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The formation mechanism of Cd–S–Se quantum dots (QDs) with a CdS/CdSe core–shell structure within a silicate glass system was investigated by monitoring the change in the first excitonic absorption peak of CdSe, CdS, and Cd–S–Se QDs as a function of the heat‐treatment (HT) duration. When a silicate glass containing QD formation components for CdSe or CdS single‐phased QDs was heat‐treated, CdSe QDs grew via Ostwald ripening, whereas CdS QDs hardly formed within the given silicate glass matrix. When the glass, including CdO, ZnSe, and ZnS, was utilized for the synthesis of Cd–S–Se QDs within the glass matrix, Cd–S–Se QDs were successfully formed and exhibited similar growth behavior to CdSe QDs during the initial stage of HT. The structural changes in the QD‐embedded glasses during HT were also monitored by Raman spectroscopy and discussed, and a possible formation mechanism of CdSe/CdS core–shell‐structured QDs within silicate glasses is suggested. [ABSTRACT FROM AUTHOR]

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]

Spectroscopic properties and room-temperature persistent spectral hole burning mechanisms of Eu[sup 3+] -doped borate glasses were investigated. The depth of the burnt hole increased K. The photoreduction of Eu[sup 3+] to Eu[sup 2+] is a primary mechanism of hole burning and this hypothesis was supported by spectral hole properties, relaxation properties as well as changes in the local structure of Eu[sup 3+] in glasses. [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]

Nd3+-doped silicate glass (Nd-glass) was employed as a color filter for a white LED based on red and green phosphor (RG-LED), to manipulate the photoluminescence spectral shape and thus to provide a wider color gamut. The hypersensitive transition of Nd3+:4I9/2→4G5/2,2G7/2 was adjusted via glass composition and Nd concentration, and improved absorbance as well as reduced the absorption bandwidth. The effective absorption of the Nd-glass at ~580 nm reduced the spectral linewidth of the green and red emissions, improving the color reproduction range. The color gamut of the RG-LED was improved from 75.3% to 81.6% NTSC by the introduction of Nd-glass as a color filter. Reliability under high operating current and high temperature were also examined and 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]

Silicate glasses with CdS and CdSe quantum dots ( QDs) were synthesized for application as an inorganic color converter for a 450-nm blue light-emitting diode ( LED). CdO and ZnS (or ZnSe) were added, and heat treatment conditions were changed to control QD formation within the silicate matrix. Absorption spectra and high-resolution transmission electron microscopy confirmed the QD formation. Variations in absorption and photoluminescence ( PL) spectra were observed with CdSe QD-embedded glasses when heat treatment conditions varied, whereas glasses with CdS QDs did not show noticeable variation. QD-embedded glasses were then mounted on top of a 450-nm LED chip to make a color-converted LED, and their electroluminescence and PL spectra as well as CIE color coordinates were investigated. The practical potential of QD-embedded glasses as an inorganic color converter has been observed, and their spectral properties were discussed. [ABSTRACT FROM AUTHOR]

Silicate glasses containing CdS and Ag2O were made by the melt-quenching method. CdS quantum dots ( QDs) were precipitated inside the glass matrix by heat treatment at 570-590 °C for 10 h, and the influence of Ag on photoluminescence ( PL) of CdS QDs was investigated. The emission located at 478-493 nm in wavelength originated from the direct recombination of electron/hole pairs was quenched due to charger transfer between Ag and CdS QDs. Modification of PL from CdS QDs by Ag provides potentials toward developing the color changing materials for light-emitting diodes ( LEDs). [ABSTRACT FROM AUTHOR]

