Tunable and high-color-rendering white light emissions in full visible spectral range in Ag-aggregates/Sm3+ co-doped germanate glass fluorophors

To achieve a tunable and high-color-rendering white light emission in full visible spectral range, the Ag-aggregates/Sm³⁺ co-doped germanate glass fluorophors were prepared by a melt-quenching method. Under the excitation of different wavelengths, the intense broadband emissions covering full visible spectral range from blue to red were gained in the germanate glasses only containing Ag-aggregates. From the optical spectral analyses, it was found that with increasing the excitation wavelengths, the emission peak position exhibits red-shift. However, the red component in the emission spectra is still of relative lack for realizing high quality white light, therefore Sm³⁺ was introduced as co-dopant to supply the red spectral component. In this way, a series of chroma-tunable and full-color-emitting white lights with color coordinates from (0.26, 0.25) to (0.30, 0.32) were successfully realized based on adjusting the excitation wavelengths and Sm³⁺ concentration. Particularly, the color rendering index (CRI) up to 97.6 was achieved. Furthermore, the luminescence thermal stability of Ag-aggregates/Sm³⁺ co-doped germanate glass fluorophors was investigated based on the Arrhenius model, and the corresponding ΔE values for Ag aggregates and Sm³⁺ emissions were confirmed to be 0.25 and 0.19 eV, respectively. In addition, a temperature sensing model was established based on the luminescence intensity ratio of Ag-aggregates to Sm³⁺, and the thermochromatic property of Ag-aggregates/Sm³⁺ co-doped germanate glasses was also evaluated. It was found that the luminescence color coordinates of Ag-aggregates/Sm³⁺ co-doped glass fluorophors always lie in the white light region when the sample temperature increases from 301 to 693 K, thus indicating that Ag-aggregates/Sm³⁺ co-doped glass fluorophors have potential application in solid-state lighting sources as a single-component white lighting material.     

Photoluminescence of Ag Nanoparticles and Tm3+ Ions in the Bismuth Germanate Glasses for the Blue Light‐Excited W‐LED

Materials containing rare‐earth ions and Ag nanoparticles (NPs) have been widely applied due to prior demonstration of increase in their luminescence properties. Here, Tm³⁺ ions‐doped bismuth germanate glasses were synthesized by a chemical reduction method based on the conventional melting‐quenching technique. The Ag NPs were facilely precipitated in the glass matrix by the chemical reduction method during the annealing process. TEM image shows that the Ag NPs are closely dispersed in the glass matrix. The luminescence properties and energy‐transfer mechanism were systematically investigated by means of absorption, emission, and excitation spectra. Significant enhancements of Tm³⁺ ions emission and a broad emission band centered at 568 nm caused by Ag NPs are observed upon 474‐nm excitation. Our research may illustrate the interactions between Tm³⁺ ions and Ag NPs and provide a simplified way to synthesize the high‐efficiency luminescent materials for the blue light‐excited W‐LEDs.     

Effect of BaF2 Content on Luminescence of Rare‐Earth Ions in Borate and Germanate Glasses

Rare‐earth‐doped oxyfluoride germanate and borate glasses were synthesized and next studied using spectroscopic methods. Influence of fluoride modifier on luminescence properties of rare earths in different glass hosts was examined. The excitation and emission spectra of Pr³⁺ and Er³⁺ ions in the studied glasses were registered. The emission spectra of Pr³⁺ ions in germanate and borate glasses are quite different and depend strongly on the glass host. In samples doped with Er³⁺ ions emission bands located around 1530 nm corresponding to the main ⁴I_13/2→⁴I_15/2 laser transition were registered, independently of the glass host. Quite long‐lived near‐infrared luminescence of Er³⁺ ions was observed for germanate glasses with low BaF₂ content, while in borate glass systems influence of barium fluoride on luminescence lifetimes is not so evident. The Judd–Ofelt calculations were used in order to determine quantum efficiencies of excited states of rare‐earth ions in germanate and borate glasses.     

