Co-doped Phosphors Research Articles

Improvement in luminescence of thermally stable CaMoO4:Tb3+ green phosphor by Bi3+ ions

The growing optoelectronic industries have prompted researchers to develop a single-component green phosphor for diverse applicability. It is well known that Tb3+ doped phosphors emit green light due to strong 5D4→7F5 transition. The green emission of Tb3+ ion can be enhanced by using sensitizers such as Bi3+ ion, which creates intermediate energy levels between the host and Tb3+, thereby, achieving efficient energy transfer between the host and Tb3+. In this article, we have reported a substantial improvement in the green emission of Tb3+ doped CaMoO4 by Bi3+ co-doping. The phosphors have been successfully prepared via a lucrative self-combustion process. The XRD patterns reveal an impurity-free tetragonal crystalline structure of all the phosphors. The Tb3+ doped CaMoO4 gives three major emissions at 489 nm, 544 nm and 621 nm corresponding to the Tb3+ transitions from 5D4 to 7F6, 7F5, and 7F3, respectively. The maximum emission has been achieved for 5% Tb3+ doped CaMoO4, which is further enhanced by 47% via co-doping of Bi3+. The improvement in emission intensity for Bi3+ co-doped phosphors is attributed to improved crystalline nature and transfer of energy from Bi3+ to Tb3+ levels. The energy transfer process from [MoO4]2- to Bi3+ and Tb3+ is explained in detail and maximum improvement is obtained upon co-doping of 4% Bi3+ ions. The incorporation of Bi3+ ions also results in shifting of CIE coordinates and color purity towards green color. The activation energy required for the thermal quenching is 0.25 eV, much better than already reported green phosphors. There is no change in the CIE coordinates of the overall emission with temperature indicating the better emission color stability of the phosphor. Hence with optimum concentration of Bi3+ and Tb3+ ion in CaMoO4 they can be used as potential green emitting phosphors.

Preparation and luminescence properties of Ba2P2O7:Dy3+, Ce3+ phosphors

In this paper, Ba2-x-yP2O7:xDy3+,yCe3+ phosphors are synthesized by calcining the precursor via chemical co-precipitation. The phase structure, excitation and emission spectra, thermal stability, the chromatic performance of phosphors, and energy transfer from Ce3+ to Dy3+ are studied and discussed. The results indicate the samples keep a stable crystal structure as a high-temperature σ-Ba2P2O7 phase with two different coordination of Ba2+ sites. Ba2P2O7:Dy3+ phosphors can be effectively excited by 349 nm n-UV light and emit 485 nm blue light and a relatively stronger yellow light peaking at 575 nm, corresponding to 4F9/2→6H15/2 and 4F9/2→6H13/2 transitions of Dy3+, implying that Dy3+ mainly occupies the non-inversion symmetric sites. By contrast, Ba2P2O7:Ce3+ phosphors exhibit a broadband of excitation peaking at 312 nm, and two symmetrical emission peaks at 336 nm and 359 nm from 5d1→4F5/2 and 5d1→4F7/2 transitions of Ce3+, showing Ce3+ should merely be presumed to occupy Ba1 site. After Dy3+ and Ce3+ are co-doped, Ba2P2O7:Dy3+, Ce3+ phosphors exhibit the enhanced characteristic blue and yellow emission of Dy3+ with nearly equal intensity under excitation at 323 nm, meaning Ce3+ co-doping increases the symmetry of Dy3+ site as well as the sensitizer. Simultaneously, energy transfer from Dy3+ to Ce3+ is found and discussed. The thermal stability of co-doped phosphors was characterized and briefly analyzed. The color coordinates of Ba2P2O7:Dy3+ phosphors fall in the yellow-green region near the white light, while the emission moves towards the blue-green region after the Ce3+ is co-doped.

