Phosphor-in-glass Research Articles

Color Tunable Emission of Y3Al5O12:Ce3+ and Sm3+‐Doped Zinc–Germanate–Tellurite Glass Nanocomposite Powders and Coatings for Light‐Emitting Diodes Applications

A series of nanocomposite (NC) powders and coatings of ZnO–GeO2–TeO2:xSm3+ glass and Y3Al5O12:Ce3+ nanoparticles (YAG:Ce) are fabricated. Samarium ions concentration of the glass phosphor is varied with x values of 0.3, 1.0, 3.0, and 5.0 mol%. The powder batches are prepared with a 95/5 mass ratio of glass/YAG:Ce and uniaxially pressed to obtain powder pellets that are heat‐treated at 350 °C. Morphology and structural characterization are conducted through X‐ray diffraction analysis, scanning electron microscopy, and Raman spectroscopy. The photoluminescence properties of NCs are investigated under different wavelengths of 340, 403, and 460 nm, showing a global emission tonality in the reddish‐orange and yellowish‐green region according to the estimated CIE 1931 chromaticity coordinates. Also, NC coatings soda–lime glass slides are fabricated, and their photoluminescence is characterized using an UV light‐emitting chip (≈365 nm) and a blue light‐emitting chip (≈460 nm). The global emission under UV and blue light from the light‐emitting diode (LED) chips of the NC coatings shows a color tunability in the warm white light and yellowish‐green region.

Neutron detection via thermoluminescence of Ce3+-doped CaO–Al2O3–B2O3 glass

ABSTRACT For neutron detection applications, we have synthesised glass phosphor materials of Ce3+-doped CaO–Al2O3–B2O3 with consisting boron in two different forms of isotopes, enriched 10B and 11B, called 10B-glass and 11B-glass, respectively. For radiation detections, thermoluminescence (TL) properties of the glasses were investigated with X-ray, proton, and neutron irradiations. The TL properties of X-ray- and proton-irradiated 10B- and 11B-glasses were similar while the TL intensity of neutron-irradiated 10B-glass was much greater than that of 11B-glass. The TL of the 10B-glass was observed across the neutron fluence range of 107–1012 neutrons/cm2, and the intensity increased monotonically with neutron fluence.

Oxidation suppression of Cu in alkaline aluminophosphate glass and the effects for radiation-induced luminescence characteristics

A glass phosphor is an attractive material for applications in radiation detections because of its high workability and availability with a wide range of chemical compositions. Recently, X-ray-induced luminescence of glasses containing various luminescent activators are actively investigated worldwide. In applications as phosphor, tailoring valence state of activators, which can take multiple valence states in glass, is very important. In this research, we studied effects of glass melting atmosphere on the valence state of copper-activator ion in alkaline aluminophosphate glasses and the radiation-induced luminescence characteristics. Optical absorption and X-ray absorption near edge structure spectra of Cu-doped glasses showed that the glass fused in Ar atmosphere contains higher concentration of Cu+ than those prepared in air. In addition, the presence of Cu+ enhances the photoluminescence (PL) quantum yield and PL kinetic constant. Furthermore, the increase of Cu+ concentration resulted an improvement of the X-ray-induced scintillation and thermally-stimulated luminescence intensity.

Luminescence properties of PrF3-doped Sb2O3–ZnO–GeO2 glass phosphors for near-infrared wideband light-source

We synthesized PrF3-doped glass phosphors using a melt-quenching method and investigated the luminescence characteristic aiming at a new near-infrared wideband light-source. Optical activation of Pr3+ ions in the samples was confirmed by absorption spectra measurements. Broad PL spectra from 700 to 1100 nm with four PL peaks 730, 870, 930, and 1040 nm were observed by blue LED excitation in all samples. The observed PL peaks were attributed to 3P0 → 3F4, 1D2 → 3F2, 3P0 → 1G4, and 1D2 → 3F4 transitions of Pr3+ ions. With the increase in the PrF3 concentration, the integrated PL intensity around 1040 nm (1D2 → 3F4) was sharply decreased compared to the other PL peaks. We investigated the contribution of self-absorption and cross-relaxation phenomena to the spectral change by measuring glass thickness dependence of the PL spectra and measuring the PrF3 concentration dependence of the fluorescence lifetimes. The fluorescence lifetime of the PL peak at 1040 nm decreased with increasing PrF3 concentration owing to a non-radiative relaxation pathway stemming from the cross-relaxation phenomena. We found that the cross-relaxation phenomenon is a dominant factor in the luminescence properties of PrF3-doped glass phosphors.