Quantitative prediction of the glass-forming region and luminescence properties in Tm3+-doped germanate laser glasses

Germanate laser glasses have received much attention as a promising host materials for mid-infrared fiber lasers in recent years because of the outstanding infrared transparency, low phonon energy, and high rare earth solubility of such glasses. However, the development of high-performance germanate laser glasses is usually based on intuition and a trial-and-error method, which can involve long experimental periods and high costs, and thus, this approach is highly inefficient. Recently, with proposals for materials genome engineering, the concept of the “glass genome” has grown of interest to us. Herein, the structures of Tm³⁺-doped germanate laser glasses (BaO–GeO₂ and BaO–La₂O₃–GeO₂) were investigated by Fourier transform infrared spectra (FTIR) and Raman spectra analyses, which revealed that the resulting glass contains similar structural groups to the neighboring congruently melted glassy compounds (NCMGCs) in the composition diagram. What is more, the structure and properties of the resulting laser glasses largely depend on NCMGCs. Then, the glass-forming region, physical properties, and luminescence properties were calculated via the use of NCMGCs in Tm³⁺-doped BaO–GeO₂ binary and BaO–La₂O₃–GeO₂ ternary laser glass systems. The calculated results were in good agreement with the experimental results, thus demonstrating that our approach is practical for predicting the glass-forming region, physical properties, and luminescence properties in Tm³⁺-doped BaO–GeO₂ binary and BaO–La₂O₃–GeO₂ ternary laser glass systems. This work may provide an effective method to develop Tm³⁺-doped germanate laser glasses rapidly and at low cost.     

Synthesis,structure and photoluminescence properties of Tm3+/Dy3+ co-doped borate glass for near-UV white LEDs

Tm³⁺/Dy³⁺ single and co-doped SrO–MgO–B₂O₃ (SMB) glasses were fabricated via the conventional melt-quenching technique. The thermal stability of the host glass was determined by a differential scanning calorimetry (DSC) curve. X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy were measured to characterize the structural properties and vibration features of the as-prepared glasses, respectively. The transmittances of the studied glasses can reach about 90% in the range from 300 to 800 nm. It can be confirmed that Tm³⁺/Dy³⁺ single and co-doped SMB glasses can all be efficiently excited by near-ultraviolet (NUV) light through absorption and photoluminescence excitation spectra. Moreover, the emission spectra and fluorescence decay curves confirmed the existence of energy transfer between Tm³⁺ and Dy³⁺. The Tm³⁺/Dy³⁺ co-doped glasses can both realize tunable emission from blue light to cool white and eventually to warm white light under the excitation of 352, 362, and 365 nm. Furthermore, by using the Inokuti-Hirayama (I–H) model, the energy transfer is testified to be carried out in Tm³⁺-Dy³⁺ clusters through the dipole-dipole (d-d) interaction mechanism. More importantly, the thermal stability of Tm³⁺/Dy³⁺ co-doped SMB glass was demonstrated by temperature-dependent emission spectra. Overall, these results fully indicate that Tm³⁺/Dy³⁺ co-doped SMB glasses have great potential to be used in NUV-based white light-emitting diodes with different requirements.     

Fabrication,tunable fluorescence emission and energy transfer of Tm3+-Dy3+ co-activated P2O5–B2O3–SrO–K2O glasses

A growing demand for white light-emitting diodes (W-LEDs) gives rise to continuous exploration of functional fluorescence glasses. In this paper, Tm³⁺/Dy³⁺ single- and co-doped glasses with composition (in mol%) of 30P₂O₅–10B₂O₃–23SrO–37K₂O were synthesized using the melt-quenching method in air. The physical properties, glass structure, luminescence characteristics and energy transfer mechanism of the glasses were systematically studied. As glass network modifiers, Tm³⁺ and Dy³⁺ ions can densify the glass structure. Excitation wavelength and doping concentration of Tm³⁺/Dy³⁺ ions have a direct impact on the emission intensities of blue and orange light as well as the color coordinate of the as-prepared glasses. A white light very close to standard white light can be obtained under 354 nm excitation when the content of Tm³⁺ and Dy³⁺ is 0.2 mol% and 1.0 mol%, respectively. The results of the emission spectra and decay curves reveal the existence of energy transfer from Tm³⁺ to Dy³⁺. The analytic results based on the Inokuti-Hirayama model indicate that the electrical dipole-dipole interaction may be the main mechanism of energy transfer. Moreover, Tm³⁺/Dy³⁺ co-activated glass phosphor has good thermal stability and chrominance stability and it is a promising candidate for white LEDs and display device.     

