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M G Brik - One of the best experts on this subject based on the ideXlab platform.
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mn4 doped heterodialkaline fluorogermanate Red phosphor with high quantum yield and spectral luminous efficacy for warm white light emitting device application
Inorganic Chemistry, 2018Co-Authors: Chunyan Jiang, Mingying Peng, Alok M. Srivastava, M G BrikAbstract:Narrow band Red-emitting Mn4+-doped fluoride phosphor is an essential Red Component of modern white-light-emitting-diode (WLED) devices. Its luminescence has sensitivity to structure and influences the performance of WLED. In this paper, we report a high-performance Mn4+ phosphor based on a new heterodialkaline fluorogermanate, CsNaGeF6:Mn4+. As determined by the single-crystal X-ray diffraction analysis, the CsNaGeF6 compound crystallizes in the orthorhombic crystal system with space group Pbcm (No. 57). Under excitation by 360 and 470 nm photons, CsNaGeF6:Mn4+ emits intense Red light near 630 nm with a high quantum yield of 95.6%. The electronic energy levels of the Mn4+ ion in Cs2GeF6, Na2GeF6, and CsNaGeF6 are calculated using the exchange charge model of crystal-field theory. The local Mn4+ environment inducing different zero-phonon-line emissions in the structures is probed by electron paramagnetic resonance. The Mn4+-doped heterodialkaline fluorogermanate CsNaGeF6:Mn4+ exhibits broader emission as ...
Mingying Peng - One of the best experts on this subject based on the ideXlab platform.
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mn4 doped heterodialkaline fluorogermanate Red phosphor with high quantum yield and spectral luminous efficacy for warm white light emitting device application
Inorganic Chemistry, 2018Co-Authors: Chunyan Jiang, Mingying Peng, Alok M. Srivastava, M G BrikAbstract:Narrow band Red-emitting Mn4+-doped fluoride phosphor is an essential Red Component of modern white-light-emitting-diode (WLED) devices. Its luminescence has sensitivity to structure and influences the performance of WLED. In this paper, we report a high-performance Mn4+ phosphor based on a new heterodialkaline fluorogermanate, CsNaGeF6:Mn4+. As determined by the single-crystal X-ray diffraction analysis, the CsNaGeF6 compound crystallizes in the orthorhombic crystal system with space group Pbcm (No. 57). Under excitation by 360 and 470 nm photons, CsNaGeF6:Mn4+ emits intense Red light near 630 nm with a high quantum yield of 95.6%. The electronic energy levels of the Mn4+ ion in Cs2GeF6, Na2GeF6, and CsNaGeF6 are calculated using the exchange charge model of crystal-field theory. The local Mn4+ environment inducing different zero-phonon-line emissions in the structures is probed by electron paramagnetic resonance. The Mn4+-doped heterodialkaline fluorogermanate CsNaGeF6:Mn4+ exhibits broader emission as ...
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The electronic and optical properties of a narrow-band Red-emitting nanophosphor K2NaGaF6:Mn4+ for warm white light-emitting diodes
Journal of Materials Chemistry C, 2018Co-Authors: Chunyan Jiang, Mikhail G. Brik, Jie Peng, Maxim S. Molokeev, Ka-leung Wong, Mingying PengAbstract:Recently, as a key Red Component in the development of warm white light-emitting diodes (WLEDs), Mn4+-doped fluorides with narrow Red emission have sparked rapidly growing interest because they improve color rendition and enhance the visual energy efficiency. Herein, a Red nanophosphor, K2NaGaF6:Mn4+, with a diameter of 150–250 nm has been synthesized using a simple co-precipitation method. Rietveld refinement reveals that it crystallizes in the space group Fmm with the cell parameter a = 8.25320(4) A. The exchange charge model (ECM) has been used to calculate the energy levels of Mn4+ ions in K2NaGaF6, which match well with the experimental spectra. The as-synthesized phosphor exhibits a narrow Red emission at around 630 nm (spin-forbidden 2Eg → 4A2 transition of Mn4+ ions) when excited at 365 nm (4A2g → 4T1g) and 467 nm (4A2g → 4T2g), with a quantum efficiency (QE) of 61% and good resistance to thermal quenching. Based on the structure, the formation mechanism of ZPL has been discussed. In addition, the concentration-dependent decay curves of Mn4+ in K2NaGaF6 were fitted using the Inokuti–Hirayama model, suggesting that the dipole–dipole interactions determine the concentration quenching. Finally, encouraged by the good performance, a warm LED with a CRI of 89.4 and CCT of 3779 K was fabricated by employing the title nanophosphor as the Red Component. Our findings suggest that K2NaGaF6:Mn4+ can be a viable candidate for the Red phosphor used in warm WLEDs.