Broadband-sensitive up-conversion in Ni2+/Er3+ co-doped Gd2MgTiO6

Ni2+ doped and Ni2+/Er3+ co-doped Gd2MgTiO6 (GMT) phosphors have been synthesized by conventional high-temperature solid-state reaction method. First-principles calculation and X-ray diffraction analysis proves that Ni2+ ions occupy the Mg2+ sites in the Gd2MgTiO6 matrix at low Ni2+ doping concentration and begin to occupy Ti4+ sites at high Ni2+ doping concentration. The near infrared emissions of Ni2+ ions occupying Mg2+ and Ti4+ sites peak at 1344 nm and 1412 nm, respectively, forming a broad near infrared emission band from 1100 nm to 1700 nm. It is found that Ni2+/Er3+ co-doped Gd2MgTiO6 phosphor is capable to up-convert near infrared photons in the wavelength range of 870–1700 nm to visible 532 nm, 555 nm and 666 nm emission, caused by the energy transfer sensitization process from Ni2+ to Er3+. The Ni2+ and Er3+ concentration dependent up-conversion properties have been investigated and it is found that the Gd2MgTiO6: 2%Ni2+/5%Er3+ phosphor shows the strongest up-conversion emission, in which the energy transfer efficiencies from the Ni2+ ions occupying Mg2+ and Ti4+ sites to the Er3+ ions are 81.5% and 79.3%, respectively. The Gd2MgTiO6: 2%Ni2+/5%Er3+ phosphor shows yellow emission under the irradiation of 1342 nm and 1550 nm lasers, and green and orange-red emissions under the irradiation of 980 nm and 1064 nm laser, respectively. The broad band excitability and multi-color up-conversion performance of the Ni2+/Er3+ co-doped Gd2MgTiO6 phosphor suggest that it has wide application prospect in anti-counterfeiting, solar cell efficiency enhancement, infrared detection and so on.

Tunable luminescence and efficient energy transfer investigation of a borosilicate phosphor KBSi2O6: Bi3+, Eu3+ with hypersensitive thermal quenching

Energy transfer between Bi3+ and Eu3+ has undergone substantial research but Bi3+ and Eu3+ co-doped luminescent materials with high energy transfer efficiency for temperature sensing are rarely investigated until now. Herein, Eu3+ and Bi3+ co-doped KBSi2O6 phosphors were successfully synthesized by solid-state reaction method. The phase purity structure as well as the element distribution were carefully investigated through X-ray diffraction structural refinement and energy dispersive spectrometer analysis. The characteristic luminescence property and luminescence kinetics of KBSi2O6: Bi3+, Eu3+ were investigated. By the large spectra overlap between the emission spectrum of Bi3+ and excitation spectrum of Eu3+, the energy transfer from Bi3+ to Eu3+ can be inferred. The corresponding decrease of the emission intensity and decay time of Bi3+ in KBSi2O6: Bi3+, Eu3+ provided direct evidence for the effective energy transfer from Bi3+ to Eu3+. The interaction and energy transfer mechanism between Bi3+ and Eu3+ ions were also studied. By increasing the Eu3+ concentration in KBSi2O6: Bi3+, Eu3+, the color-tunable emission from blue to red can be realized. KBSi2O6: Bi3+, Eu3+ shows hypersensitive thermal quenching behavior and the maximum absolute sensitivity (Sa) and relative sensitivity (Sr) are determined to be 1.87 %K−1 and 2.895 %K−1, respectively. All of the above results imply that KBSi2O6: Bi3+, Eu3+ phosphor can be a color-tunable phosphor for optical temperature sensing.

Energy transfer in Sm3+/Eu3+ doped Li6Gd(BO3)3 orange-red phosphor

Sm3+ and Sm3+/Eu3+ doped Li6Gd(BO3)3 (LGBO) powders were prepared by solid-state reaction. The microstructure, luminescent characteristics, energy transfer and fluorescence lifetimes were studied. Gd3+ can absorb energy and transfer it to Sm3+ under 278 nm excitation, which increases the luminescent intensity of Sm3+ at 567, 611 and 649 nm. Under 405 nm excitation, the 4G5/2-6H5/2 transition belonging to Sm3+ and the 5D0-7F2 transition belonging to Eu3+ appear in the emission spectra of Sm3+/Eu3+ co-doped LGBO phosphors, glowing yellow-orange and red light, respectively. The mechanism behind the energy transfer was analyzed, and the energy transfer efficiency was calculated to be 31.2% when the Sm3+ concentration reached 4mol%. The LGBO:Sm3+/Eu3+ phosphors have prospective applications in solid-state lighting, display devices, bio-imaging, etc.