Quantum-dots-precipitated rare-earth-doped glass for ultra-broadband mid-infrared emissions

Mid-infrared (MIR) fiber lasers have wide application prospects and great commercial value in the fields of medical operation, remote sensing and military weapon, etc. At present, Tm³⁺-doped glass can obtain broadband luminescence at 2 μm, the introduction of Ho³⁺ or Er³⁺ ions also shows a tunable MIR emission but with limited success. Herein, the rare-earth (RE) doped glass with quantum dots (QDs) precipitation is proposed for achieving ultra-broadband MIR emissions. The types and sizes of QDs are determined by the XRD and TEM, and their optical properties are further characterized by the absorption and emission spectra as well as the lifetime decay curves. It is found that the diameter of the QDs is gradually increased from 1.7 to 5.1 nm by increasing the heat-treated temperature from 490°C to 530°C, respectively. Interestingly, an ultra-broadband emission covering 1400-2600 nm is achieved from the heat-treated glass upon the excitation of 808 nm laser diode as a result of an overlapped emission from Tm³⁺ and PbS. All results suggest that these QDs-precipitated RE-doped glasses have important application prospects in ultra-broadband MIR laser glass, glass fiber, and fiber lasers.     

Blue Upconversion Emission in Germanate Glass Co-Doped with Yb3+/Tm3+ Ions

In the paper, the upconversion luminescence of 70GeO₂–30[Ga₂O₃–BaO–Na₂O] glass system co-doped with Yb³⁺/Tm³⁺ ions was investigated. Strong blue emission at 478 nm corresponding to the transition ¹G₄ → ³H₆ in thulium ions was measured under the excitation of 976-nm diode laser. The dependence of the upconversion emission upon the thulium ion concentration was studied to determine the optimal conditions of energy transfer between energy levels of active dopants. The most effective energy transfer Yb³⁺ → Tm³⁺ was obtained in glass co-doped with molar ratio of dopant 0.7 Yb₂O₃/0.07 Tm₂O₃. The increase in thulium concentration more than 0.07 mol% results in the reverse energy transfer from Tm³⁺ → Yb³⁺, which leads to rapid quenching of the luminescence line at the wavelength 478 nm. In germanate glass co-doped with 0.7Yb₂O₃/0.07Tm₂O₃, the longest lifetime of ¹G₄ level equal 278 μs was achieved. The presented results indicate that elaborated germanate glass co-doped with Yb³⁺/Tm³⁺ ions is a promising material that can be used to produce fiber lasers and superluminescent fiber sources generating radiation in the visible spectrum.     

Effective sensitization of Eu3+ ions on Eu3+/Nd3+ co-doped multicomponent borosilicate glasses for visible and NIR luminescence applications