New insights into phosphorescence properties of LuAGG: Long afterglow phosphor-in-glass for optical data storage

Newly long afterglow phosphor-in-glass (PiG) plays pivotal roles in the region of optical data storage. By using solid-phase reactions and unique spectrum modulation methods, a color-tunable PiG with decent persistent phosphorescence which can be tuned from green to blue has been fabricated. Lu3Al2Ga3O12: Ce3+, Cr3+ (LuAGG: Ce3+, Cr3+) based on TBZNA glass could emit bright green light signal located at 350 and 420 nm ascribed to the 5d1/5d2-4f transitions when corresponding optical data was being loadout. The doping of Cr3+ increases the density of the trap and provides additional traps between the shallow trap and the deep trap to capture more electrons, further improving afterglow decay time. And the storage time and cyclic reading times are derived by the method of thermal stimulation. Thereinto, tunable emission color has been obtained via changing the concentration of Ga3+, using UV excitation. Moreover, the influence of the Cr3+/Ga3+ on luminescence properties of long-afterglow-PiG materials have been described in detail. Achieved results confirm that it makes LuAGG-PiG as a long afterglow PiG matrix, demonstrating its promising application in optical data storage.

Up‐conversion phosphor plate for white lighting device using NIR excitation source

AbstractUpconversion phosphors have numerous advantages compared to down conversion phosphor materials, such as a weak background interface, low excitation energy, sharp emission lines, and long lifetimes. Conventionally, blue laser diodes are used to obtain strong white light by combining green‐ and red‐emitting phosphors. The blue‐excited white‐light‐emitting devices can be harmful when the blue light penetrates directly into the human body. However, lower energy excited lighting devices does not harm the human body because of their low‐energy photons are compatible with the biologically safe window. Hence, we present a prototype device that converts invisible near‐infrared light into visible white light. For this, we synthesized orange‐emitting Y2O3:Er3+, Yb3+ and blue‐emitting Y2O3:Tm3+, Yb3+ upconversion phosphors using a solid‐state reaction. Using these, phosphor‐in‐glass (PiG) samples with sintered glass frit were prepared to investigate their optical behavior under low‐excitation energy. The emission color from the stacked PiGs depends on the color balance between the activator ions of Er3+, Tm3+, and Yb3+, and their balance is optimized to obtain a white light. The results might pave the way for designing safe white‐light‐emitting devices using a low‐energy excitation source.

High color rendering index of 94 in white LEDs employing novel CaAlSiN3: Eu2+ and Lu3Al5O12: Ce3+ co-doped phosphor-in-glass.

High color rendering index (CRI) and wide correlated color temperatures (CCTs) white LEDs (WLEDs) employing CaAlSiN3: Eu2+ and Lu3Al5O12: Ce3+ co-doped phosphor-in-glass (PiG) are demonstrated. Through fabrication using a low sintering temperature of 620°C to minimize inter-diffusion between the red phosphor and glass, and adjusting thickness of 0.5-0.7 mm to obtain the chromaticity tailorable co-doped PiG, the WLEDs exhibit high CRI of 94 and wide CCTs of 3900 K to 5300 K. This CRI is the highest yet reported for the co-doped PiG. The proposed of the co-doped PiG with good thermal stability fabricated by using a low sintering temperature may provide a novel technique to achieve high-performance WLEDs with high CRI for use in many high-quality of indoor lighting applications, especially in color inspection, clinical inspection, and gallery lighting.

