Abstract:The design of luminescent materials with widely and continuously tunable excitation and emission is still a challenge in the field of advanced optical applications. In this paper, we reported a Eu(2+)-doped SiO2-Li2O-SrO-Al2O3-K2O-P2O5 (abbreviated as SLSAKP:Eu(2+)) silicate luminescent glass. Interestingly, it can give an intense tunable emission from cyan (474 nm) to yellowish-green (538 nm) simply by changing excitation wavelength and adjusting the concentration of Eu(2+) ions. The absorption spectra, photo… Show more
“…Thus, the emission bands are extended. In addition, glass phase has the merit of short-range order and long-range disorder, which possess abundant and continuously distinguishable sites available for luminescent activators 43,44 . These abundant sites may also broaden the emission bands.…”
Section: Resultsmentioning
confidence: 99%
“…The decay times sharply reduce with increase in x value, which indicates the increasing possibility of non-radiative transition caused by energy transfer among the Eu 2+ . It has been reported that the energy of an excited Eu 2+ ion is likely to be consumed by another neighboring Eu 2+ or the traps caused by the defects if the distances between these are close enough via a non-radiative way, resulting in a lifetime reduction 43,45 . With the crystallite enlargement, more and more activator ions are located in the interior of the crystals, rather than at the near surface where energy can rapidly transfer to surface defects and then be consumed by high vibrational energies 34 .Figure 11Room temperature decay curves of Ca 2.97 Si 3− x O 3+ x N 4−2 x : 0.03Eu 2+ ( x = 0, 0.5, 0.8, 1, 1.5) phosphors.
…”
Discovery of novel phosphors is one of the main issues for improving the color rendering index (CRI) and correlated color temperature (CCT) of white light-emitting diodes (w-LEDs). This study mainly presents a systematic research on the synthesis, crystal structure variation and photoluminescence tuning of novel (oxy)nitride solid solution Ca3Si3−xO3+xN4−2x: Eu2+ phosphors. XRD refinements show that lattice distortion occurs when x value diverges the optimum one (x = 1). The lattice distortion causes a widening of emission spectrum and an increase of Stokes shift (ΔSS), which leads to a bigger thermal quenching. With decrease of x value, the emission spectrum shows an obvious red-shift from 505.2 to 540.8 nm, which is attributed to the crystal field splitting. The enhanced crystal field splitting also broadens the excitation spectrum, making it possible to serve as the phosphor for near ultraviolet (n-UV) LEDs. A 3-phosphor-conversion w-LED lamp was fabricated with the as-prepared phosphor, which exhibits high CRI (Ra = 85.29) and suitable CCT (4903.35 K). All these results indicate that the Ca3Si3−xO3+xN4−2x: Eu2+ phosphor can serve as the green phosphor for n-UV w-LEDs, with a tunable spectrum by controlling the crystal structure and morphology.
“…Thus, the emission bands are extended. In addition, glass phase has the merit of short-range order and long-range disorder, which possess abundant and continuously distinguishable sites available for luminescent activators 43,44 . These abundant sites may also broaden the emission bands.…”
Section: Resultsmentioning
confidence: 99%
“…The decay times sharply reduce with increase in x value, which indicates the increasing possibility of non-radiative transition caused by energy transfer among the Eu 2+ . It has been reported that the energy of an excited Eu 2+ ion is likely to be consumed by another neighboring Eu 2+ or the traps caused by the defects if the distances between these are close enough via a non-radiative way, resulting in a lifetime reduction 43,45 . With the crystallite enlargement, more and more activator ions are located in the interior of the crystals, rather than at the near surface where energy can rapidly transfer to surface defects and then be consumed by high vibrational energies 34 .Figure 11Room temperature decay curves of Ca 2.97 Si 3− x O 3+ x N 4−2 x : 0.03Eu 2+ ( x = 0, 0.5, 0.8, 1, 1.5) phosphors.
…”
Discovery of novel phosphors is one of the main issues for improving the color rendering index (CRI) and correlated color temperature (CCT) of white light-emitting diodes (w-LEDs). This study mainly presents a systematic research on the synthesis, crystal structure variation and photoluminescence tuning of novel (oxy)nitride solid solution Ca3Si3−xO3+xN4−2x: Eu2+ phosphors. XRD refinements show that lattice distortion occurs when x value diverges the optimum one (x = 1). The lattice distortion causes a widening of emission spectrum and an increase of Stokes shift (ΔSS), which leads to a bigger thermal quenching. With decrease of x value, the emission spectrum shows an obvious red-shift from 505.2 to 540.8 nm, which is attributed to the crystal field splitting. The enhanced crystal field splitting also broadens the excitation spectrum, making it possible to serve as the phosphor for near ultraviolet (n-UV) LEDs. A 3-phosphor-conversion w-LED lamp was fabricated with the as-prepared phosphor, which exhibits high CRI (Ra = 85.29) and suitable CCT (4903.35 K). All these results indicate that the Ca3Si3−xO3+xN4−2x: Eu2+ phosphor can serve as the green phosphor for n-UV w-LEDs, with a tunable spectrum by controlling the crystal structure and morphology.