Eu³⁺/Nd³⁺ co-doped multicomponent borosilicate glasses (ND1E: 10BaO +10ZnF₂+10K₂O +20SiO₂+(49-x) B₂O₃+1Nd₂O₃+xEu₂O₃) were prepared by conventional melting and rapid quench technique to evaluate the effect of Eu³⁺ ions in the Nd³⁺ doped glasses. Thermal stability, structural and spectroscopic characteristics of the ND1E glasses were investigated by using DSC, XRD, FTIR, Optical absorption, excitation and emission measurements. The Judd – Ofelt (JO) analysis is implemented to the absorption spectrum of the prepared glassy matrix in order to identify their potential applicability in lasing devices. Enhancement of ⁷F₀ → ⁵L₆ band (394 nm) with the increasing concentration of Eu³⁺ ion in the Nd³⁺ excitation spectra (λ_emi = 1060 nm) reveals the possibility of obtaining the characteristic fluorescence spectra of Nd³⁺ ion with the typical excitation wavelengths (Nd³⁺ = 584 nm and Eu³⁺ = 394 nm) of both rare earth ions and it is further verified from the emission spectrum. This interesting luminescence effect of showing excellent visible and NIR emission under 394 nm excitation mainly attributes the energy transfer mechanism between the RE³⁺ ions and the reason underlying this effect is discussed in detail with the help of partial energy level diagram. Energy transfer efficiency between the Eu³⁺ and Nd³⁺ ions were evaluated by using the radiative lifetimes of the prepared glasses. Also, a comparison of radiative properties and lasing characteristics of Eu³⁺/Nd³⁺ co-doped glasses with other Nd³⁺ glasses are reported. The emission intensities were characterized using CIE chromaticity diagram and the observed CIE coordinates shows a shift towards reddish – orange region with the increase in Eu³⁺ concentration. The quantum efficiency of the prepared glasses was determined experimentally. The obtained results suggest that the ND1E glassy system can be considered as a potential candidate for visible and NIR luminescence applications.     

Multiphonon assisted upconversion thermal enhancement for optical temperature sensing and high penetration depth

Thermal quenching that the upconversion (UC) luminescence intensities decrease with increasing temperature limits the application of UC luminescence materials in the field of optical temperature sensing. Herein, we report that Tm³⁺/Yb³⁺ doped Gd₂O₃ phosphors achieve thermal enhancement of UC luminescence with the multiphonon assisted process. Significantly, a possible mechanism of Yb³⁺ ions in thermal enhancement and multiphonon assisted UC luminescence process is proposed. Based on the luminescence intensity ratio technique of non-thermally coupled energy levels, research shows that thermal enhancement can effectively improve the optical temperature sensing absolute sensitivity. Owing to the near-infrared excitation and strong near-infrared emission, the UC luminescence of the Gd₂O₃: Tm³⁺/Yb³⁺ phosphors can penetrate 12 mm pork tissue and achieve UC thermal enhancement in 287-314 K after penetrating 6 mm pork tissue, which shows its potential in vivo application. The results not only provide a pathway to realize the thermal enhancement of UC luminescence and the improvement of the temperature sensing sensitivity, but also promote the understanding and utilization of the UC luminescence thermal enhancement.     

Experimental and theoretical studies on NIR luminescence of titanate-germanate glasses doped with Pr3+ and Tm3+ ions

Near-infrared (NIR) luminescence of Pr³⁺ and Tm³⁺ ions in titanate-germanate glasses has been studied for laser and fiber amplifier applications. The effect of the molar ratio GeO₂:TiO₂ (from 5:1 to 1:5) on spectroscopic properties of glass systems was studied by absorption, luminescence measurements, and theoretical calculations using the Judd–Ofelt theory. It was found that independent of the TiO₂ concentration, intense NIR emissions at 1.5 and 1.8 μm were observed for glasses doped with Pr³⁺ and Tm³⁺ ions, respectively. Moreover, several spectroscopic and NIR laser parameters for Pr³⁺ and Tm³⁺ ions, such as emission bandwidth, stimulated emission cross-section, quantum efficiency, gain bandwidth, and figure of merit, were determined. The results were discussed in detail and compared to the different laser glasses. Systematic investigations indicate that Pr³⁺-doped system with GeO₂:TiO₂ = 2:1 and Tm³⁺-doped glass with GeO₂:TiO₂ = 1:2 present profit laser parameters and could be successfully applied to NIR lasers and broadband optical amplifiers.     