Dual luminescent peaks, energy transfer and temperature sensor properties of a new Eu2+/Mn2+ co-doped phosphor

Dual luminescent peaks, energy transfer and temperature sensor properties of a new Eu2+/Mn2+ co-doped phosphor

Tunable photoluminescence properties and non-contact thermometry of Bi3+, Sm3+ co-doped YVO4 phosphors

Tunable photoluminescence properties and non-contact thermometry of Bi3+, Sm3+ co-doped YVO4 phosphors

Rare-earth and transition metal ion single-/co-doped double-perovskite tantalate phosphors: Validation of suitability for versatile applications

Novel rare-earth (RE; e.g., europium (Eu³⁺), samarium (Sm³⁺), and praseodymium (Pr³⁺)) and transition metal (TM⁴⁺; e.g., manganese (Mn⁴⁺)) ion single-/co-doped double-perovskite Ca₂InTaO₆ (CITO) phosphors were prepared and investigated with respect to their crystal structure and photoluminescence (PL) properties. Among them, the CITO:Eu³⁺ phosphors were found to exhibit an ultra-high internal PL quantum yield (89.1%) and good thermal stability (78.7% at 423 K relative to the initial value at 303 K). As such, the corresponding packaged white light-emitting diode (LED) was able to display a remarkable color rendering index (CRI; = 91.51@10 mA). Besides, the potential in applications of anti-counterfeiting fields and a novel LED structure based on flexible phosphor-converted films was also studied. Moreover, due to their different thermal quenching, trivalent lanthanide (Ln³⁺)/Mn⁴⁺ co-doped CITO phosphors were designed for optical thermometry based on the luminescence intensity ratio (LIR) between different 4f transitions of various Ln³⁺ ions and ²E_g → ⁴A_2g (Mn⁴⁺) transition. Particularly, the LIR between the ⁴G_5/2 → ⁶H_9/2 and ²E_g → ⁴A_2g peaks of the CITO activated with 5 mol% Sm³⁺ and 0.3 mol% Mn⁴⁺ exhibited the most excellent relative sensitivity (<i>S</i>_r; = 3.80 %·K⁻¹) with beneficial temperature uncertainty of 0.0648 K. Overall, these results are of significance to offer valuable databases for constructing multifunctional high-performance optical platforms using single-/co-doped double-perovskite tantalates.

Trap‐Dependent Optical/Thermal Stimulated Luminescence of Gallate Phosphors Charged by UV–visible–NIR light for Multiplexed Data Storage

AbstractUV‐charged optical stimulated single‐band phosphors are being used for single‐level optical data storage because of their ability to easily write/read information by light. In contrast, UV–visible–NIR rechargeable optical stimulated double‐band phosphor is urgently necessary for multiplexed high‐throughput optical data storage. Here, the authors design and synthesize Mn2+,Cr3+ co‐doped zinc gallate storage persistent phosphor that exhibits strong red‐green bicolor persistent luminescence (PersL). Besides the traditional ultraviolet charging, the phosphor can be effectively and repeatedly charged by using visible and NIR light by one‐ or two‐photon process. Interestingly, red and green PersL exhibit the opposite temperature dependence, which is extremely important for multilevel information storage. The mechanism of temperature‐dependent PersL intensity based on different trap types and filling approaches for the double luminescence centers is proposed. The phosphor promises a sophisticated application in optical data storage of wavelength multiplexing.

A novel Mn4+ -activated far-red Sr2 MgWO6 phosphor: synthesis, luminescence enhancement, and application prospect.

A novel far-red emitting phosphor Sr2 MgWO6 : Mn4+ was fabricated using high-temperature solid-state reaction. X-ray diffraction patterns, scanning electron microscopy images, and photoluminescence excitation and photoluminescence spectra for this phosphor were analyzed in detail. The analysis revealed that its emission ranged from 600 to 800 nm and peaked at 699 nm, which was attributed to the 2 Eg →4 A2g transition of Mn4+ under 314 nm excitation. Moreover, we introduced rare-earth Yb3+ ions into the Sr2 MgWO6 :Mn4+ to improve its far-red emitting intensity. The photoluminescence (PL) intensity of the Yb3+ co-doped phosphor was three times higher than that of the single-doped phosphor. Therefore charge compensation is an efficient approach to improving PL intensity. The phosphor emitted a far-red light that resembled the pigments essential for plant growth in terms of the absorption spectrum. Therefore, the obtained phosphor, Sr2 MgWO6 :0.006Mn4+ ,0.2Yb3+ , had the potential to be a new type of far-red luminescent powder for indoor plant growth LEDs.

