Radiative and non-radiative decay rate of K2SiF6:Mn4+ phosphors

Kim, Minseuk; Park, Woon Bae; Bang, Bokeuk; Kim, Chang Hae; Sohn, Kee‐Sun

doi:10.1039/c5tc00757g

Cited by 93 publications

(46 citation statements)

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“…Rb 2 TiF 6 :Mn 4+ phosphors, respectively. These values fall in the range of the ever-reported Mn 4+ -activated hexafluorometallate values of ∼3−9 ms at 300 K. 2,6,13,[24][25][26][27][28][29][30][31][32][33] Temperature dependence of PL spectra.-For practical application of the red-emitting phosphors in solid-state lighting system, temperature dependence of the luminescence intensity is very important. Therefore, we measured the PL spectra for the Rb 2 SiF 6 :Mn 4+ and Rb 2 TiF 6 :Mn 4+ phosphors at temperatures between T = 20 and 500 K. Figure 6 shows the results of these measurements.…”

Section: Resultsmentioning

confidence: 99%

Editors' Choice—Rb₂SiF₆:Mn⁴⁺and Rb₂TiF₆:Mn⁴⁺Red-Emitting Phosphors

Sakurai

Nakamura

Adachi

2016

ECS J. Solid State Sci. Technol.

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Rb-based hexafluoride red-emitting phosphors, Rb 2 SiF 6 :Mn 4+ and Rb 2 TiF 6 :Mn 4+ , were synthesized by the coprecipitation method. Optical microscopy observation, X-ray diffraction (XRD) measurement, photoluminescence (PL) analysis, PL excitation (PLE) spectroscopy, and luminescence decay characteristics measurements were used to study the structural and optical properties of the phosphors. The photographs of the bulk samples showed clear crystallographic habits originating from the cubic and trigonal symmetries of the Rb 2 SiF 6 and Rb 2 TiF 6 hosts, respectively, in agreement with the XRD results. The phosphors exhibited an intense narrow-band Mn 4+ ( 2 E g → 4 A 2g ) red emission with internal quantum efficiencies higher than 90% upon blue light excitation. The Franck−Condon analysis of the PLE data yielded the Mn 4+ intra-d-shell transitions to occur at ∼2.47 eV (∼2.34 eV) for the 4 A 2g → 4 T 2g transition and at ∼2.86 eV (∼2.83 eV) for the 4 A 2g → 4 T 1g transition in the Rb 2 SiF 6 :Mn 4+ (Rb 2 TiF 6 :Mn 4+ ) phosphor. Temperature dependence of the PL spectra from T = 20 to 500 K gave the quenching temperature values (T q 's) at which the PL intensity has fallen to half its maximum value to be T q ∼ 490 and ∼450 K for Rb 2 SiF 6 :Mn 4+ . To the best of our knowledge, only one paper has been published on Rb 2 TiF 6 reporting that it crystallizes in the trigonal structure with a = 0.5892 nm and a = 0.4795 nm. Our synthesized phosphors were examined by the X-ray diffraction (XRD) measurement, PL, PLE, and PL decay curve measurements. Temperature dependence of the PL properties was also examined from T = 20 to 500 K in 10-K increments. Efficient sharp red emissions with internal quantum efficiencies larger than 90% were observed from our phosphors that may promise improving a color rendering index of the conventional white-LED lamps.z E-mail: tnakamura@gunma-u.ac.jp; adachi@gunma-u.ac.jp ExperimentalThe rubidium hexafluorometallate phosphors were grown by the coprecipitation method. First, XO 2 (X = Si, Ti) and Rb 2 CO 3 in molar ratio of 1 : 1 were dissolved in an HF solution. Then, KMnO 4 powder was added in the HF solution at 300 K. This mixed solution was left in dark for a few days and resulted in a large single-crystalline phosphor growth (see Fig. 2 below). The resultant bulk single-crystalline phosphors were paper-filtered and dried in room ambient. They were grained in an agate mortar and then used for various measurements.The crystal structures of the synthesized phosphors were examined by performing an XRD analysis using a SmartLab X-ray diffractometer (Rigaku) with Cu Kα radiation at λ = 0.1542 nm. PL measurements were carried out using a single monochromator equipped with a charge-coupled device (Princeton Instruments PIXIS 100) in a CryoMini cryostat (Iwatani Industrial Gases) and a stainless cryostat (Technolo Kogyo) at T = 20 − 500 K in increments of 10 K. A He−Cd laser at λ ex = 325 nm (Kimmon IK3302R-E) was used as the excitation light source.PLE measurements were performed at 300 K...