Improved broadband near-infrared luminescence in Nd3+/Tm3+ co-doping tellurite glass with Ag NPs

The near-infrared (NIR) luminescence in S+E+O bands of tellurite glasses doped with Nd³⁺/Tm³⁺ and Ag nanoparticles (NPs) was investigated. The tellurite glasses were prepared by melt-quenching and heat-treated techniques. Under the excitation of 808 nm laser, Nd³⁺/Tm³⁺ doped tellurite glasses produced three NIR luminescence bands of 1.33, 1.47 and 1.85 μm, originating from Nd³⁺:⁴F_3/2→⁴I_13/2, Tm³⁺:³H₄→³F₄ and Tm³⁺:³F₄→³H₆ transitions respectively. Interestingly, a broadband luminescence spectrum ranging from 1280 to 1550 nm with the FWHM (full width at half maximum) about 201 nm was obtained due to the overlapping of the first two NIR bands. Further, the peak intensity of this broadband luminescence was increased by 75% after the introduction of Ag NPs with diameter in 10–20 nm. The analysis of fluorescence decay shows that compared with the enhanced local electric field, the energy transfer from Ag species to Nd³⁺ and Tm³⁺ ions plays a major role in luminescence enhancement. The findings in this work indicate that tellurite glass co-doped with Nd³⁺/Tm³⁺ and Ag NPs is a potential gain material applied in the S+E+O-band photonic devices.     

Realization of pure red emission from energy transfer in the Er3+–Tm3+ system under 1550 nm excitation

NaY(WO₄)₂ is one of the excellent host materials for high-efficient upconversion luminescence, but it is still challenging to obtain red emission via lanthanide doping. In this work, pure red emission was achieved in the heavily-Er³⁺-doped NaY(WO₄)₂ by using a 1550 nm laser diode and introducing mediator Tm³⁺ ions in the lattice. On basis of the analysis of steady-state and transient-state luminescence properties related to dopant concentration and excitation wavelength, all possible red emission mechanisms were discussed. Finally, it has been demonstrated that the high-purity red emission was due to the several energy transfer processes between Er³⁺ and Tm³⁺. Our results provide a convenient pathway to investigate the upconversion luminescence mechanisms.     

Surface modification and fabrication of white-light-emitting Tm3+/CdS quantum dots co-doped glass fibers

Due to the widely tunable band gap and broadband excitation, CdS quantum dots (QDs) show great promise for yellow-light luminescence center in white-light-emitting devices. The light intensity of the CdS QD-doped glass was enhanced by doping the Tm³⁺ ions due to the higher absorption rate. The influence of Tm³⁺ ions on the surface structure of CdS QDs was enormous according to the first-principles calculations. Doping Tm³⁺ ions change the surface state of CdS QDs, which will fix the QDs emission peaks and enhance the luminescence of CdS QDs at a lower heat-treatment temperature. White-light emission was obtained by tuning the relative concentration between Tm³⁺/CdS QDs. However, there is a fundamental challenge to fabricate QD-doped glass fibers by rod-in-tube method since uncontrollable QDs crystallization is hard to avoid. Herein, a white-light-emitting borosilicate glass fiber was fabricated by the “melt-in-tube” method using a special designed Tm³⁺/CdS QDs co-doped borosilicate glass with low-melting temperature as fiber core. After heat treatment, ideal white-light emission was observed from the fiber under excitation at single wavelength (359 nm). This finding indicates that Tm³⁺/CdS QDs co-doped glass fiber with white-light-emitting devices has potential application as gain medium of white-light-emitting sources and fiber lasers.     

