon 172 nm excitation, and with a decay time τ(1/10) about 6.4 ms under 351 nm excitation, indicating the potential application of this phosphor for plasma display panels (PDPs) and Hg-free lamps.