Luminescence Properties Of Ce3 Research Articles

Folic Acid Passivated Efficient Cerium Doped Perovskite Nanocrystals for High‐Performance Light‐Emitting Diodes

AbstractThe 5d→4f transition of Ce3+ is allowed by the electric dipole and the parity selection rule and the position/intensity of the 5d excited state is strongly dependent on the materials’ composition and atomic structure. Herein, the composition‐dependent luminescence properties of Ce3+ in CsPbCl3‐xBrx (0 ≤ x ≤ 3) perovskite nanocrystals (PeNCs) are systematically revealed. It's observed that the 5d‐4f broadband emission of Ce3+ is greatly improved by optimizing the Cl:Br ratio due to the efficient energy transfer from excitons to Ce3+. Folic acid, a vitamin which is an extremely important cofactor, is introduced to regulate the film formation by interacting with uncoordinated ions. The modified CsPbCl1.5Br1.5 PeNCs with photoluminescence quantum yield of 91% represent a novel and extremely efficient white nanophosphor. Then, white light‐emitting diodes (WLEDs) are constructed by combining Ce3+‐doped PeNCs with 400‐nm ultraviolet chips with a luminous efficiency of 120.3 lm W−1, which is the most efficient perovskite single‐component WLED. Moreover, the blue‐violet LEDs are fabricated with external quantum efficiency of 0.84%, representing extremely high level of 400–435 nm perovskite LEDs. This work demonstrates the strategy in realizing high‐efficiency wavelength‐tunable PeNCs, motivating the further exploration of Ce3+‐doped perovskites in optoelectronic devices.

Preparation, structure and luminescence properties of Ce3+: Y3(Al,Ga)5O12 translucent glass ceramics for AC-LEDs

Translucent glass ceramics containing Ce3+:Y3(Al,Ga)5O12 microcrystals were prepared by spontaneous crystallization in the SiO2–B2O3–Al2O3–Ga2O3–Y2O3–PbO–CeF3 glass system. The sample exhibits around 45 % transmittance in the range of 500–800 nm. X-ray diffraction patterns confirm the garnet phases. Scanning electron microscope and laser scanning confocal microscopy images suggest that about 5 μm grains are dispersed uniformly in the glass matrix. With increasing Ga/Al ratio in the components, both excitation and emission peaks blue shift. The emission intensity reaches to the maximum at Ga/Al ratio of 8/22, and the optimized Ce3+ content is 0.4 mol%. The sample exhibits yellowish-green persistent luminescence with lifetime of 47.3 ms. The glass ceramic-based device exhibits near standard white light emission with luminous efficiency of 64.7 lm/W, correlated color temperature of 6979 K, color rendering index of 65.4 and flicker index of 76.9 %. It indicates that the Ce3+:Y3(Al,Ga)5O12 glass ceramics are promising in the alternating current directly driven white light-emitting diodes (AC-LEDs).

Physical and luminescence properties of Ce3+ activated strontium phosphate glasses

Strontium phosphate (SrO–P2O5–Al2O3–Gd2O3) glasses with 0.05, 0.1, 0.5, and 1 mol % CeO2 were prepared by the conventional melt quenching technique. These glasses' luminescence, scintillation, and physical properties were measured and discussed in detail. The density, refractive index, and oxygen packing density of the studied glasses were increased with an increase in CeO2 concentration. At lower concentrations of CeO2, the characteristic 310 nm emission from Gd3+ and broadband emission from Ce3+ ions were obtained under X-ray excitations. The intensity of both Gd3+ and Ce3+ emission bands under 270 nm Gd3+ excitations reduced with further increase in CeO2, showing the delayed energy transfer from Gd3+ to Ce3+ ions. The integrated X-ray-induced luminescence intensity of 0.5% CeO2 glass was found to be 21% that of reference BGO crystal. For the lower concentration of CeO2, a slow decay time along with the fast Ce3+ decay was observed and disappears for higher CeO2 concentrations. The fast luminescence decay in the range of 22 ns–30 ns was observed for all the PSAG:Ce glasses, which was attributed to the lifetime of the 4f-5d transition of the Ce3+ ions. The faster decay time and reasonable scintillation light suggest the application of these glasses for radiation detector applications.