Abstract: Glasses with a P2O5–SnO–MnO ternary system were synthesized and characterized. Glass forming range was determined to be 5–20mol% of MnO when the content of SnO was kept below 50mol%. Various analyses including thermal, optical and structural characterization were performed on (85− x)P2O5–xSnO–15MnO (x =30, 35, 40 and 45 in mol%) and (55− y)P2O5–45SnO–yMnO (y =0, 5, 10 and 15 in mol%) glasses in order to investigate the compositional effect of SnO and MnO on the properties of glass. Glass transition temperature of all the prepared glass samples turned out to be below 350°C, but showed a compositional dependency on SnO and MnO, which was discussed in terms of the structural changes derived from Raman spectroscopy. The visible transparency of both glass series was identified with their high optical bandgap of 3.4–3.7eV and their refractive indices varied between 1.6 and 1.9 depending on the wavelength monitored and composition. Er3+ doped the glasses to examine their potential as a photonic gain medium. Radiative emission properties, Judd–Ofelt analysis and stimulated emission cross-sections also exhibited the influence of SnO and MnO and suggested the preferred concentrations of SnO and MnO as 35mol% and 5mol%, respectively. Modification of the local structure around the Er3+-ion upon the compositional variation was responsible for the phenomena. This is also discussed with the structural contribution of SnO and MnO. [ABSTRACT FROM AUTHOR]

Addition of CsBr and KBr into Eu3+-doped Ge–Ga–S glasses resulted in persistent spectral hole burning with high quantum efficiency, whereas the addition of alkali chloride did not show any evidence for a hole formation process. The characterization of the phonon side band spectra revealed the site for Eu3+ ions located near the Ga–Br− or Ga–Cl− units. The presence of Br− ions near Eu3+ lowers the energy of the conduction band, thereby enabling the interaction between the 4f electrons and the resultant conduction band. The interaction made the photo-reduction of Eu3+ to Eu2+ possible. However, the higher coupling of phonon energy with Eu3+ together with the higher electronegativity of Cl− ion in CsCl-containing glass compared to its CsBr counterpart, hindered the photo-reduction of Eu3+ into Eu2+. [Copyright &y& Elsevier]

Fluorescence and efficient persistent spectral hole burning of Eu3+ at 77 K were observed in chalcohalide glasses. The depth of the hole was approximately 30% after a burning process of 1 min with 50 mW power, and it was completely erased with Ar+ laser irradiation. The hole survived room temperature heat treatment and showed good thermal stability. The hole-burning mechanism was most probably the photo-reduction of Eu3+→Eu2+. Fluorescence from Eu3+ decreased with increasing temperature and disappeared at the temperature above ∼130 K. [Copyright &y& Elsevier]

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]

High-refractive index glasses are used to produce glass lenses by the precision optical Glass Mold Press (GMP) process and have been extensively studied because of increased demand for their application in telecommunications, optical lenses, and cameras. Borate glasses containing Ta 2 O 5 , Nb 2 O 5 , La 2 O 3 and Gd 2 O 3 have mainly been used as materials for GMP because of their excellent optical properties and low production cost. This study conducted a systematic investigation of the B 2 O 3 –La 2 O 3 –Ta 2 O 5 –SiO 2 quaternary glass system for precision GMP applications. The glass forming range of the quaternary system was studied using (B 2 O 3 +SiO 2)–La 2 O 3 –Ta 2 O 5 and changes in physical and thermal properties such as refractive index, density and glass transition temperature of the obtained glasses were examined. Compositional dependent structural changes were also inspected by Raman spectroscopy and solid state nuclear magnetic resonance (NMR) analyses, to determine the compositions' effect on thermal and optical properties. [ABSTRACT FROM AUTHOR]