Ce3+‐ and Dy3+‐Doped Oxyfluoride Borosilicate Glasses with Near White Luminescence

A series of Ce³⁺/Dy³⁺‐doped oxyfluoride borosilicate glasses prepared by melt‐quenching method are investigated for light‐emitting diodes applications. These glasses are studied via X‐ray diffraction (XRD), optical absorption, photoluminescence (PL), color coordinate, and Fourier transform infrared (FT‐IR) spectra. We find that the absorption and emission bands of Ce³⁺ ions move to the longer wavelengths with increasing Ce³⁺ concentrations and decreasing B₂O₃ and Al₂O₃ contents in the glass compositions. We also discover the emission behavior of Ce³⁺ ions is dependent on the excitation wavelengths. The glass structure variations with changing glass compositions are examined using the FT‐IR spectra. The influence of glass network structure on the luminescence of Ce³⁺/Dy³⁺ codoped glasses is studied. Furthermore, the near‐ideal white light emission (color coordinate x = 0.32, y = 0.32) from the Ce³⁺/Dy³⁺ codoped glasses excited at 350 nm UV light is realized.     

Multicolor upconversion emission and highly optical temperature sensing based on lanthanide-doped double perovskite Sr2LaNbO6 phosphors

Here we adopt trivalent lanthanide (Ln³⁺ = Er³⁺, Er³⁺/Ho³⁺, and Yb³⁺/Tm³⁺) doped Sr₂LaNbO₆ (SLNO) as novel upconversion luminescence (UCL) materials for achieving UCL and optical temperature sensing under 980 nm excitation. Specifically, Er³⁺ single doped Sr₂LaNbO₆ phosphors present bright high-purity green emission under the 980 nm excitation. While co-doping with the Ho³⁺ ions, the component of red emission from Er³⁺ ions increases significantly and sample show a remarkable enhancement of luminescent intensity relative to SLNO:Er³⁺ sample. The above-mentioned phosphors and Yb³⁺/Tm³⁺ co-doped phosphor (blue emission) successfully achieve high-purity trichromatic UCL and mixed white light output in the same host. Furthermore, the temperature sensing performance of the SLNO:Er³⁺/Ho³⁺ phosphor based on the fluorescence intensity ratio (FIR) is systematically studied for the first time. The temperature sensing based on the non-thermal coupling levels (NTCLs) exhibit higher sensitivity than that based on the thermal coupling levels (TCLs). The maximum absolute and relative sensitivity for ⁴F_9/2/⁴I_9/2 NTCLs reach 0.16803 K^?1 at 427 K and 0.01591 K^?1 at 641 K, respectively. Interestingly, NIR emission of ⁴I_9/2 → ⁴I_15/2 transition presents a thermal enhancement, while visible emissions show thermal quenching. These results indicate that the Ln³⁺ doped Sr₂LaNbO₆ UCL phosphors have potential applications in the fields of non-contact temperature sensors, full-color displays, and anti-counterfeiting.     

Intense red emission via energy transfer from (Ce3+/Eu3+):P2O5+NaF+CaF2+AlF3 glasses for warm light sources

Europium (Eu³⁺)-doped fluorophosphate (PNCA:P₂O₅+NaF + CaF₂+AlF₃) glasses with the addition of cerium (Ce³⁺) ions were fabricated by the melt-quenching technique to know their ability for the bright red (615 nm) luminescence. The emission (PL) and excitation (PLE) spectra, decay curve measurements as well as energy transfer (ET) process of Ce³⁺→ Eu³⁺ were studied in detail. An excitation spectrum related to the ⁷F₀→ ⁵D₂ level of Eu³⁺ is used to estimate the phonon energy (1121 cm^?1) of the title glass host. Under ultraviolet (UV) irradiation of 299 nm, the PL spectra of (Ce³⁺/Eu³⁺):PNCA glasses show intense red emission at 615 nm whereas the lifetime decrease with respect to increase of Eu³⁺ that could support the observed efficient ET from Ce³⁺ to Eu³⁺. The ET:Ce³⁺ →Eu³⁺ via quadrupole-quadrupole process was confirmed by Reisfeld's approximation and Dexter's ET formula. The ET efficiency (η_ET) and critical distance (R_c) were also calculated. Interestingly, the (Ce³⁺/Eu³⁺):PNCA glasses showed intense red light emission with low correlated color temperatures and the corresponding color purity reached as great as 99%, indicating its potentiality as a red component for warm light sources.     