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Mn4+-Doped Heterodialkaline Fluorogermanate Red Phosphor with High Quantum Yield and Spectral Luminous Efficacy for Warm-White-Light-Emitting Device Application
2018Co-Authors: Chunyan Jiang, Mingying Peng, Alok M. Srivastava, Mikhail G. BrikAbstract:Narrow band Red-emitting Mn4+-doped fluoride phosphor is an essential Red Component of modern white-light-emitting-diode (WLED) devices. Its luminescence has sensitivity to structure and influences the performance of WLED. In this paper, we report a high-performance Mn4+ phosphor based on a new heterodialkaline fluorogermanate, CsNaGeF6:Mn4+. As determined by the single-crystal X-ray diffraction analysis, the CsNaGeF6 compound crystallizes in the orthorhombic crystal system with space group Pbcm (No. 57). Under excitation by 360 and 470 nm photons, CsNaGeF6:Mn4+ emits intense Red light near 630 nm with a high quantum yield of 95.6%. The electronic energy levels of the Mn4+ ion in Cs2GeF6, Na2GeF6, and CsNaGeF6 are calculated using the exchange charge model of crystal-field theory. The local Mn4+ environment inducing different zero-phonon-line emissions in the structures is probed by electron paramagnetic resonance. The Mn4+-doped heterodialkaline fluorogermanate CsNaGeF6:Mn4+ exhibits broader emission as a result of the lowest symmetry. It has higher quantum yield than Na2GeF6:Mn4+ and higher spectral luminous efficacy than Cs2GeF6:Mn4+. Given the good thermal stability and efficient luminescence, a prototype warm-WLED device with a color rendering index of 92.5, a correlated color temperature of 3783 K, and a luminous efficacy of 176.3 lm/W has been fabricated by employing the CsNaGeF6:Mn4+ phosphor as the Red Component. Our results not only reveal that a high-performance Mn4+ Red phosphor is achieved through cationic substitutions but also construct a relationship of performance–structure to guide the design of Mn4+ phosphors in the future
Chunyan Jiang - One of the best experts on this subject based on the ideXlab platform.
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mn4 doped heterodialkaline fluorogermanate Red phosphor with high quantum yield and spectral luminous efficacy for warm white light emitting device application
Inorganic Chemistry, 2018Co-Authors: Chunyan Jiang, Mingying Peng, Alok M. Srivastava, M G BrikAbstract:Narrow band Red-emitting Mn4+-doped fluoride phosphor is an essential Red Component of modern white-light-emitting-diode (WLED) devices. Its luminescence has sensitivity to structure and influences the performance of WLED. In this paper, we report a high-performance Mn4+ phosphor based on a new heterodialkaline fluorogermanate, CsNaGeF6:Mn4+. As determined by the single-crystal X-ray diffraction analysis, the CsNaGeF6 compound crystallizes in the orthorhombic crystal system with space group Pbcm (No. 57). Under excitation by 360 and 470 nm photons, CsNaGeF6:Mn4+ emits intense Red light near 630 nm with a high quantum yield of 95.6%. The electronic energy levels of the Mn4+ ion in Cs2GeF6, Na2GeF6, and CsNaGeF6 are calculated using the exchange charge model of crystal-field theory. The local Mn4+ environment inducing different zero-phonon-line emissions in the structures is probed by electron paramagnetic resonance. The Mn4+-doped heterodialkaline fluorogermanate CsNaGeF6:Mn4+ exhibits broader emission as ...