Irradiation of x-rays has induced room-temperature persistent spectral hole burning (PSHB) in Eu[sup 3+]-doped borate glasses melted under an inert atmosphere. Defects were formed by x-ray irradiation and these defects, especially electron trapping centers near rare-earth ions in glasses, were responsible for the PSHB. Electrons were released from these defects upon irradiation of a burning light. Photoreduction of Eu[sup 3+] to Eu[sup 2+] by trapping these electrons resulted in the formation of persistent spectral holes. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Thulium (Tm3+)-doped boro-tellurite glasses were prepared by melt-quenching technique and their optical, photo-luminescence (PL), and time-resolved spectroscopic behaviors were studied. The Judd-Ofelt (J-O) parameters were calculated from the absorption spectra and evaluated the radiative factors for emission transitions. The PL and up-conversion (UC) emission spectra were measured under the excitation wavelengths of 473, and 793 nm diode lasers, respectively. The emission peak of 3H 4 →3H 6 (793 nm) and up-conversion 3F 2,3 → 3H 6 (696 nm) transitions shifted to higher wavelengths with the increment of Tm 2 O 3 concentration, while the 1G 4 →3F 4 (650 nm), 3H 4 →3F 4 (1466 nm) and 3F 4 →3H 6 (1821 nm) transitions showed no change in peak positions, under 473 nm laser excitation. The time-resolved spectroscopic measurements are recorded and analysed for all transitions. Under 793 nm laser, NIR emission spectra (1200–2200 nm) and spectroscopic characteristics were measured to discuss the energy transfer mechanisms. The strong transitions of 3H 4 →3F 6 (1466 nm) and 3F 4 →3H 6 (1821 nm) were observed and corresponding emission cross-section and gain factors have been evaluated and discussed for the application of the S-band communication window. • Tm3+ concentration-dependent borotellurite glasses were synthesized. • Structural and optical characteristics were studied and discussed. • Judd-Ofelt intensity parameters were evaluated and compared. • Photoluminescence and upconversion emission features were investigated. • The present glass showed high NIR emission cross-section at 1.8 μm. [ABSTRACT FROM AUTHOR]

Various rare earth (RE) oxides such as Pr 2 O 3 , Dy 2 O 3 , Ho 2 O 3 , and Er 2 O 3 were introduced into Cd–S–Se quantum dot embedded glasses (QDEGs) to investigate their effect on the color conversion properties of the Cd–S–Se QDEGs. The absorption and emission peak wavelengths due to the excitonic transition of the Cd–S–Se QDs were modified by the introduction of RE oxides, implying their influence on QD formation. The photoluminescence of the various QDEGs RE oxides under 450 nm excitation were monitored and compared with the un-doped QDEGs. White LEDs (wLEDs) were also fabricated with the RE-doped QDEGs and their color conversion properties, such as quantum yield (QY), luminous efficacy, correlated color temperature (CCT) and color rendering index (CRI) were examined. Transmission electron microscope (TEM) revealed that the size and spatial distribution of the QDs were improved by the RE-oxides. Their effect on QD formation within the silicate glass was discussed using Raman spectroscopy. • Cd–S–Se quantum dot embedded glasses (QDEG) with various rare earth (RE) ions were fabricated. • RE ions reduced QD size and modified spectral properties of QDEGs. • RE ions improved size and spatial distribution of QDs within glass matrix. • White LED was successfully achieved with RE-doped QDEGs. [ABSTRACT FROM AUTHOR]

Silicate glasses based on SiO 2 –B 2 O 3 -BaO-WO 3 (SBBW) are synthesized with varying added Al 2 O 3 content, and their thermal and structural properties are examined as a sealing material for reversible solid oxide fuel cells (RSOCs). When up to 17.5 mol%, Al 2 O 3 is added, glass stability is improved at the expense of viscosity at sealing temperature. The glass transition temperature (T g), coefficient of thermal expansion (CTE) and flow at sealing temperature are investigated while varying Al 2 O 3 content, to find the proper composition for RSOC sealing. The structural changes in the glasses resulting from the Al 2 O 3 are inspected using Raman spectroscopy and an X-ray diffractometer. The adhesion characteristics of the glasses are examined by applying the glasses between NiO-yittria stabilized zirconia (NiO-YSZ) and Crofer22APU. A RSOC stack with 15 cells is prepared with glass containing 10 mol% of Al 2 O 3 as a sealing material, and the practical feasibility of the glass is successfully demonstrated. The open circuit voltage is monitored while cycling the RSOC stack between water electrolysis mode and fuel cell mode. [ABSTRACT FROM AUTHOR]

Abstract: CdSe quantum dots (QDs) were precipitated in silicate glasses under various durations and temperatures of heat-treatment. Absorption and photoluminescence (PL) spectra of the QDs showed the quantum confinement effect from CdSe QDs. When the glass was heat-treated for 10h, estimated average QD sizes increased from 5.2nm when the glass was heat-treated at 490°C and to 6.9nm when it was treated at 500°C. When the glass was heat-treated at 480°C, estimated average QD sizes were 4.9nm after 20h and 5.3nm after 30h. The PL peak position was independent of the excitation wavelengths; this result indicates that the size distribution of CdSe QDs was narrow. [ABSTRACT FROM AUTHOR]

