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Thick‐film phosphor‐in‐glasses (PiGs) were fabricated via a screen‐printing method with various phosphor layer structures, to compose a white light emitting diode (LED). Green (Lu3Al5O12:Ce3+) and red (CaAlSiN3:Eu2+) phosphors were mixed, layered, and patterned on a glass substrate. The chromaticity of each structured PiG was tuned to achieve a white LED by varying phosphor content and thickness. The emission spectra and the related various color conversion properties, including color coordinates, correlated color temperature (CCT), color rendering index (CRI), luminous efficacy (LE) and the color gamut of the mounted PiGs with different phosphor layer structures were examined and compared. Time‐resolved photoluminescence (TRPL) measurements of the white LEDs with various phosphor layer structural designs were also obtained and compared. It was observed that spectral variation depended on the PiG layer structure. A proper PiG layer structural design was discussed for practical applications. [ABSTRACT FROM AUTHOR]

Quantum dot embedded glasses (QDEGs) were prepared by the conventional melt‐quenching method to enhance its color conversion efficiency via optimizing the concentration of ZnS, ZnSe, and CdO within the silicate‐based glass matrix. The QDEG, which contained 0.875 ZnS, 0.625 ZnSe, and 0.75 CdO (in mol%) and was heat treated at 500°C for 10 hours showed promising color conversion with an improved quantum yield of up to 25%. Color coordination of light‐emitting diodes (LEDs) mounted with the QDEGs could be adjusted by tuning heat‐treatment conditions and thickness control of QDEGs. The practical feasibility of the QDEG for a white LED is demonstrated with a reasonable glass thickness for LED packaging process. The formation of Cd‐S‐Se quantum dots within a glass matrix was identified by Raman and HR‐TEM analyses. The effect of ZnSe and CdO on the formation of Cd‐S‐Se quantum dots within silicate glass is also discussed. [ABSTRACT FROM AUTHOR]

A low sintering temperature glass based on the SiO2-P2O5-ZnO-B2O3-R2O (R=K and Na) system was studied as a matrix for embedding phosphors to fabricate color tunable white LEDs. The proposed system, which uses no heavy-metal elements and can be sintered at 500°C, incorporates thermally weak commercial phosphors such as CaAlSiN3:Eu2+ to produce phosphor-in-glasses (PiGs). Changing the mixing ratio of glass to phosphors affected the photo-luminescence spectra and color coordinates of the PiGs when mounted on a blue LED. The color rendering index (CRI) and color correlated temperature (CCT) of the LEDs were also varied with the mixing ratio, providing color tunable white LEDs. A high CRI, up to 93, as well as highly improved thermal stability were obtained, along with a low sintering temperature compared to other glass systems, suggesting the practical feasibility of the proposed system. [ABSTRACT FROM AUTHOR]

Fluorescent glass frits were prepared and used to synthesize phosphor-in-fluorescent glass composites (PiFGs) to realize stable white light emitting diodes with high color-rendering properties. Commercial red, green, and blue phosphors were co-sintered and red phosphors were partially replaced by Eu3+ in glass frits. Phosphor-in-glass composites were placed on UV-light emitting diodes ( UV- LEDs) to generate white light. Pure white light with a luminous efficacy=58.4 lm/W, general color rendering index Ra=87 and special color rendering index for strong red R9=73 was realized with glass frits containing 7 mol% Eu2O3 and RGB ratio of 35:20:15. Luminous efficacy, Ra and R9 increased as red phosphors were replaced by red-fluorescent glass frits. [ABSTRACT FROM AUTHOR]

Phosphor-in-glass (PiG) thick film was fabricated on a borosilicate glass substrate using a conventional screen printing method and employing phosphosilicate glass to allow low-temperature sintering. The vehicle content and sintering temperature were optimized to form a thick film with a thickness of ~50 μm. Commercial yellow (Y3Al5O12:Ce3+) and red (CaAlSiN3:Eu2+) phosphors were successfully incorporated within the glass matrix and then sintered at 550°C. Color-tunable white LEDs were achieved using the PiG thick films as a color converter by varying the glass to phosphor (GtP) ratio. The high luminous efficacy of up to ~120 lm/W and high color rendering index of up to 89 in combination with the thermal quenching property prove the practical feasibility of the PiG thick films for high-power/high-brightness LED applications. [ABSTRACT FROM AUTHOR]