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Section: Resultsmentioning

confidence: 99%

Editors' Choice—Rb₂SiF₆:Mn⁴⁺and Rb₂TiF₆:Mn⁴⁺Red-Emitting Phosphors

Sakurai

Nakamura

Adachi

2016

ECS J. Solid State Sci. Technol.

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“…[1][2][3][4] Although they exhibit excellent luminescence properties,t heir instability towards moisture has limited their application in WLEDs. [1][2][3][4] Although they exhibit excellent luminescence properties,t heir instability towards moisture has limited their application in WLEDs.…”

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confidence: 99%

Waterproof Alkyl Phosphate Coated Fluoride Phosphors for Optoelectronic Materials

2015

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A facile approach for coating red fluoride phosphors with a moisture-resistant alkyl phosphate layer with a thickness of 50-100 nm is reported. K2 SiF6 :Mn(4+) particles were prepared by co-precipitation and then coated by esterification of P2 O5 with alcohols (methanol, ethanol, and isopropanol). This route was adopted to encapsulate the prepared phosphors using transition-metal ions as cross-linkers between the alkyl phosphate moieties. The coated phosphor particles exhibited a high water tolerance and retained approximately 87 % of their initial external quantum efficiency after aging under high-humidity (85 %) and high-temperature (85 °C) conditions for one month. Warm white-light-emitting diodes that consisted of blue InGaN chips, the prepared K2 SiF6 :Mn(4+) phosphors, and either yellow Y3 Al5 O12 :Ce(3+) phosphors or green β-SiAlON: Eu(2+) phosphors showed excellent color rendition.

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“…4). 25 In this process, there occurs a difference in the velocity of photons (or number) excited and the velocity of photons (or number) emitted, so that a relaxation process cannot be performed to the 4f 1 (2F 7/2 ) ground state and accumulation occurs in the 4f 0 5d 1 excited state. Luminescence saturation means that the optical efficiency drops when the number of accumulated photons (N accum ) exceeds the intrinsic N MAP of the phosphor, or when the number of photons excited by the 4f 0 5d 1 excited state exceeds the N MAP .…”

Section: Resultsmentioning

confidence: 99%

“…To verify the number of maximum acceptable photons (N MAP ) for each phosphor, a In addition, to clearly distinguish the effects of self-heating of non-radiative recombination, the YAG was measured in CW mode and pulsed mode, respectively. 22,25 Light source irradiated in pulsed mode was excited with a frequency of 3.57 Hz to prevent photons from accumulating due to long decay time and thereby self-heating, as shown in Fig. 3.…”

Section: Methodsmentioning

confidence: 99%

Luminescence Saturation in Inorganic Phosphors under High Flux of Photon Excitation

Ahn¹,

Park²,

Lim³

et al. 2018

ECS J. Solid State Sci. Technol.