Luminescence properties of Ce and Be-doped CaAl12O19 for dosimetric and light-emitting applications

In this study, we reported the sol-gel production of cerium (Ce) and beryllium (Be)-doped calcium aluminate (CaAl12O19) and its luminescence properties for optically stimulated luminescence (OSL) dosimetry and light-emitting applications. Structural, morphological and elemental characteristics of the samples were examined by x-ray diffraction (XRD), Scanning electron microscope (SEM)/energy dispersive spectrum (EDS), x-ray fluorescence (XRF) and Inductively Coupled Plasma-Mass Spectroscopy (ICP-MS) techniques. The maximum OSL intensity was achieved with 0.5 and 2% mol concentrations of Ce and Be dopants, respectively. We investigated the OSL and thermoluminescence (TL) properties of Ce and Be-doped CaAl12O19 by measuring energy storage for 24 h, dose-response in the range of 0.1 and 20 Gy, and reusability of the samples for 15 cycles. Photometric properties of the phosphors were investigated by evaluation of CIE chromaticity coordinate (x, y), CCT, and colour purity using its corresponding photoluminescence (PL) emission spectra. We also applied computerized glow curve deconvolution (CGCD), various heating rate methods, and the Tm-Tstop procedure to determine the trap localizations associated with the TL glow curve. The results of this study point out that CaAl12O19 crystals have the potential to be used as OSL dosimetry when appropriate dopants are used. This study may offer new possibilities in radiation dose detection and monitoring.

Effect of ZnO on structure and luminescence properties of Ce3+-Yb3+ co-doped Na2O–CaO–SiO2–Al2O3 glasses for solar panel applications

The Ce3+-Yb3+ co-doped Na2O–CaO–SiO2–Al2O3–ZnO glasses were prepared by the melt-quenching method. The effects of ZnO replacing CaO on the structure and luminescent properties of glass were studied. The thermodynamic temperature and thermal stability of the glasses were determined by DSC. The change in the glass network structure was analyzed by FT-IR spectra. The excitation spectrum, emission spectrum and fluorescence lifetime of Ce3+ in glass were determined by fluorescence spectrometer. The down-conversion luminescence spectra of Ce3+-Yb3+ ions excited at 355 nm were measured. According to the emission spectra of Ce3+ ions under different excitation wavelengths, the multiple luminescence centers of Ce3+ ions are determined, and the chromaticity coordinates of CIE are calculated. Finally, the energy transfer between Ce3+ and Yb3+ was analyzed. The Ce3+-Yb3+ co-doped glass can convert ultraviolet and visible light to the response band of c-Si solar cells, so it is an ideal candidate for solar panel glass.

Na1.5Y2.5F9: Ce3+, Tb3+, Eu3+ glass-ceramics for white light

A simply encapsulated, long-range excitation method for white light generation was proposed. Na1.5Y2.5F9: Ce3+, Tb3+, Eu3+ (NYFCTE) glass-ceramics (GCs) were synthesized by the melt-quenching method. The effect of crystallization temperature on the formation of crystallites was analyzed by X-ray diffraction (XRD). The morphology and size of nanocrystals were investigated by transmission electron microscope (TEM). The unit cell diagram of Na1.5Y2.5F9 nanocrystals was drawn. In addition, the luminescence properties of Ce3+, Tb3+, Eu3+ ions-doped Na1.5Y2.5F9 GCs were tested and analyzed. The sample NYFCTE2 emits bright white light when excited by a 320 nm light source at a distance from the light source. The NYFCTE2 sample obtained white light with Commission Internationale de L'Eclairage (CIE) coordinate of (0.3110, 0.3472), Correlated Color Temperature (CCT) of 6467.72 K, and reliable thermal stability. The above results indicate that the proposed white light generation method and NYFCTE GCs have immense application prospects for illumination.

Effect of extra added Mg2+ and Si4+ on the microstructure and luminescence properties of Ce:YAG ceramic phosphors for high power LED/LD lighting

The study deals with the use of different amounts of MgO or tetraethyl orthosilicate (C8H20O4Si, TEOS), from 0.04 wt %, 0.06 wt %, 0.08 wt %, 0.4 wt %, 0.6 wt % to 0.8 wt %, respectively, as additional sintering aids during the vacuum sintering of transparent Ce3+ doped Y3Al5O12 (Ce:YAG) ceramics to investigate their effect on microstructure and luminescence properties. A comparative study was carried out by using X - ray diffraction, scanning electron microscopy/energy dispersive X - ray spectroscopy, optical and photo-luminesce spectra, as well as electroluminescent spectra. The dominant garnet phase was obtained even when adding 0.8 wt % of MgO or TEOS, while adding MgO led to finer average grain size (∼ 5 - 10 μm) and more homogenous distribution compared to TEOS (∼ 20 - 25 μm) in Ce:YAG ceramics. Adding a large amount of MgO was found to result in the segregation of MgO in Ce:YAG ceramics, while an excess of TEOS led to the segregation of Al2O3. A strong absorption peak at 308 nm was observed in Ce:YAG ceramics with MgO sintering aids, which was ascribed to the existence of Ce4+ induced by a charge compensation effect of Mg2+. The optimum transmittance reached 80% @ 800 nm in Ce:YAG ceramics when adding 0.6 wt % TEOS, which also exhibited a maximum luminous efficacy of 106 lm/W. Si4+ was experimentally proved to have a better optimization effect on luminous efficacy compared to Mg2+.