Commercial Ce3+: YAG phosphors were embedded in glass frits. Thermal condition for the viscous sintering of the composite materials was optimized. The phosphor-glass composites had maximum external efficiency of 30% and maximum light extraction efficiency of 39%. Color temperatures of the composites composed of fluorescent glass frits containing Eu3+ and Mn2+ combined with blue LEDs shifted from ~7000 to ~4000 K. [ABSTRACT FROM AUTHOR]

Pr3+ singly doped SiO 2 –Na 2 O–Al 2 O 3 –LaF 3 glass ceramics were fabricated as an inorganic color converter with wide color gamut for white light emitting diodes (wLEDs). Under 450 nm LED excitation, the simultaneous photo-luminescence (PL) emissions of green at 502 nm due to the Pr3+:3P 1 →3H 4 transition and red at 613 and 643 nm due to Pr3+:3P 0 →3H 6 and 3P 0 →3F 2 , respectively, were observed. Before heat treatment, the PL intensity of the green and red emissions were limited relative to that of the blue electroluminescence (EL), due to the high transparency of the glass. This was highly improved by the crystallization of the glass with heat treatment. PrF 3 concentration and heat treatment conditions such as temperature and duration time were varied to adjust the relative intensity of blue (EL), green and red (PL). The formation of LaF 3 crystals within the glass ceramic and their effect on the visible spectra are discussed. The glass ceramics were mounted on top of a blue LED to fabricate a wLED, and demonstrate its practical feasibility, with a wide color gamut of up to 120% of the NTSC. • A color converter with Pr3+ -doped oxyfluoride glass ceramic was fabricated. • Balanced RGB emission intensities were obtained after heat treatment. • A white LED was composed and showed color gamut up to 120% of NTSC. • The effect of LaF 3 crystal formation on the visible spectra was discussed. [ABSTRACT FROM AUTHOR]

A phosphor-in-glass (PiG) was fabricated to realize a robust white light emitting diode (wLED) with wide color gamut. β-SiAlON:Eu2+ and CaAlSiN 3 :Eu2+ were employed for the green and red phosphors, respectively. Nd 2 O 3 doped silicate glass was used to reduce the emission bandwidths of the phosphors, utilizing the hypersensitive transition of Nd3+: 4I 9/2 → 4G 5/2 , 2G 7/2. The content of green and red phosphors was varied to produce a white emission. The emission spectra, color coordinates and color gamuts of the wLEDs with the PiGs were examined by varying phosphors and Nd 2 O 3 content. A wLED with 5 mol% Nd 2 O 3 doped glass had an enhanced color gamut up to 88%. The thermal stability of the PiGs was also monitored to demonstrate its practical feasibility as a white light source in display applications. • A white LED was realized with a PiG using β-SiAlON:Eu2+ and CASN:Eu2+. • The color gamut has been enhanced up to 88% by introducing Nd-doped silicate glass. • The PiG showed high thermal stability and its practical feasibility. [ABSTRACT FROM AUTHOR]

An oxyfluoride glass-ceramic containing Eu2+-doped nepheline and LaF 3 crystals was synthesized with varying compositions to modify its color conversion and quantum efficiency under ultra-violet light emitting diode (UV-LED) excitation. Glass composing elements such as SiO 2 , Na 2 O and Al 2 O 3 were exchanged with LaF 3 to influence the formation of nepheline crystals within the glass matrix. Among the various combinations, when Al 2 O 3 was replaced by LaF 3 there was improvement in the observed emission intensity and photo-luminescence quantum yield (PL-QY). The optimum composition of Al 2 O 3 and LaF 3 content was investigated to improve PL-QY. X-ray diffractometer (XRD) was used to monitor structural changes in the crystals within the glass-ceramic. A white LED, with a high color rendering index (CRI) comparable to commercial white LEDs, was successfully demonstrated using the modified glass-ceramic as a color converter in structures of phosphor in silicone and phosphor in glass. • Oxyfluoride glass ceramic containing Eu2+-doped nepheline was fabricated. • PL-QY was improved by the modification of glass ceramic composition. • Phosphor in glass and phosphor in silicone were composed with the glass ceramic. • White LED with high CRI up to 85 was successfully achieved. [ABSTRACT FROM AUTHOR]