Multifunctional α-NaYbF4:Tm3+ nanocrystals with intense ultraviolet self-sensitized upconversion luminescence and highly efficient optical heating

Lanthanide-doped upconversion photoluminescent nanoparticles with unique anti-Stokes spectroscopic properties excel in many fields of application. Ytterbium-based self-sensitized fluorides with rich Yb³⁺ possess higher absorption efficiency of incident near infrared laser, and are more favorable for photoluminescence or optical heating applications. In this work, α-NaYbF₄:Tm³⁺ crystalline nanoparticles are synthesized, which exhibit intense ultraviolet self-sensitized upconversion photoluminescence and highly efficient optical heating capability under 980 nm laser excitation. NaYbF₄:Tm³⁺ nanocrystals emit multi-band luminescence with emission peaks located in the ultraviolet, blue and red spectral regions. The energy transfer mechanism and electronic transition pathways for the Upconversion luminescence are investigated based on the energy level scheme, and are further confirmed by luminescent dynamic analysis. Due to cross-relaxations between Tm³⁺ and energy back transfer from Tm³⁺ to Yb³⁺ processes, the NaYbF₄: 1 mol% Tm³⁺ nanoparticles possess the highest luminescence intensity. The luminescent dynamic characteristics, such as decay time and rise time, vary with Tm³⁺ doping concentrations. Highly efficient optical heating effect is observed in the NaYbF₄:Tm³⁺ nanoparticles with slope efficiency of photothermal conversion for 10 s laser irradiation is as high as 100.48 °C/W.     

Photoluminescence characteristics and mechanism of SrAl2O4 co-doped with Eu3+ and Cu2+

SrAl₂O₄ co-doped with Cu²⁺ and Eu³⁺ was prepared at high temperature in a weakly oxidizing atmosphere by solid states reaction. X-ray diffraction (XRD) pattern of the sample shows that the doped sample exhibits SrAl₂O₄ crystalline phase. No characteristic peaks of dopant have been observed in XRD pattern of doped sample. The excitation and emission spectra of CuEu:SrAl₂O₄, Eu:SrAl₂O₄, Cu:SrAl₂O₄ samples consist of many sharp peaks. The excitation and emission spectra of the SrAl₂O₄ sample co-doped with Cu²⁺ and Eu³⁺ are significantly different from those of Eu:SrAl₂O₄ and Cu:SrAl₂O₄ samples. The novel photoluminescence (PL) characteristic of the co-doped sample is attributed to the composite luminescence of Cu²⁺ and Eu³⁺ ions in SrAl₂O₄ matrix.     

Tunable Mission and Trichromatic White‐Emitting in Oxyfluoride Glasses by Utilization of Cu+ Ions as Multiple Energy‐Transfer Creators

A series of copper species, Tb³⁺, Mn²⁺ single‐ and co‐doped oxyfluoride glasses were synthesized by a melt‐quenching method. The photoluminescence properties of the glasses containing copper species were demonstrated. Results indicate that the blue‐green emission band peaking at 440 nm was observed, which was ascribed to the photoluminescence of Cu⁺ ions rather than the emissions of Cu²⁺ cations or Cu nano‐particles (Cu NPs) induced by local field effect (LFE) enhancement through surface plasmon resonance (SPR). The interaction mechanisms between Cu⁺ and Tb³⁺/Mn²⁺ have been systematically investigated, and significant enhancement of Cu⁺ emission and the energy‐transfer (ET) efficiencies of Cu⁺→Tb³⁺ and Cu⁺→Mn²⁺ were observed in glasses doped with SnO reducing agent. Furthermore, a wide‐range‐tunable emission and ideal white‐light fluorescence were realized in Cu⁺/Tb³⁺/Mn²⁺‐coactivated glasses by utilization of Cu⁺ cations as dual ET contributors from deep‐UV‐source to multiactivators. Our research further extends the understanding of the interactions between Cu⁺ and Tb³⁺/Mn²⁺ in amorphous materials.