Heat Dissipation Enhancement of Phosphor-Converted White Laser Diodes by Thermally Self-Managing Phosphor-in-Glass

Laser-driven white lighting has been considered as a next-generation high-brightness white lighting source. Thermally stable color converter is an essential down-conversion material for phosphor-converted white laser diodes (pc-wLDs), which inevitably endures high-density laser excitation and huge heat shock from conversion loss. In this work, we proposed a thermally self-managing phosphor-in-glass (PiG) converter to enhance the heat dissipation of reflective pc-wLDs. The PiG converter was prepared by printing and sintering a phosphor glass film on the cold side of thermoelectric cooler (TEC). By controlling the input current of TEC, the heat generated from phosphors under high-power laser excitation was effectively and initiatively dissipated into the ambient environment due to the Peltier effect of TE materials. As the laser power (LP) increases from 0.73 to 5.6 W, the working temperature of PiG film slowly increases from 2.3°C to 6.1°C. The maximum temperature of PiG film is reduced by 61.1 °(~91%) at the LP of 5.6 W. Furthermore, the PiG-TEC-based pc-wLD achieves a cool white light and stable light quality under various LPs. At the LP of 4.5 W, the correlated color temperature (CCT) of pc-wLD is 6449 K, and the chromaticity coordinate of pc-wLD is (0.3139, 0.3274). The results indicate that the proposed PiG-TEC converter enhances the thermal performance of high-brightness laser-driven white lighting.

Phosphor in glass using β-SiAlON:Eu2+, CaAlSiN3:Eu2+ and Nd-doped silicate glass for enhanced color gamut of white LED

A phosphor-in-glass (PiG) was fabricated to realize a robust white light emitting diode (wLED) with wide color gamut. β-SiAlON:Eu2+ and CaAlSiN3:Eu2+ were employed for the green and red phosphors, respectively. Nd2O3 doped silicate glass was used to reduce the emission bandwidths of the phosphors, utilizing the hypersensitive transition of Nd3+: 4I9/2 → 4G5/2, 2G7/2. 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 Nd2O3 content. A wLED with 5 mol% Nd2O3 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.

Fabrication of red-emitting CaAlSiN3: Eu2+ through phosphor-in-glass approach for application in rear combination lamp

In this study, the red-emitting phosphor-in-glass (PiG) using the CaAlSiN3: Eu2+ (CASN) phosphor is reported for the first time. The CASN: Eu2+ PiG samples with a maximum luminous flux of 25.1–29.4 for l minute at laser power of 1 W/mm2 was obtained using a low-temperature glass frit and GPS furnace. Despite the increase in the phosphor from 15 to 25 wt%, the PiG produced at low temperature of 380 °C showed robust properties. Finally, the red PiG module designed for rear lamp applications maintains over 90% lumens for a minute at 350 mA and achieves an intense red light having a color temperature of 4589 K.

Fabrication of stacked color converter for high-power WLEDs with ultra-high color rendering

White light-emitting diodes (WLEDs) with high color rendering is strong required in some color-critical lighting applications. However, developing a stable color converter with broad emission remains an outstanding challenge for high-power WLEDs. Herein, a stacked color converter of red CaAlSiN3:Eu2+ (CASN) phosphor-in-silicone (PiS) layer coated on a green Y3Al3.08Ga1.92O12:Ce3+ (YAGG) phosphor-in-glass (PiG) was fabricated to realize ultra-high color rendering for high-power WLEDs. The YAGG PiG was prepared by printing and sintering the mixture of YAGG phosphor and borosilicate glass matrix, and then the CASN PiS layer was coated the YAGG PiG. The PiS thickness was controlled to adjust the luminescence of converters. The converter exhibits a broad emission due to the compensation of cyan valley. The converter enables a pure white light with an ultra-high color rendering (Ra = 96.1, R9 = 90.1, R13 = 98.5; Rf = 92, Rg = 100) and chromaticity coordinates (0.367, 0.372). The WLED achieves stable color quality under various driving currents.