Abstract: A full-color-emitting phosphor, CaYAl3O7:Pr3+,Ce3+ was synthesized through conventional solid-state reaction. The structural properties of the phosphor were analyzed by Rietveld refinement, maximum entropy method, and luminescent properties were analyzed by co-activating with different rare earth ions. Photoluminescence spectra on excitation with 450nm source were dominated by green band at 490nm originating from 3P0→3H4 transition of Pr3+ ions and less intense band at 617nm due to 1D2→3H4 transition. On codoping with Ce3+, phosphor exhibits an additional broad band originating from 5d1→4f1 (2F7/2 and 2F5/2) of Ce3+, centered at around 540nm due to efficient energy transfer from Pr3+ levels to Ce3+ levels. With this emission property we recommend CaYAl3O7:Pr3+,Ce3+ as potential single-phase full-color-emitting phosphor for solid-state lighting applications. [Copyright &y& Elsevier]

Phosphor in glasses (PiGs) were fabricated for color tunable white LEDs using glass of the SiO 2 -B 2 O 3 -ZnO-Na 2 O system, which can be sintered at 550 °C. CaAlSiN 3 :Eu 2 + (CASN:Eu 2 + ) red phosphor was added without its thermal degradation, and a mixture with Y 3 Al 5 O 12 :Ce 3 + (YAG:Ce 3 + ) yellow phosphor demonstrated color tunable white LEDs when mounted on a blue LED. Variation of the glass to phosphor and phosphor to phosphor mixing ratio achieved a highly improved color rendering index (CRI), of up to 93. Thermal quenching property was also improved, reaching 98% of its original intensity even at 200 °C; the value depended on the phosphor content. Thermal conductivity values elucidate the improvement. [ABSTRACT FROM AUTHOR]

SiO 2 –Na 2 O–Al 2 O 3 –LaF 3 glasses doped with Eu 2+ and Eu 3+ were synthesized to realize an inorganic color converter for white LED using 400 nm UV LED. Among various rare earth ions, Eu 2+ and Eu 3+ showed prominent emission under 400 nm LED excitation. Carbon and EuF 3 content were varied to control the ratio of Eu 2+ and Eu 3+ during the melting process. When the ratio of Eu 2+ and Eu 3+ within the glass matrix was properly controlled, color coordinates of the photoluminescence spectra could be adjusted to make white colors under 400 nm LED excitation. The emission intensity was increased with subsequent heat treatment which led to the formation of LaF 3 nano-crystals. However, almost no conversion was observed when the glasses were actually mounted on UV-LED to make a white LED. Heavy crystallization of the oxyfluoride glasses was thus investigated to improve its scattering of the light source and color conversion efficiency, and its practical feasibility as an inorganic UV-LED color converter was demonstrated. [ABSTRACT FROM AUTHOR]

Phosphor-in-glasses (PiGs) with rare earth (RE) doped SiO 2 –B 2 O 3 –RO glasses were prepared by embedding YAG:Ce 3+ as the yellow phosphor. Eu 3+ and Pr 3+ were used to dope the glass, varying their concentrations in order to provide red emissions for possible chromaticity-control of white-light emitting diodes (WLEDs). The glass-to-phosphor mixing ratio was also varied to find the proper combination for color-controlled white LEDs. PiGs with RE-doped glasses were sintered at 750 °C and polished to 250 μm in thickness for blue LED color conversion. The photoluminescence spectra of the PiGs were monitored after they were mounted on commercial blue LED chips. Variation of color coordination, color rendering index and correlated color temperature were observed due to red emissions from the doped RE-ions. The spectral contribution of Eu 3+ and Pr 3+ ions to white LEDs under 450 nm LED excitation was discussed. The spatial distribution of phosphors within the glass matrix, and their possible interaction, was inspected by SEM. The thermal quenching effect was also investigated. [ABSTRACT FROM AUTHOR]

Abstract: Rare earth doped oxyfluoride glass ceramics with LaF3 nano-crystals formed inside were fabricated for color converter of UV-LED. Among various rare earth ions, Dy3+ and Eu3+ showed practically utilizable visible emissions under UV-LED excitation of 365nm. The visible emission has been improved by the formation of LaF3 brought by heat treatment. X-ray diffraction and transmission electron microscopy along with its energy dispersive spectra confirmed the formation of LaF3 nano-crystals. Compositional dependence and the effects of heat treatment conditions on the visible emissions have been investigated. The CIE chromaticity coordinates of the glasses were also examined for Dy3+ singly doped and co-doped samples. The effect of LaF3 nano-crystals and co-dopants on the visible emission properties of Dy3+ was discussed. [Copyright &y& Elsevier]