Discovery of novel phosphors for use in light emitting diodes using heuristics optimization-assisted combinatorial chemistry

Son, Kyung Hyun; Singh, Satendra Pal; Sohn, Kee‐Sun

doi:10.1039/c2jm30280b

Cited by 15 publications

(9 citation statements)

References 26 publications

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“…1−4 The other is to find new host materials by analyzing single crystals 5−7,11,13−18 or powder products. 12,19,20 In the single-crystal analysis, a large-size crystal (typically larger than 100 μm in all dimensions) is necessary to determine the crystal structure. Growing the crystal is a time-intensive process, especially for materials with high melting temperatures or no liquid phase.…”

Section: ■ Introductionmentioning

confidence: 99%

“…One is to investigate known crystal structures that are suitable for luminescent center doping and are not studied to be host crystals. [1][2][3][4] The other is to find new host materials by analyzing single crystals [5][6][7]11,[13][14][15][16][17][18] or powder products 12,19,20 . In the single crystal analysis, a large-size crystal (typically larger than 100 μm in all dimensions) is necessary to determine the crystal structure.…”

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confidence: 99%

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Narrow-Band Green-Emitting Phosphor Ba₂LiSi₇AlN₁₂:Eu²⁺ with High Thermal Stability Discovered by a Single Particle Diagnosis Approach

et al. 2015

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The narrow-band green-emitting phosphor Ba 2 LiSi 7 AlN 12 :Eu 2+ was discovered by analyzing a single particle in a powder mixture, which we call the Single Particle Diagnosis Approach. Single crystal X-ray diffraction (XRD) analysis of the particle revealed that Ba 2 LiSi 7 AlN 12 :Eu 2+ crystallizes in the Pnnm space group (No. 58) with a = 14.0941 Å, b = 4.8924 Å, c = 8.0645 Å, and Z = 2. The crystal structure is composed of a corner-sharing (Si,Al)N 4 corrugated layer and edge-sharing (Si,Al)N 4 and LiN 4 tetrahedra. Ba(Eu) occupies the one-dimensional channel in a zigzag manner. The luminescence properties were also measured using a single crystalline particle. Ba 2 LiSi 7 AlN 12 :Eu 2+ shows a green luminescence peak at approximately 515 nm with a narrow full-width at half-maximum (FWHM) of 61 nm. It shows high quantum efficiency (QE) of 79 % with 405-nm excitation and a small decrease of luminescence intensity, even at 300 °C.

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Section: ■ Introductionmentioning

confidence: 99%

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confidence: 99%

Narrow-Band Green-Emitting Phosphor Ba₂LiSi₇AlN₁₂:Eu²⁺ with High Thermal Stability Discovered by a Single Particle Diagnosis Approach

et al. 2015

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“…Recently, solid-state combinatorial synthesis based on heuristic optimization techniques has proven to be a very effective tool for the discovery of novel phosphors for application in WLEDs, and our group has successfully discovered several novel phosphors using these techniques. − In the present study, a similar approach was adopted in the search for a novel red-emitting phosphor host in the alkali-germanate system composed of the A–Ge–O (A = Li, K, Rb) system and doped with a small amount of Mn 4+ ions. All the phases obtained during the synthesis were qualitatively and quantitatively characterized using powder X-ray diffraction, and the luminescent behavior was systematically studied using photoluminescent measurements.…”

Section: Introductionmentioning

confidence: 99%

Discovery of a Red-Emitting Li₃RbGe₈O₁₈:Mn⁴⁺ Phosphor in the Alkali-Germanate System: Structural Determination and Electronic Calculations

et al. 2016

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A solid-state combinatorial chemistry approach, which used the A-Ge-O (A = Li, K, Rb) system doped with a small amount of Mn as an activator, was adopted in a search for novel red-emitting phosphors. The A site may have been composed of either a single alkali metal ion or of a combination of them. This approach led to the discovery of a novel phosphor in the above system with the chemical formula LiRbGeO:Mn. The crystal structure of this novel phosphor was solved via direct methods, and subsequent Rietveld refinement revealed a trigonal structure in the P3̅1m space group. The discovered phosphor is believed to be novel in the sense that neither the crystal structure nor the chemical formula matches any of the prototype structures available in the crystallographic information database (ICDD or ICSD). The measured photoluminescence intensity that peaked at a wavelength of 667 nm was found to be much higher than the best intensity obtained among all the existing AGeO (A = Li, K, Rb) compounds in the alkali-germanate system. An ab initio calculation based on density function theory (DFT) was conducted to verify the crystal structure model and compare the calculated value of the optical band gap with the experimental results. The optical band gap obtained from diffuse reflectance measurement (5.26 eV) and DFT calculation (4.64 eV) results were in very good agreement. The emission wavelength of this phosphor that exists in the deep red region of the electromagnetic spectrum may be very useful for increasing the color gamut of LED-based display devices such as ultrahigh-definition television (UHDTV) as per the ITU-R BT.2020-2 recommendations and also for down-converter phosphors that are used in solar-cell applications.