Dual-emitting temperature dependent material based on Bi3+/Eu3+ co-activated Ba2Y2Si4O13 phosphor with multicolor anti-counterfeiting

Bi3+, Eu3+ co-doped Ba2Y2Si4O13 phosphors with multi-color luminescence properties were prepared by high temperature solid state method. The structure, luminescent properties and temperature characteristics were studied by X-ray diffraction, scanning electron microscope, fluorescence spectrum and temperature-dependence of emission spectrum. Ba2Y2Si4O13: Bi3+, Eu3+ phosphors can emit color from cyan to red when the excitation wavelength was changed from 340 nm to 390 nm, which is attributed to that there are two Bi3+ ion emission centers, and their emission intensity will change with the change of excitation wavelength. Moreover, the emission of the phosphor has good temperature sensing characteristics, based on the fluorescence intensity ratio of the two blue emission bands of Bi3+ and the red emission peak of Eu3+, a multimode thermometer with high temperature sensitivity was constructed. At the same time, based on the dynamic luminescence characteristics of the phosphor, the dynamic anti-counterfeiting experiments are designed. Therefore, the results show that the material has a bright prospect in the field of temperature sensing and anti-counterfeiting.

Antithermal Quenching and Multiparametric Temperature Sensing from Mn2+/Tb3+‐Codoped Ca2LaTaO6 Phosphor

Luminescence thermometry plays significant roles in various fields including industrial production, environmental detection, aerospace, and medicine. However, its accuracy improvement remains highly challenging due to the thermal quenching effect of phosphors. Herein, for the first time, a thermal‐activated electron compensation Mn2+‐ and Tb3+‐codoped Ca2LaTaO6 phosphor is developed for multiparametric temperature sensing with tunable emission of Mn2+ and antithermal quenching emission of Tb3+, leading to excellent accuracy at high temperatures. By virtue of the deep electron trap states induced by Mn2+ dopant, the electrons in the deep trap can be thermally activated at high temperatures, which can replenish the attenuated Tb3+ emission caused by thermal quenching, thus bringing out the antithermal quenching phenomenon. On account of the prominent emission properties, the luminescence intensity ratio (LIR) readout and lifetime‐based thermometry are designed, providing a maximum relative sensitivity SR of 3.603% and 1.941% K−1, respectively. Multiparametric temperature sensing and novel data analysis are also employed to further improve the accuracy of the luminescence thermometer. The outstanding relative thermal sensitivity ranging from 8.72% to 16.11% K−1 and temperature uncertainty order of 10−3 are achieved. These results demonstrate that the designed Ca2LaTaO6:Mn2+/Tb3+ phosphor material is a promising thermal‐sensing candidate.

Synthesis and up-conversion luminescence of Ho3+ and Yb3+ co-doped La7P3O18 phosphors

Ho3+ and Yb3+ co-doped La7P3O18 up-conversion phosphors were prepared by a high-temperature solid-state process. XRD results reveal that the samples are mixtures of monoclinic structure La7P3O18 crystals with P21/n space group and minor LaPO4 crystals. UV—Vis DRS results indicate that La7P3O18 crystal is an indirect semiconductor with an optical band gap of 4.10 eV. After 980 nm laser excitation, the Ho3+ and Yb3+ co-doped La7P3O18 phosphors show the characteristic blue (486 nm), green (550 nm), and red (661 nm) luminescence peaks of Ho3+ ions. The peak at 661 nm dominates in the up-conversion luminescence spectra of samples. Meanwhile, with the increase of Ho3+ and Yb3+ doping content, the up-conversion luminescence intensity increases first and then decreases. By increasing the doping contents of Ho3+ and Yb3+ up to 1 at.% and 10 at.%, respectively, concentration quenching may appear by an electric quadrupole– electric quadrupole interaction process. The pumping power dependence of luminescence indicates that the green and red emissions of samples are excited by a two-photon absorption process. The color coordinates of Ho3+ and Yb3+ co-doped La7P3O18 crystals locate in the orange—red region.