Reflective Phosphor-in-Glass Color Converter for Laser-Driven White Lighting

In this work, we fabricated a phosphor-in-glass (PiG) film on Al-coated sapphire as reflective color converter driven by a laser diode. The borosilicate glass PiG film was sintered on heat-conducting sapphire and an Al thin layer with high reflectivity was deposited on the other surface of the sapphire, providing the function of heat dissipation and light reflection. The optical performance of the laser-driven white emitter (LD-WE) was adjusted by controlling the PiG film thickness. At a thickness of $120~\mu \text{m}$ , the LD-WE emits white light with a correlated color temperature (CCT) of 6733 K and a chromaticity coordinate of (0.3104, 0.3184). When the laser power increases from 0.32 to 1.12 W, the luminous flux increases from 19.3 to 129 lm and the light quality is stable. The color rendering index (CRI) of LD-WE reaches 82.5 by adding red phosphor. Furthermore, the converter has low working temperature from 30.7 to 45.6°C due to the effective heat transfer of sapphire.

White emitting aluminosilicate glass phosphors derived from Dy3+, Ag+ co-exchanged LTA zeolite

White emitting glass phosphors were derived from the Dy3+, Ag+ co-exchanged LTA zeolite by heat treatment. Attributed to the porous structure and low Si:Al ratio of LTA, an aluminosilicate glass phosphor with outstanding thermomechanical and optical properties was obtained at a relatively low melting temperature. Due to the energy transfer from the Ag+ ions to the Dy3+ ions, the emission intensity of the Dy3+, Ag+ co-doped sample (λex = 250 nm) was improved by 4 times compared with the Dy3+ singly doped sample (λex = 388 nm). And the chromaticity coordinates moved from the yellow region to the white region. All the results suggested a facile method to fabricate glass phosphors for white light source applications.

Design and Evaluation of Automotive Laser Headlight Based on the Scanned Beam on Phosphor-in-Glass Plate

We designed and evaluated an optical system of automotive laser headlight with the application of phosphor-in-glass (PiG) plate as a wavelength converter and the scanned laser beam using Microelectromechanical system (MEMS) scanner to improve the optical and thermal performance of the PiG plate. By applying laser scanning, it was improved on both deviations of correlated color temperature (CCT) and intensity in white light emitted through the PiG plate. A TiO₂ film was also applied under the PiG plate to further improve the CCT and intensity deviation by additional scattering effect. In addition, it was confirmed that there is little temperature deviation on the PiG plate of 0.2℃ with the scanned laser beam, resulting in the reduced damage on the PiG plate. By experimental evaluation, we have confirmed that PiG plate can be used as a good wavelength converter with an aid of laser scanning for various laser application fields including automotive laser headlight.

Nitridated Ca2NaMg2V3O12: Eu3+ Vanadate Garnet Phosphor-in-Glass.

In this study, Ca2NaMg2V3O12 coordination compound undoped and doped with Eu3+ obtained in the air and ammonia atmosphere by solid-state reaction was investigated. Ca2NaMg2V3O12: Eu3+ obtained in the ammonia atmosphere was then investigated as a phosphor-in-glass (PiG). Annealed Ca2NaMg2V3O12: Eu3+ phosphor forms a single phase with the cubic garnet structure and Ia3d space group. Nitridation in ammonia causes a widening of a VO43− group emission band on the low energy side and it red-shifts by 20 nm. The emission of Eu3+ is extended as compared to the non-nitridated phosphor. Ca2NaMg2V3O12: Eu3+ after nitridation shows higher emission quantum yield (QY): 49 vs. 45 and lower correlated color temperature (CCT) and 4179 vs. 4998 as compared to phosphor without nitridation. The QY for PiG is 55. The thermal stability of nitridated phosphors is superior to phosphor obtained in the air atmosphere and is further enhanced for PiG.

Photon quantification in Ho3+/Yb3+ co-doped opto-thermal sensitive fluotellurite glass phosphor.