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“…A material with the composition Y 0.845 Al 0.07 La 0.06 VO 4 was obtained, which was claimed to have a favorable color point for display applications. Several reports on the preparation of phosphor libraries and the discovery of new luminescent materials or different compositions followed . A promising yellow‐emitting phosphor discovered by combinatorial synthesis is La 4‐x Ca x Si 12 O 3+x N 18‐x :Eu 2+ .…”

Section: Discovery Of New Phosphorsmentioning

confidence: 99%

Photoluminescent Materials for Solid‐State Lighting: State of the Art and Future Challenges

Meyer

Tappe

2015

Advanced Optical Materials

198

110

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• Control over purity and particle morphology.• Non-hazardous.• Reasonable production costs.While for certain conversion colors solutions close to the ideal have been found, there remains work to be done, especially for phosphors which emit in the red. This article will highlight the classic solutions for white pcLEDs and show the remaining challenges. In addition, an account will be given of recent developments involving semiconductor light sources with high radiance and high lumen output, where the color conversion of blue laser diodes for digital projection and automotive applications poses new challenges to materials research. Luminescent Materials: The State of the Art Yellow-Emitting MaterialsToday, almost all single-phosphor pcLEDs are based on Ce 3+ -doped yttrium aluminum garnet (Y 3 Al 5 O 12 , YAG:Ce) [ 5,6 ] or, sometimes, Eu 2+ -doped orthosilicate phosphors (Sr, Ba, Mg) 2 SiO 4 , [7][8][9][10][11][12][13] as the yellow-emitting luminescent material. However, stability issues of the orthosilicates have not been fully overcome: this has limited the commercial use of this material class.The emission color of YAG:Ce can be tuned by substitution of lattice constituents, e.g., Y may be replaced by Lu (Lutetium), Gd (Gadolinium), or Tb (Terbium), and Al may be replaced by Ga (Gallium). The emission spectrum is shown in Figure 1 . This material fulfi lls all of the stated requirements and therefore can be considered an archetypal LED phosphor material. [ 14,15 ] The excitation spectrum for YAG:Ce at 440-460 nm is well matched to the emission of blue LEDs and its yellow dual ground-state broadband emission in the visible spectral region (500-700 nm) provides a reasonable CRI. Such a single-phosphor approach may be very simple and effi cient, but it has one major drawback: the limited spectral power distribution in the red spectral range causes a CCT > 4000 K (cool white light) and a low CRI (usually below 80). Particularly for indoor illumination, a higher CRI and lower (i.e., warmer) CCT (2700-3200 K) are preferable. Suitable white light LEDs can be produced using a two-phosphor approach, wherein a yellow phosphor (YAG:Ce) is combined with a red one.The effi cient generation of white light by phosphor-converted LEDs (pcLEDs) suffers from a trade-off between high color rendition, low correlated color temperatures, and luminous effi cacy. While this is partially an inherent problem, it is also caused by the spectral effi ciency of the materials used. The particular challenges for materials research lie, amongst the demanding general requirements, in fi nding very narrow-band or line-emitting materials: excitable with blue light, emitting in the near red. A way to design Mn(IV) activated line emitters is proposed, and methods for high-throughput combinatorial syntheses are specifi ed.

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Discovery of novel phosphors for use in light emitting diodes using heuristics optimization-assisted combinatorial chemistry

Cited by 15 publications

References 26 publications

Narrow-Band Green-Emitting Phosphor Ba₂LiSi₇AlN₁₂:Eu²⁺ with High Thermal Stability Discovered by a Single Particle Diagnosis Approach

Narrow-Band Green-Emitting Phosphor Ba₂LiSi₇AlN₁₂:Eu²⁺ with High Thermal Stability Discovered by a Single Particle Diagnosis Approach

Discovery of a Red-Emitting Li₃RbGe₈O₁₈:Mn⁴⁺ Phosphor in the Alkali-Germanate System: Structural Determination and Electronic Calculations

Photoluminescent Materials for Solid‐State Lighting: State of the Art and Future Challenges

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Discovery of novel phosphors for use in light emitting diodes using heuristics optimization-assisted combinatorial chemistry

Cited by 15 publications

References 26 publications

Narrow-Band Green-Emitting Phosphor Ba2LiSi7AlN12:Eu2+ with High Thermal Stability Discovered by a Single Particle Diagnosis Approach

Narrow-Band Green-Emitting Phosphor Ba2LiSi7AlN12:Eu2+ with High Thermal Stability Discovered by a Single Particle Diagnosis Approach

Discovery of a Red-Emitting Li3RbGe8O18:Mn4+ Phosphor in the Alkali-Germanate System: Structural Determination and Electronic Calculations

Photoluminescent Materials for Solid‐State Lighting: State of the Art and Future Challenges

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Narrow-Band Green-Emitting Phosphor Ba₂LiSi₇AlN₁₂:Eu²⁺ with High Thermal Stability Discovered by a Single Particle Diagnosis Approach

Narrow-Band Green-Emitting Phosphor Ba₂LiSi₇AlN₁₂:Eu²⁺ with High Thermal Stability Discovered by a Single Particle Diagnosis Approach

Discovery of a Red-Emitting Li₃RbGe₈O₁₈:Mn⁴⁺ Phosphor in the Alkali-Germanate System: Structural Determination and Electronic Calculations