Preparation, structure and luminescence properties of Ce3+ activated translucent glass ceramics containing garnet microcrystals

Glass ceramics containing Ce3+ doped garnet microcrystals were prepared from the spontaneous crystallization of SiO2-Al2O3-Y2O3-MgO-BaO-CeF3 glass melt. The formation of Ce3+:(Y,Mg)3(Al,Si)5O12 grains in the glass matrix were investigated by X-ray diffraction, scanning electron microscope and photoluminescence spectra. The transmittance of samples improves with higher melting temperature or increasing BaO/MgO ratio, while the Ce3+: 5d → 4f emission intensity weakens monotonously. Besides, the transmittance declines sharply after being heat treated above 950°C, which is originated from the schistose BaAl2Si2O8 microcrystals in the glass matrix. The optimized sample with composition of 40SiO2-16Al2O3-8Y2O3-24BaO-12MgO-0.3CeF3 was chosen to construct a white LED device, which yields bright white light with luminous efficiency of 23.6 lm/W, correlated color temperature of 5260 K and Ra of 85.5. It indicates that the investigated glass ceramics can be a promising color converter for white LEDs.

Simple synthetic route to Ca18.75Li10.5[Al39N55]:Ce3+ yellow-green phosphors for white LEDs

Nitride phosphors usually have great influence on the performance of white LEDs. However, most nitrides require synthesis under high temperature and high pressure, especially Ca18.75Li10.5[Al39N55] (CLAN), which demands preparation even under a pressure of 51.7 MPa. Herein, we applied a simple synthetic route to obtain CLAN at a low pressure of 0.85 MPa and temperature of 1250 °C. In addition, the luminescence properties of Ce3+ doped CLAN were studied and the CLAN:Ce3+ shows three excitation bands peaked at 267, 387, and 478 nm. Two emission peaks are located at 513 nm and 567 nm, corresponding to the d-f electronic transition of Ce3+, respectively. The emission intensity at 150 °C retains about 83.3% of the initial value at room temperature, indicating a good thermal stability. A prototype white LED encapsulated with a 450 nm chip and the CLAN:Ce3+ phosphor exhibits bright white emission, indicating potential applications.

Effect of Gd2o3 and Gdf3 on Physical and Luminescence Properties of Ce3+ Ions Doped Phosphate Glasses: A Comparative Study

Effect of Gd2o3 and Gdf3 on Physical and Luminescence Properties of Ce3+ Ions Doped Phosphate Glasses: A Comparative Study

Site occupancy and luminescence of Ce3+-doped NaK2Li[Li3SiO4]4: A first-principles study

The observed photoluminescent properties of Ce3+-doped NaK2Li[Li3SiO4]4 suggest the importance and potential of this phosphor in practical applications. It is noted that only half of the Na+ and Li + sites in the Na/Li channel are found to be occupied in the host and two sets of different luminescent Ce3+ centers are observed. In this work, first-principles calculations are performed to resolve the site occupancy of Ce3+ by taking experimental synthesis conditions into consideration. The formation energy results show that Ce3+ prefers to replace the Na atom in the Na/Li channel than K atom in the K channel, whilst the cation vacancies VLi, VNa and VK are formed as charge compensation. Besides, a large amount of Ce4+ would be present. Based on the obtained excitation and emission energies, the Stokes shifts, and the 5d crystal-field splitting, the luminescent center with a larger red-shift of the emission wavelength is assigned as Ce at the Na site, and the other center is assigned as Ce at the K site. The energy level structures of Ce occupying a certain site (Na site or K site) with different local environments differ slightly, thus the broadening of the spectra can be interpreted. Furthermore, we provide an explanation on the excellent thermal stability of this phosphor based on the large energy barrier for the 5d-4f crossover point and the large 5d thermal ionization energy. To sum up, the insights gained in this work deepen our understanding on the luminescent properties of Ce3+-doped NaK2Li[Li3SiO4]4 in which some of the host cation sites are partially occupied.