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The electronic and optical properties of a narrow-band Red-emitting nanophosphor K2NaGaF6:Mn4+ for warm white light-emitting diodes
Journal of Materials Chemistry C, 2018Co-Authors: Chunyan Jiang, Mikhail G. Brik, Jie Peng, Maxim S. Molokeev, Ka-leung Wong, Mingying PengAbstract:Recently, as a key Red Component in the development of warm white light-emitting diodes (WLEDs), Mn4+-doped fluorides with narrow Red emission have sparked rapidly growing interest because they improve color rendition and enhance the visual energy efficiency. Herein, a Red nanophosphor, K2NaGaF6:Mn4+, with a diameter of 150–250 nm has been synthesized using a simple co-precipitation method. Rietveld refinement reveals that it crystallizes in the space group Fmm with the cell parameter a = 8.25320(4) A. The exchange charge model (ECM) has been used to calculate the energy levels of Mn4+ ions in K2NaGaF6, which match well with the experimental spectra. The as-synthesized phosphor exhibits a narrow Red emission at around 630 nm (spin-forbidden 2Eg → 4A2 transition of Mn4+ ions) when excited at 365 nm (4A2g → 4T1g) and 467 nm (4A2g → 4T2g), with a quantum efficiency (QE) of 61% and good resistance to thermal quenching. Based on the structure, the formation mechanism of ZPL has been discussed. In addition, the concentration-dependent decay curves of Mn4+ in K2NaGaF6 were fitted using the Inokuti–Hirayama model, suggesting that the dipole–dipole interactions determine the concentration quenching. Finally, encouraged by the good performance, a warm LED with a CRI of 89.4 and CCT of 3779 K was fabricated by employing the title nanophosphor as the Red Component. Our findings suggest that K2NaGaF6:Mn4+ can be a viable candidate for the Red phosphor used in warm WLEDs.
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Mn4+-Doped Heterodialkaline Fluorogermanate Red Phosphor with High Quantum Yield and Spectral Luminous Efficacy for Warm-White-Light-Emitting Device Application
2018Co-Authors: Chunyan Jiang, Mingying Peng, Alok M. Srivastava, Mikhail G. BrikAbstract:Narrow band Red-emitting Mn4+-doped fluoride phosphor is an essential Red Component of modern white-light-emitting-diode (WLED) devices. Its luminescence has sensitivity to structure and influences the performance of WLED. In this paper, we report a high-performance Mn4+ phosphor based on a new heterodialkaline fluorogermanate, CsNaGeF6:Mn4+. As determined by the single-crystal X-ray diffraction analysis, the CsNaGeF6 compound crystallizes in the orthorhombic crystal system with space group Pbcm (No. 57). Under excitation by 360 and 470 nm photons, CsNaGeF6:Mn4+ emits intense Red light near 630 nm with a high quantum yield of 95.6%. The electronic energy levels of the Mn4+ ion in Cs2GeF6, Na2GeF6, and CsNaGeF6 are calculated using the exchange charge model of crystal-field theory. The local Mn4+ environment inducing different zero-phonon-line emissions in the structures is probed by electron paramagnetic resonance. The Mn4+-doped heterodialkaline fluorogermanate CsNaGeF6:Mn4+ exhibits broader emission as a result of the lowest symmetry. It has higher quantum yield than Na2GeF6:Mn4+ and higher spectral luminous efficacy than Cs2GeF6:Mn4+. Given the good thermal stability and efficient luminescence, a prototype warm-WLED device with a color rendering index of 92.5, a correlated color temperature of 3783 K, and a luminous efficacy of 176.3 lm/W has been fabricated by employing the CsNaGeF6:Mn4+ phosphor as the Red Component. Our results not only reveal that a high-performance Mn4+ Red phosphor is achieved through cationic substitutions but also construct a relationship of performance–structure to guide the design of Mn4+ phosphors in the future