“…3c illustrates the schematic and actual fabrication process of GPPbased wLEDs based on the UV chip-on-board (COB) configuration. 43 Zhang et al 44 reported an Eu 2+ -doped silicate SLSAKP GPP, which had a tunable emission band. Gao et al 45 used Al powder to reduce Eu 3+ to Eu 2+ in a SiO 2 -Al 2 O 3 -Na 2 CO 3 -YF 3 -NaF glass matrix.…”
In the past decades, solid-state lighting based on phosphors as energy converters has been a fast-growing industry. Phosphorconverted white light-emitting diodes (pc-wLEDs) enable high-power applications and miniaturization; for this, the phosphor must have good stability and high efficiency. In order to satisfy this demand, phosphor plates have been proposed instead of conventional organic-based phosphor binders. In this review, such phosphor plates are categorized according to their synthesis methods, and the advantages and disadvantages of each category are detailed. In addition, we describe the major aspects of phosphor plates that require improvement for applications in high-power devices. For the fabrication of high-power LEDs, the phosphor configuration, color purity, porosity, and particle size of glass powders are key properties to enhance the luminescence efficiency and reduce the generation of heat inside wLED packages, thereby improving thermal stability. The advent of authentic, energy-efficient lighting in the home and workplace significantly affected the modern way of life. Beginning with the mass production of incandescent light bulbs, and with the subsequent evolution of fluorescence lights, lighting technology has developed rapidly in the last few decades. Since Edison's incandescent bulb in 1879, 1 artificial lighting has been developed to increase power output and decrease the size of the system. The development of red light-emitting diodes (LEDs) in 1962 2 and blue LEDs in 1993 3 allowed innovation in lighting and display. In particular, combinations of blue LEDs and yellow phosphors are used for many applications because they can realize cheap and efficient white solid-state lighting with several advantages including long lifetimes, eco-friendly behavior, and the capacity of miniaturization.
4-6In phosphor-converted white LEDs (pc-wLEDs), the phosphor converter dispersed in silicon resin (phosphor-in-silicon; PiS) is directly packed on a blue InGaN chip.7 When driven by a bias current, the emitted blue light absorbed by the phosphor is emitted as yellow light; together with the transmitted blue light, this constitutes white luminescence. However, this method lacks a red component, which entails the drawbacks of a poor color rendering index (CRI) and limited correlated color temperature (CCT). To overcome these drawbacks, one proposed method mixes yellow phosphors with phosphors having green to red emissions under blue excitation. 8 In pc-wLEDs, the color is primarily determined by the ratio of the blue emission from the LED chip to the yellow to red emission from the phosphor. However, the efficacy and brightness are determined by the converted yellow to red emission, as it contributes the bulk of lumens. In this configuration, the heat generated from the LED chip and phosphor cannot be efficiently dissipated because of the poor thermal stability and weak thermal conductivity of the resin, which causes luminous decay and color shifting in white light-emitting diodes (wLEDs).9 When the tempe...
“…ions doped optical materials for their potential applications in solid-state lighting, laser, plasma display panels (PDP) and non-invasive temperature sensors [1][2][3][4][5]. However, the host materials, where RE 3? ions reside, should be strict selected due to that the radiative/ nonradiative energy transfer of RE 3? ions are highly dependent on the environment surrounding them [6].…”
The luminescent borate glasses co-doped Tb 3? / Eu 3? were successfully synthesized by conventional melting quenching technique. Under 378 nm UV-light excitation, the 542 nm emission intensity of Tb 3? weakened gradually and a shorter decay time was found with increasing the content of Eu 3? concentration, confirming the occurrence of Tb 3? to Eu 3? energy transfer. The luminescent color tunable from pure green to yellow and finally to orange was observed in the Tb 3? /Eu 3? co-doped borate glasses. The fluorescence intensity ratio between the 542 nm of Tb 3? : 5 D 4 ? 7 F 5 transition and 702 nm of Eu 3? : 5 D 0 ? 7 F 4 transition in the luminescent glass was found to be highly temperature-dependent with a good sensitivity of 0.357 % K -1 . Such Tb 3? /Eu 3? co-doped borate glasses may present potential application in solidstate lighting and optical temperature sensors.
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