252Cf -induced luminescence of cerium-doped lithium silicate glasses

In addition to the total attenuation of ionizing radiation, photoluminescence has been conventionally recognized to affect radiation-induced luminescence. In this study, we examined the optical and luminescence properties of Ce3+ in lithium silicate-based glasses with different optical basicities. The existence of Ce4+ was confirmed based on the optical absorption, Ce L3-edge X-ray absorption near edge structure (XANES), and optical coefficients of the calculated Ce4+ using the optical absorption and XANES data of Ce4+ species from a previous report. Compared to other multicomponent glasses, there was a slight deviation in the decay constant and quantum yield (QY) of the stoichiometric Li2O–2SiO2 glass. In addition, the light yields calculated from the pulse height spectra with 252Cf irradiation depend on the QY of the glasses. Considering the energy conversion process, the dependence of the light yield agreed with that of the conventional energy conversion process of neutron-induced luminescence.

Efficient spectral regulation in Ce:Lu3(Al,Cr)5O12 and Ce:Lu3(Al,Cr)5O12/Ce:Y3Al5O12 transparent ceramics with high color rendering index for high-power white LEDs/LDs

Realizing a high color rendering index (CRI) in Ce:LuAG transparent ceramics (TCs) with desired thermal stability is essential to their applications in white LEDs/LDs as color converters. In this study, based on the scheme of configuring the red component by Cr3+ doping, an efficient spectral regulation was realized in Ce,Cr:LuAG TCs. A unilateral shift phenomenon could be observed in both photoluminescence (PL) and photoluminescence excitation (PLE) spectra of TCs. By constructing TC-based white LED/LD devices in a remote excitation mode, luminescence properties of Ce,Cr:LuAG TCs were systematically investigated. The CRI values of Ce:LuAG TC based white LEDs could be increased by a magnitude of 46.2%. Particularly, by combining the as fabricated Ce,Cr:LuAG TCs with a 0.5 at% Ce:YAG TC, surprising CRI values of 88 and 85.5 were obtained in TC based white LEDs and LDs, respectively. Therefore, Ce,Cr:LuAG TC is a highly promising color convertor for high-power white LEDs/LDs applied in general lighting and displaying.

Luminescent properties of Ce3+-activated lithium borosilicate glasses tuned by various ratios of lithium to boron

Motivated by the urgent practical requirement of neutron detection, Ce3+-activated lithium borosilicate glasses consisting of 80 mol% lithium and boron mixtures with high neutron capture cross-section were synthesized by melt quenching method in air. The structures of lithium borosilicate glasses were revealed by both FTIR and Raman spectra. The effects of Li/B ratios on the optical properties, such as optical transmittance, photoluminescence, decay lifetime and radioluminescence (RL) were investigated in detail. It is found that the integrated emission intensity of Ce3+ ions can be enhanced by a factor of 13.5 and 1.2 under UV light and X-ray excitation, respectively. The developed Ce3+-activated lithium borosilicate glass is featured with the emission band centered at 350 nm and the lifetime within 25–30 ns, which shows promising application for thermal neutron detection.

Luminescence properties of Ce3+- doped borate scintillating glass for new radiation detection material

A series of glasses composed (Ce3+ and Gd3+) co-doped lithium aluminum borate glasses with composition 25Li2O–5Al2O3-XGd2O3-(69.5-X)B2O3-0.5CeF3 glasses were successfully synthesized by using a conventional melt-quenching technique and characterized through physical, structural and luminescence properties. The optimal doping concentration of CeF3 contents is 0.5 mol% and varying Gd2O3 concentration for studying the combined effect of dual doped glass. Further, the phenomenon of energy transfer from the host glass in luminescence center was observed by x-rays induced luminescence spectra, as well as from Gd3+to Ce3+ ions are confirmed by photoluminescence emission spectra. The strongest emission intensity of Ce3+emission is obtained when the scintillating glass contains 5.0 mol% of Gd2O3 concentration. From the nano-second decay time of glass exhibit a high potential for using as scintillating materials.

Radiation-induced luminescence of Ce-doped SrO–B2O3 glasses

Abstract The performance of phosphors generally depends on the local coordination of activators. The luminescence properties are also affected by the excitation light source and radiation-induced luminescence, like X-ray-induced scintillation, is quite different from conventional photoluminescence (PL) excited by UV light. Here, we have examined the optical and luminescence properties of Ce3+ in strontium borate glasses. The pulse height spectra by 241Am irradiation indicate that the X-ray induced luminescence intensity detected consists of prompt scintillation and storage luminescence. Persistent luminescence at room temperature was clearly observed in B2O3-rich glass after X-ray and UV irradiation. In the present borate glass system, B2O3-rich glass exhibiting a deep optical absorption edge is favorable for high luminescence intensity by UV irradiation and storage luminescence, while SrO-rich glass is suitable for high detection ability of α-rays.