H. Nagabhushana - One of the best experts on this subject based on the ideXlab platform.
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Monovalent ions co-doped SrTiO3:Pr3+ nanostructures for the visualization of latent fingerprints and can be Red Component for solid state devices
Journal of Luminescence, 2019Co-Authors: S. Yeshodamma, D.v. Sunitha, R.b. Basavaraj, G.p. Darshan, B. Daruka Prasad, H. NagabhushanaAbstract:Abstract Structural and luminescence properties of SrTiO3: Pr3+: A+ (A+: Li, Na, K) nanophosphors were synthesized by simple sonochemical route. PrepaRed products were well-characterized for their optical and structural properties. Surface morphology of the prepaRed samples were studied with the influential parameters such as surfactant concentration, sonication time, temperature, pH and compaRed the effect with normal mechanical stirring. Morphology was highly dependent on the experimental parameters. The pRedicted growth mechanism to obtain superstructures of the samples prepaRed by sonochemical method was discussed. Photoluminescence (PL) studies exhibit characteristic emission peaks of Pr3+ ions in the range 500–750 nm. The highest PL intensity was obtained for 5 mol% of Pr3+ doped samples. Further, co-doping with Li+, Na+ and K+ ions into Pr3+ activated SrTiO3 phosphor led to an enhancement in luminescence intensity by Reducing the parity restriction of electric dipole transitions. As a consequence of suitable local distortion of the crystal field surrounding to the Pr3+ activator ions. The maximum PL intensity was observed for Li+ (1 wt%) co-doped SrTiO3:Pr3+ (5 mol%) samples. Furthermore, Li+ ion was the best charge compensator, because of it Reduced the defects emission and also increased the emission intensity of Pr3+ significantly. PrepaRed phosphors exhibit short lifetime, good quantum efficiency; excellent color purity which is near to the NTSC standards. PrepaRed fluorescent powders were used as a dusting powder for the rapid visualization of latent fingerprints under UV light of 254 nm. From the reported results it is evident that the optimized prepaRed samples are suitable for solid state lighting and advanced forensic investigation applications.
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surfactant assisted batio3 eu3 sio2 core shell superstructures obtained by ultrasonication method dormant fingerprint visualization and Red Component of white light emitting diode applications
ACS Sustainable Chemistry & Engineering, 2018Co-Authors: Dhanalakshmi Muniswamy, H. Nagabhushana, R.b. Basavaraj, G.p. Darshan, Daruka Prasad BAbstract:Nanoparticles (NPs) synthesized via a facile sonochemical route showed excellent assembly of BaTiO3:Eu3+@SiO2 superstructures (SS) using CTAB as a surfactant. Crystallite size, phase, surface science, and core–shell confirmation were determined through advanced characterization techniques. Experimental parameters like pH, temperature, and surfactant concentration were varied and resulted in SS with high surface modifications, and the possible mechanisms for the same are reported. Scanning electron microscopy images revealed broomlike structures, and various experimental parameters resulting in them dissolving into freestanding sticks are discussed. CIE chromaticity coordinates were in the range of the orange-Red to pure Red. Drawbacks associated with the commercial powder dusting method for visualizing dormant fingerprint (DFP), namely, high background scattering and high autofluorescence of the substrate material, were improved with the help of the prepaRed SS as a dusting powder. Visualization of DFPs a...
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Synthesis, structure and photoluminescence properties of Sm3+-doped BiOBr phosphor
2016Co-Authors: Pramod Halappa, C. Shivakumara, Rohit Saraf, H. NagabhushanaAbstract:Well-crystallized tetragonal layeRed BiOBr and Bi0.95Sm0.05OBr phosphors were prepaRed by the solid state method. These compounds were characterized using powder X-Ray diffraction and photoluminescence technique. In PL spectra, the electric dipole transitions dominate than other transitions which indicate that the Sm3+ ions occupy a site with an inversion center of BiOBr. CIE chromaticity diagram confirmed that these phosphors can be useful in the fabrication of Red Component in white light emitting diodes (WLEDs) for display device applications.
Jung Hyun Jeong - One of the best experts on this subject based on the ideXlab platform.
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Simultaneous realization of two approaches to white light in single-Component phosphors.
Optics Express, 2014Co-Authors: Lili Wang, Byung Kee Moon, Sung Heum Park, Jung Hyun JeongAbstract:A novel single-Component warm white light-emitting Sr2Ca0.995MoO6: Sm3+0.005 phosphor was synthesized by solid-state reaction. The photoluminescence excitation spectra ranging from 300 to 450 nm and 460 to 500 nm broadly are observed. Direct full-color warm white light [(x, y) = 0.3221, 0.3525] was realized in this single-phase phosphor with exposure to 380 nm UV light. When this phosphor is pumped by 466 nm radiation we obtained yellow emission with an intense Red Component, suggesting that this material is also competitive as a blue-pumped yellow phosphor. Thus two approaches to white light are realized simultaneously in Sm3+ doped single-Component phosphor for the first time. The quantum yield and the reliability of the as-synthesized phosphors for White LED applications were also investigated.