A series of new long afterglow phosphors Ca2SnO4:x Tm3+ were synthesized by using traditional solid‐state reactions. XRD measurements and Rietveld refinement revealed that the incorporation of the Tm3+ dopants generated no second phase other than the original one of Ca2SnO4, which indicated that the dopants completely merged into the host. The corresponding optical properties were further systematically studied by photoluminescence, phosphorescence, and thermoluminescence (TL) spectroscopy. The results show that the Tm3+‐related defects account for the bright bluish green afterglow emission from the characteristic f–f transitions of Tm3+ ions. The bluish green long‐lasting phosphorescence could be observed for 5 h by the naked eye in a dark environment after the end of UV irradiation. Two TL peaks at 325 and 349 K from the TL curves were adopted to calculate the depth of the traps, which were 0.45 and 0.78 eV, respectively. The mechanism of the long afterglow emission was also explored. 相似文献
Learning from natural mineral structures is an efficient way to develop potential host lattices for applications in phosphor converted (pc)LEDs. A narrow‐band blue‐emitting silicate phosphor, RbNa3(Li3SiO4)4:Eu2+ (RNLSO:Eu2+), was derived from the UCr4C4‐type mineral model. The broad excitation spectrum (320–440 nm) indicates this phosphor can be well matched with the near ultraviolet (n‐UV) LED chip. Owing to the UCr4C4‐type highly condensed and rigid framework, RNLSO:Eu2+ exhibits an extremely small Stokes shift and an unprecedented ultra‐narrow (full‐width at half‐maximum, FWHM=22.4 nm) blue emission band (λem=471 nm) as well as excellent thermal stability (96 %@150 °C of the initial integrated intensity at 25 °C). The color gamut of the as‐fabricated (pc)LEDs is 75 % NTSC for the application in liquid crystal displays from the prototype design of an n‐UV LED chip and the narrow‐band RNLSO:Eu2+ (blue), β‐SiAlON:Eu2+ (green), and K2SiF6:Mn4+ (red) components as RGB emitters. 相似文献
A SrLiAl3N4:Eu2+ (SLA) red phosphor prepared through a high‐pressure solid‐state reaction was coated with an organosilica layer with a thickness of 400–600 nm to improve its water resistance. The observed 4f65d→4f7 transition bands are thought to result from the existence of Eu2+ at two different Sr2+ sites. Luminescence spectra at 10 K revealed two zero‐phonon lines at 15377 (for Eu(Sr1)) and 15780 cm?1 (for Eu(Sr2)). The phosphor exhibited stable red emission under high pressure up to 312 kbar. The configurational coordinate diagram gave a theoretical explanation for the Eu2+/3+ result. The coated samples showed excellent moisture resistance while retaining an external quantum efficiency (EQE) of 70 % of their initial EQE after aging for 5 days under harsh conditions. White‐light‐emitting diodes of the SLA red phosphor and a commercial Y3Al5O12:Ce3+ yellow phosphor on a blue InGaN chip showed high color rendition (CRI=89, R9=69) and a low correlated color temperature of 2406 K. 相似文献
Energy efficiency is in! New inorganic luminescent materials can help to increase energy efficiency when used in plasma display panels and white‐light‐emitting diodes (see color diagram; mixing the three emissions A–C produces any given point within the triangle). In mercury‐free fluorescent lamps these phosphors might contribute to environmental protection, and they provide better scintillation materials for medical diagnostics.
A series of novel KBaSc2(PO4)3:Ce3+/Eu2+/Tb3+phosphors are prepared using a solid‐state reaction. X‐ray diffraction analysis and Rietveld structure refinement are used to check the phase purity and crystal structure of the prepared samples. Ce3+‐ and Eu2+‐doped phosphors both have broad excitation and emission bands, owing to the spin‐ and orbital‐allowed electron transition between the 4f and 5d energy levels. By co‐doping the KBaSc2(PO4)3:Eu2+ and KBaSc2(PO4)3:Ce3+ phosphors with Tb3+ ions, tunable colors from blue to green can be obtained. The critical distance between the Eu2+ and Tb3+ ions is calculated by a concentration quenching method and the energy‐transfer mechanism for Eu2+→Tb3+ is studied by utilizing the Inokuti–Hirayama model. In addition, the quantum efficiencies of the prepared samples are measured. The results indicate that KBaSc2(PO4)3:Eu2+,Tb3+ and KBaSc2(PO4)3:Ce3+,Tb3+ phosphors might have potential applications in UV‐excited white‐light‐emitting diodes. 相似文献
The optical properties of a Ho3+/Yb3+ co‐doped CaSc2O4 oxide material are investigated in detail. The spectral properties are described as a function of doping concentrations. The efficient Yb3+→Ho3+ energy transfer is observed. The transfer efficiency approaches 50 % before concentration quenching. The concentration‐optimized sample exhibits a strong green emission accompanied with a weak red emission, showing perfect green monochromaticity. The results of the spectral distribution, power dependence, and lifetime measurements are presented. The green, red, and near‐infrared (NIR) emissions around 545, 660, and 759 nm are assigned to the 5F4+5S2→5I8, 5F5→5I8, and 5F4+5S2→5I7 transitions of Ho3+, respectively. The detailed study reveals the upconversion luminescence mechanism involved in a novel Ho3+/Yb3+ co‐doped CaSc2O4 oxide material. 相似文献