Up-conversion luminescence performance of Yb3+, Er3+/Ho3+ co-doped Y2W3O12 phosphors

Up-conversion luminescence performance of Yb3+, Er3+/Ho3+ co-doped Y2W3O12 phosphors

Luminescent ionic lattice occupation and wide tunable emission spectra of La2MgZrO6:Bi3+,Eu3+ double perovskite phosphors for white light LED

La 2 Mg 1– x /2 Zr 1– x /2 O 6 : x Bi 3+ ( x = 0.01–0.035, abbreviated as LMZ:Bi 3+ ) and La 2– y Mg 0.99 Zr 0.99 O 6 :0.02Bi 3+ , y Eu 3+ ( y = 0.1–0.11, abbreviated as LMZ:Bi 3+ ,Eu 3+ ) double-perovskite phosphors were prepared through high-temperature solid-phase method. The emission spectrum of LMZ: x Bi 3+ ( x = 0.01–0.035) phosphors excited at 353 nm is asymmetric in the range between 375 and 650 nm, showing strong green light. There are two luminescent centers of [Mg1/Zr2–O 6 ] and [Mg2/Zr1–O 6 ] for Bi 3+ occupation, which were analyzed through different excitation wavelengths, Gaussian fitting peaks, fluorescence decay curves and Rietveld refinement of powder X-ray diffraction data. Through deep study of the luminescent lattices in the LMZ matrix, the green to blue tunning-emission is observed by different excitation wavelengths. In addition, red emission is obtained by co-doping Bi 3+ /Eu 3+ , and adjustable emission was investigated by changing the content of Eu 3+ in the co-doped phosphor formulation, so it is converted from green emission to red emission. The above results demonstrate how to tune emission color by co-doping rare earth ions in the double perovskite phosphor, which is attractive for future applications. The Gaussian deconvolution of the emission spectrum of LMZ:Bi phosphors was performed to obtain two sub-Gaussian components, and the selective site occupancy of Bi 3+ was analyzed. By co-doping Bi 3+ and Eu 3+ , the luminescence intensity of Eu 3+ can be effectively improved.

Photoluminescence and temperature dependent properties of Bi3+, Sm3+ co-doped Ca2YSbO6 phosphor for dual-emitting optical thermometer

Bi3+, Sm3+ co-doped Ca2YSbO6 phosphors with dual-emitting centers were created using a high-temperature synthetic process. Investigations were conducted into the phase structure, luminous characteristics, and optical temperature dependent properties. Under the condition of 320 nm Ultraviolet light excitation, the Ca2YSbO6: Bi3+ phosphor exhibits the 3P1→1S0 emission of Bi3+, which peaked at 402 nm, and the Ca2YSbO6: Sm3+ phosphor exhibits the 4G5/2→6Hn/2 (n = 5, 7, 9 and 11) red emission of Sm3+, which is visible between 550 and 720 nm. Spectrum overlap between the PL spectrum of Bi3+ and the PLE spectrum of Sm3+ served as evidence for the energy transfer (ET) behavior. Furthermore, the conclusion could be supported by the life decay of Bi3+.In the case of optimal UV excitation of 320 nm, the maximum absolute sensitivity (Sa) and relative sensitivity (Sr) values for Ca2YSbO6: Bi3+, Sm3+ were 2.21 × 10−3 K−1 and 0.973% K−1, respectively, at 503 K. The outcomes demonstrated that the Ca2YSbO6: Bi3+, Sm3+ phosphor could perform well as an optical thermometer.

Designing a dual-wavelength excitation Eu3+/Mn4+ co-doped phosphors for high-sensitivity luminescence thermometry