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]

BaF 2 –Al 2 O 3 –B 2 O 3 –SiO 2 glasses and glass-ceramics doped with Eu3+-Tb3+ were fabricated as an inorganic color converter for white LEDs. The BaF 2 –Al 2 O 3 –B 2 O 3 glass composition was modified by adding SiO 2 , and thermal and mechanical stability improved with increasing SiO 2 content while maintaining a quantum yield (QY) as high as 91%. To realize white color coordinates, Tm3+ was additionally introduced at varying contents, and Eu3+ content was also controlled. Excellent chromatic properties, such as a pure white color coordinates (x = 0.33, y = 0.33) with a co-related color temperature of 5772K, and a color rendering index (CRI) of 91 under 370 nm excitation, were successfully achieved. After the glass was heat-treated at 600 °C to fabricate a glass ceramic, the glass-ceramics were mounted on top of a 370 nm UV-LED, successfully demonstrating a white LED with nearly pure white color coordinates and a high CRI of 86. The increased emission intensity in the glass-ceramic was attributed to the formation of BaF 2 crystals which were investigated by X-ray diffractometer (XRD) and a transmission electron microscope with energy dispersive spectroscopy (TEM-EDS). • Glass composition was modified to improve mechanical and thermal properties. • Tm3+ ions were additionally doped for blue emission under UV light. • Tb-Eu-Tm contents were adjusted to make a white color coordinate. • Emission intensity was improved with heat treatment at 600 °C for 10hrs due to form the BaF 2 crystal. • White color coordinate (0.36, 0.36) was successfully achieved with high CRI of 85 under 370 nm UV LED chip. [ABSTRACT FROM AUTHOR]

Abstract: Spectroscopic properties of Pr3+-doped selenide glasses and optical fibers were investigated for their mid-infrared applications in the spectral range of 3.5–5.5μm. Optimal concentration of Pr3+ was decided, and sensitizers for improved spontaneous emission of Pr3+: (3F2, 3H6), 3H5→3H4 transition were examined. Spectral deconvolution analysis with corrected emission bands revealed effective interaction of the excited energy states. Optical fibers doped with Pr3+ were fabricated and their spectroscopic properties were measured. Pumping scheme and energy transfer mechanism of the selenide fiber were investigated and discussed for its practical use. [Copyright &y& Elsevier]

Abstract: Effects of CsI content on the optical properties of Ge30Ga5Sb5Se60 glasses were evaluated. Linear and non-linear absorption properties of the glasses without Pr3+ were examined in addition to 1.6μm emission properties of the Pr-doped glasses. Blueshift of the UV-side absorption edge was accompanied with increasing CsI concentration, while non-linear absorption coefficients measured at 1.06μm by the Z-scan method remained unaffected. Measured lifetimes of the 1.6μm emission from modified glasses were comparable to those of the unmodified glass. These experimental observations are discussed in connection with a pronounced weak absorption tail appeared in selenide glasses with the addition of CsI. [Copyright &y& Elsevier]

SiO 2 –Na 2 O–Al 2 O 3 –LaF 3 glasses doped with Eu2+ and Mn2+ were synthesized to fabricate an inorganic color converter for white LED. When Eu2+ was formed within the glass matrix, the obtained glasses showed cyan emission under 400 nm excitation upon heat treatment and the emission peak has been shifted with the crystallization. White emission has been successfully achieved with the introduction of Mn2+ which supplemented red emission. The glass ceramic has been mounted on a 400 nm UV-LED and successfully demonstrated its practical feasibility with color rendering index of 91.3. The effect of heat treatment and energy transfer between Eu2+ and Mn2+ has been discussed. • Color converters with Eu2+ and Mn2+ doped oxyfluoride glass ceramic is fabricated. • Eu2+ shows cyan emission and its intensity increase with heat treatment. • Red emission due to Mn2+ has been observed with the energy transfer from Eu2+. • White LED has been successfully demonstrated with high color rendering index of 91. [ABSTRACT FROM AUTHOR]