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The luminescence behavior of certain phosphor material shows non-linearity within a specific photon excitation range, depending upon the activator and/or the host lattice. Conventionally, the absorption and emission characteristics of phosphors are measured using a spectrometer with a light source such as a xenon lamp. Herein, a new measurement system was set up to investigate luminescence saturation in inorganic phosphors. The effect of the environment on the longevity of the material has been examined for each attribute and the conditions for luminescence saturation have been discussed. © The Author(s) 2018. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives 4.0 License (CC BY-NC-ND, http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial reuse, distribution, and reproduction in any medium, provided the original work is not changed in any way and is properly cited. For permission for commercial reuse, please email: oa@electrochem.org. Phosphor-converted white light-emitting diodes (pc-WLEDs) are widely used as a light source in liquid crystal displays and in solidstate lighting. They are known to be more stable than Ne-, fluorescent-, and halogen-lamps. In addition, they exhibit an excellent efficiency of ∼246 lm/W at 20 mA. The pc-WLEDs directly convert electrical energy into light. [1][2][3][4] In this conversion process, some electrical energy is dissipated in the form of heat, which leads to a decrease in the light efficiency. Heat sinks and cooling fans are also sources of LED power consumption that lead to a non-negligible decline in the lighting efficiency. 5,6 As the applications of high-power pc-WLEDs continue to increase, ensuring the reliability of these devices in terms of their optical characteristics and thermal stability has gained importance. In particular, a decrease in the efficiency of the power output and life-time has also been reported. 7,8 As the current density of the pc-WLEDs increases, their light output also increases and more heat is emitted. [9][10][11] It is known that the heat generated in the device increases the temperature of the active region of the quantum-well (QW) layer in the LED structure. The elevated temperature may also decrease the bandgap of the active region, which would cause the generation of more heat due to non-radiative recombination in the active region. This positive feedback process reduces the quantum efficiency of the LED and eventually causes degradation of its luminance and lifetime. 12 However, a more commonly encountered phenomenon is droop, in which the efficiency decreases over a certain level as the output increases. Although many studies have focused on clarifying the cause of the droop phenomenon and implicated sources such as carrier heating, carrier escape, and the Auger effect, the exact cause has not been identified as yet. [13][14][15][16] Therefore, further detailed studies are necessary. In general, the reliability of pc-WLE...

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Radiative and non-radiative decay rate of K₂SiF₆:Mn⁴⁺ phosphors

Abstract: Mn4+-activated K2SiF6 phosphors for use in light emitting diode (LED) applications have recently attracted a great deal of attention since they exhibit an advantage over conventional wide band-type red-light-emitting phosphors.

Cited by 93 publications

References 22 publications

Editors' Choice—Rb₂SiF₆:Mn⁴⁺and Rb₂TiF₆:Mn⁴⁺Red-Emitting Phosphors

Editors' Choice—Rb₂SiF₆:Mn⁴⁺and Rb₂TiF₆:Mn⁴⁺Red-Emitting Phosphors

Waterproof Alkyl Phosphate Coated Fluoride Phosphors for Optoelectronic Materials

Luminescence Saturation in Inorganic Phosphors under High Flux of Photon Excitation

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Radiative and non-radiative decay rate of K2SiF6:Mn4+ phosphors

Abstract: Mn4+-activated K2SiF6 phosphors for use in light emitting diode (LED) applications have recently attracted a great deal of attention since they exhibit an advantage over conventional wide band-type red-light-emitting phosphors.

Cited by 93 publications

References 22 publications

Editors' Choice—Rb2SiF6:Mn4+and Rb2TiF6:Mn4+Red-Emitting Phosphors

Editors' Choice—Rb2SiF6:Mn4+and Rb2TiF6:Mn4+Red-Emitting Phosphors

Waterproof Alkyl Phosphate Coated Fluoride Phosphors for Optoelectronic Materials

Luminescence Saturation in Inorganic Phosphors under High Flux of Photon Excitation

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Radiative and non-radiative decay rate of K₂SiF₆:Mn⁴⁺ phosphors

Editors' Choice—Rb₂SiF₆:Mn⁴⁺and Rb₂TiF₆:Mn⁴⁺Red-Emitting Phosphors

Editors' Choice—Rb₂SiF₆:Mn⁴⁺and Rb₂TiF₆:Mn⁴⁺Red-Emitting Phosphors