Luminescence thermometry has been widely concerned by researchers due to its quick response, high spatial resolution, and remote measurement. However, low sensitivity is still an existing problem and affects its development. Herein, the luminescence thermometer with high sensitivity taking advantage of the distinguished thermal response between Eu3+ and Mn4+ is designed. Excitedly, Eu3+ exhibits an anti-thermal quenching behavior under 310 nm excitation and a slight thermal quenching behavior under 393 nm excitation due to the energy transfer of host→Eu3+, while Mn4+ presents a strong thermal quenching behavior. Moreover, the energy transfer of Eu3+→Mn4+ (λex = 310 nm and λex = 393 nm) can also be observed for the Ca2Sb2O7: Eu3+, Mn4+ phosphors during the heating process. On the basis of the diverse thermal quenching behavior of Eu3+ and Mn4+, the thermometric performances are investigated by utilizing the fluorescence intensity ratio (FIR) of Eu3+(5D0→7F2)/Mn4+(2Eg→4A2g) under a dual-wavelength excitation. The maximum relative sensitivities of the designed phosphors are determined to be 4.072% K−1 at 305 K under 310 nm and 3.072% K−1 at 351 K under 393 nm excitation. It's worth noting that the thermometric characteristic can be modified by various excitation wavelengths. Hence, the developed Ca2Sb2O7: Eu3+, Mn4+ phosphors have great potential in the field of luminescence thermometry and provide an effective strategy for designing high-sensitivity dual-wavelength excitation optical thermometers.

X-ray-activated Bi3+/Pr3+ co-doped LiYGeO4 phosphor with UV and NIR dual-emissive persistent luminescence

X-ray-activated luminescence materials have broad application prospects in photodynamic therapy of deep tissue. Among them, X-ray-activated persistent luminescence materials (PLMs) exhibiting multiple emission peaks have drawn extensive attention for their capacity to achieve a combination of bioimaging and therapeutic functions. Here, we developed a novel PLM, LiYGeO4:Bi3+,Pr3+, that simultaneously exhibits UV and NIR dual persistent luminescence (PersL) emissions after irradiation by X-ray. The material can be repeatedly excited by X-ray and emits similar luminescence intensity every time, which shows good PersL stability. In addition, LiYGeO4:Bi3+,Pr3+ exhibits photostimulated PersL properties by stimulation with a red light-emitting diode (LED) or NIR laser after long-term decay. This work provides a new choice of X-ray-excited PLMs with UV and NIR dual emission and the novel phosphor shows promise as a potential candidate for the integration of treatment and diagnosis of deep tumors.

Narrow UVB-Emitted YBO3 Phosphor Activated by Bi3+ and Gd3+ Co-Doping.

Y0.9(GdxBi1-x)0.1BO3 phosphors (x = 0, 0.2, 0.4, 0.6, 0.8, and 1.0, YGB) were obtained via high-temperature solid-state synthesis. Differentiated phases and micro-morphologies were determined by adjusting the synthesis temperature and the activator content of Gd3+ ions, verifying the hexagonal phase with an average size of ~200 nm. Strong photon emissions were revealed under both ultraviolet and visible radiation, and the effectiveness of energy transfer from Bi3+ to Gd3+ ions was confirmed to improve the narrow-band ultraviolet-B (UVB) (6PJ→8S7/2) emission of Gd3+ ions. The optimal emission was obtained from Y0.9Gd0.08Bi0.02BO3 phosphor annealed at 800 °C, for which maximum quantum yields (QYs) can reach 24.75% and 1.33% under 273 nm and 532 nm excitations, respectively. The optimal QY from the Gd3+-Bi3+ co-doped YGB phosphor is 75 times the single Gd3+-doped one, illustrating that these UVB luminescent phosphors based on co-doped YBO3 orthoborates possess bright UVB emissions and good excitability under the excitation of different wavelengths. Efficient photon conversion and intense UVB emissions indicate that the multifunctional Gd3+-Bi3+ co-doped YBO3 orthoborate is a potential candidate for skin treatment.

Upconversion luminescence of La4Ti9O24: Er–Yb phosphor with high green color purity

Upconversion materials with high green color purity are considered to have greater potential in the development and manufacturing of modern optoelectronic devices. However, the generation of high green color purity in Er3+-Yb3+ ions doped upconversion materials is usually a great challenge. Herein, we develop a series of Er3+ singly doped, and Er3+-Yb3+ co-doped La4Ti9O24 phosphors with high green color purity under 980 nm irradiation. The green emission of the phosphor was not changed by increasing Yb3+ concentrations, and the material exhibited excellent color purity. We found that low phonon energy and layered structure are the main causes of high green color purity by analyzing Raman spectrum and crystal structure. Based on CIE chromaticity estimates from 1931 in terms of coordinates, dominant wavelength, and color purity, La4Ti9O24: 3 mol% Er3+ and La4Ti9O24: 3 mol% Er3+-16 mol% Yb3+ presents the color purity of 95.14% and 96.04%, respectively.