Recent progress of effect of crystal structure on luminescence properties of Ce3+-Eu2+ Co-doped phosphors.

Currently, the mechanism of Ce3+–Eu2+ ET is frequently used to obtain color adjustable or white phosphors. Correspondingly, the ET efficiency from Ce3+ to Eu2+ becomes an important indication of the luminescent properties of phosphors. However, the ET efficiency calculated using the formula does not always match the emission spectra; the transmission efficiency of Ce3+ is high, but the emission efficiency of Eu2+ is low, depending on our investigation results. In addition to this problem, here we mainly review, on the basis of substantial examples, how to boost the actual ET efficiency of Ce3+-to-Eu2+ and thus to improve the luminescent properties of phosphors through the rational design of layered crystal structure and the way of selective occupation of activator ions. Moreover, the possible physical mechanisms are proposed.

Luminescence tuning of Ce3+, Pr3+ activated (Y,Gd)AGG system by band gap engineering and energy transfer

Tuning of phosphor luminescence properties, including the emission energy/intensity and thermal stability, is an important way to develop superior luminescent materials for diverse applications. In this work, we discuss the effect of band gap engineering and energy transfer on the luminescence properties of Ce3+ or Pr3+ doped (Y,Gd)AGG systems, and analyze the underlying reasons for their different phenomena. By using VUV-UV excitation spectra and constructing VRBE schemes, the changes of host band structure, 5d excited level energies and emission thermal stability of Ce3+ and Pr3+ with the incorporation of Gd3+ ions were studied. In addition, the energy transfer dynamics was also investigated in terms of the luminescence decay curves. This work demonstrates a way to tune phosphor luminescence properties by combining band gap engineering and energy transfer tailoring and provides an inspiring discussion on the different results of Gd3+ doping on the Ce3+ and Pr3+ emissions.

Effect of grain size on the luminescent properties of Ce3+ doped Y3Al5O12 ceramic phosphor plates

Ceramic phosphor plates of Ce3+ doped Y3Al5O12:Ce (or YAG:Ce) are considered better wavelength converters for high power light emitting diode (LED) and laser diode (LD) lighting applications due to their significantly better thermal conductivity and heat resistance as compared to phosphor powder/epoxy films. Understanding the relationship between the microstructures of YAG:Ce ceramic phosphor plates and their luminescent properties is of importance to optimize their luminescent properties. In this work, we have found that the grain size of Ce3+ doped YAG ceramic phosphor plates has a significant effect on their luminescent properties. Our results show that ceramic phosphor plates with larger grains size can not only convert blue light to yellow light more efficiently, but also have better resistance to thermal quenching. When excited by a blue light source (peak wavelength of 455 nm, optical power of 24.75 W) generated by an LED COB, the ceramic phosphor plate with average grain size of 36 μm is found to have blue-to-yellow light conversion efficiency 46% higher than that of the sample with average grain size of 6 μm (309 lm W−1 vs 213 lm W−1). As they are heated from 300 K to 473 K, their emission intensities decrease by 15%, 19% and 21% for the samples with average grain sizes of 36 μm, 9 μm and 6 μm, respectively.

Structural and luminescence properties of Ce3+-doped hydroxyapatite nanocrystalline powders

Ce3+-doped apatites have been synthesized by precipitation method in the range of the Ce/Ca atomic ratio in solutions from 0.05 to 5%. Obtained precipitates were studied with X-ray powder diffraction, infrared spectroscopy, scanning electron microscopy, EDX and luminescence spectroscopy. Cerium content in the synthesized apatites reaches 0.33 apfu (Ce/Ca = 3.9%). Relations between Ce content in the solution and precipitate have been established. It was revealed that during synthesis Ce-monazite starts to precipitate as a secondary phase at 1% Ce/Ca ratio in starting solution. Doping concentration effect on the luminescence intensity and lifetime of HAp:Ce3+ nanophosphors was studied in detail. Optimum doping concentration of Ce3+ ions in hydroxyapatite host was determined to be 0.3% of the Ce/Ca atomic ratio, which corresponds to 0.5% of the Ce/Ca ratio in the starting solution. The luminescence quenching occurs through energy transfer among the nearest neighbor Ce3+ ions.