A hitherto unknown synthetic access to alkali lithosilicates, a substance class first described by Hoppe in the 1980s, is reported. With the synthesis and characterization of NaK7[Li3SiO4]8, a new representative has been discovered, expanding the family of known alkali lithosilicates. Astonishingly, NaK7[Li3SiO4]8 and the already established alkali lithosilicates Na[Li3SiO4] as well as K[Li3SiO4] display unforeseen luminescence properties, when doped with Eu2+. Na[Li3SiO4]:Eu2+ exhibits an ultra‐narrow blue, K[Li3SiO4]:Eu2+ a broadband, and NaK7[Li3SiO4]8:Eu2+ a yellow‐green double emission upon excitation with near‐UV to blue light. Consequently, all of the investigated substances of this class of compounds are highly interesting phosphors for application in phosphor converted LEDs. 相似文献
Aurivillius phases have been routinely known as excellent ferroelectrics and have rarely been deemed as materials that luminesce in the near-infrared (NIR) region. Herein, it is shown that the Aurivillius phases can demonstrate broadband NIR luminescence that covers telecommunication and biological optical windows. Experimental characterization of the model system Bi2.14Sr0.75Ta2O9−x, combined with theoretical calculations, help to establish that the NIR luminescence originates from defective [Bi2O2]2+ layers. Importantly, the generality of this finding is validated based on observations of a rich bank of NIR luminescence characteristics in other Aurivillius phases. This work highlights that incorporating defects into infinitely repeating [Bi2O2]2+ layers can be used as a powerful tool to space-selectively impart unusual luminescence emitters to Aurivillius-phase ferroelectrics, which not only offers an optical probe for the examination of defect states in ferroelectrics, but also provides possibilities for coupling of the ferroelectric property with NIR luminescence. 相似文献
A series of Ca9Ga(PO4)7:Ce3+/Tb3+/Dy3+/Mn2+ phosphors with tunable color, in which Ce3+ acts as the sensitizer, was synthesized. Energy transfer (ET) from Ce3+ to Tb3+/Dy3+/Mn2+ was investigated in detail. Tb3+/Dy3+/Mn2+ single-doped Ca9Ga(PO4)7 can exhibit green, yellow, and red emission, respectively. Incorporating Ce3+ into a Tb3+/Dy3+/Mn2+ single-doped Ca9Ga(PO4)7 phosphor can remarkably promote the luminous efficiency of the Tb3+/Dy3+/Mn2+ ions. This enhancement originates from an efficient ET from Ce3+ to Tb3+/Dy3+/Mn2+. The ET was validated by luminescence spectra, decay dynamics, and schematic energy levels. Moreover, the intensity ratio of red emission of Mn2+ to violet emission of Ce3+ was analyzed based on energy-transfer and lifetime measurements. In Ce3+-Tb3+, Ce3+-Dy3+, and Ce3+-Mn2+ doped Ca9Ga(PO4)7, the emitting color changed from violet to green, yellow, and red, respectively, which indicates the potential use of this new tunable phosphor in UV light-emitting diodes. 相似文献
A series of the solid‐solution phosphors Lu3?x?yMnxAl5?xSixO12:yCe3+ is synthesized by solid‐state reaction. The obtained phosphors possess the garnet structure and exhibit similar excitation properties as the phosphor Lu3Al5O12:Ce3+, but with an effectively improved red component in the emission spectrum. This can be attributed to the energy transfer from Ce3+ to Mn2+. Our investigation reveals that electric dipole–quadrupole interactions dominate the energy‐transfer mechanism and that the critical distance determined by the spectral overlap method is about 9.21 Å. The color‐tunable emissions of the Lu3?x?yMnxAl5?xSixO12:yCe3+ phosphor as a function of Mn3Al2Si3O12 content are realized by continuously shifting the chromaticity coordinates from (0.354, 0.570) to (0.462, 0.494). They indicate that the obtained material may have potential application as a blue radiation‐converting phosphor for white LEDs with high‐quality white light. 相似文献
A comprehensive study unveiling the impact of heterovalent doping with Bi3+ on the structural, semiconductive, and photoluminescent properties of a single crystal of lead halide perovskites (CH3NH3PbBr3) is presented. As indicated by single-crystal XRD, a perfect cubic structure in Bi3+-doped CH3NH3PbBr3 crystals is maintained in association with a slight lattice contraction. Time-resolved and power-dependent photoluminescence (PL) spectroscopy illustrates a progressively quenched PL of visible emission, alongside the appearance of a new PL signal in the near-infrared (NIR) regime, which is likely to be due to energy transfer to the Bi sites. These optical characteristics indicate the role of Bi3+ dopants as nonradiative recombination centers, which explains the observed transition from bimolecular recombination in pristine CH3NH3PbBr3 to a dominant trap-assisted monomolecular recombination with Bi3+ doping. Electrically, it is found that the mobility in pristine perovskite crystals can be boosted with a low Bi3+ concentration, which may be related to a trap-filling mechanism. Aided by temperature (T)-dependent measurements, two temperature regimes are observed in association with different activation energies (Ea) for electrical conductivity. The reduction of Ea at lower T may be ascribed to suppression of ionic conduction induced by doping. The modified electrical properties and NIR emission with the control of Bi3+ concentration shed light on the opportunity to apply heterovalent doping of perovskite single crystals for NIR optoelectronic applications. 相似文献
We report a new dicalcium silicate phosphor, Ca2?xEuxSiO4, which emits red light in response to blue‐light excitation. When excited at 450 nm, deep‐red emission at 650 nm was clearly observed in Ca1.2Eu0.8SiO4, the external and internal quantum efficiencies of which were 44 % and 50 %, respectively. The red emission from Ca2?xEuxSiO4 was strongly related to the peculiar coordination environments of Eu2+ in two types of Ca sites. The red‐emitting Ca2SiO4:Eu2+ phosphors are promising materials for next‐generation, white‐light‐emitting diode applications. 相似文献
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