Multi-photon-excited thermal-correlated green and red upconversion (UC) emissions have been quantified in Ho3+/Yb3+ co-doped fluotellurite (BZLFT) glass phosphor under the 978 nm laser excitation. The temperature dependence of the fluorescence intensity ratio (FIR) originated from UC emissions bands centered at 550 nm and 661 nm has been verified in the range of 303-543 K. The net emission photon numbers of 5F4+5S2→5I8 and 5F5→5I8 transition emissions are up to 40.08×1012 and 68.51×1012cps in the 0.4wt.%Ho2O3-0.4wt.%Yb2O3 co-doped BZLFT case under the 6.95W/mm2 laser power density. Furthermore, the quantum yield (QY) and luminous flux are determined to be dependent on pumping power. When the excitation power increases 874 mW, the QY values for 550 nm and 661 nm emissions are as high as 0.94×10-5 and 1.60×10-5. In addition, the high photon producing efficiency is conducive to ensuring high feedback to thermosensitive performance. The temperature thermal sensor can be manipulated steadily in medium temperature range, and the relative sensitivity reaches 0.4%K-1 at 303 K, which is 1 order of magnitude larger than those in several rare-earth-doped materials. Efficient photon conversion ability and high temperature sensitivity indicate that the rare-earth-ion-doped fluotellurite material has a prospective application in the construction of optical temperature sensors based on the FIR technique allowing for self-referenced temperature determination.

Adhesive resin composites with ceramic nanoparticles for enhanced light extraction efficiency of sandwiched LED device structure

While phosphor-in-glass (PiG) technology is widely used in white light-emitting diodes (WLEDs), the adhesive layer between the PiG plate and the blue LED chip does not match their refractive indices, resulting in a reduction in efficiency. To address this issue, we applied ZrO2 nanoparticles with an average particle size of 10 nm to the adhesive layer as refractive index enhancer and light scattering additives in the form of polymer matrix nanocomposites. An adhesive layer with proper ZrO2 nanoparticles can enhance the luminous flux and efficacy of the WLED by refractive index matching, light scattering and increased view angle. The optimum ZrO2 content in the adhesive layer was identified as 9 wt.% and in this case, the viewing angle was extended by 8% and luminous efficacy was improved by about 3.1 % while maintaining uniform CCT and color bin. The methodology for improving the efficiency of LEDs demonstrated in this paper is expected to be of great help to the development of high-performance WLEDs.

Recycled Glass and Ce‐Doped‐Y3Al5O12 Nanoparticles Phosphor‐in‐Glass for White Light‐Emitting Diodes Applications

A series of nanocomposites of recycled soda‐lime glass from a glass container and Y3Al5O12:Ce3+ (YAG:Ce) phosphor nanoparticles are fabricated by the two‐step low‐temperature co‐sintering technology. A transparent glass bottle from a commercial beverage is used as glass frit source and mixed with YAG:Ce nanoparticles. Afterward, the powders are pressed to obtain pellets with phosphor concentrations in the range of 2.5–15 wt%. The pellets are sintered at 800 and 900 °C. X‐ray diffraction (XRD) analysis shows that YAG:Ce nanoparticles are conserved even after sintering at 900 °C. The XRD analysis shows that YAG:Ce nanoparticles are conserved even after sintering at 900 °C. The emission spectra of the Ce3+ ions of yttrium aluminum garnet (YAG) nanoparticles combined with the transmitted blue light exhibit color tuning related to the phosphor concentration and the sintering temperature. A tonality shift from cold‐white light toward yellowish‐green region is observed according to the estimated CIE 1931 chromaticity. Thus, recycled glass from a commercial glass container and YAG:Ce nanoparticles phosphor‐in‐glass (PiG) can be an eco‐friendly and low‐cost alternative as color converters.

Mapping the glass forming region and making their phosphor‐in‐glass for application in W‐LEDs packaging

AbstractThe application of phosphor‐in‐glass (PiG) packaging material in white‐light emitting diodes (W‐LEDs) can improve the thermal stability and luminous efficacy of LED devices. In this work, a low melting point glass of TeO2–ZnO–Na2O–B2O3 (TZNB) was selected as glass matrix, and mixed with YAG: Ce3+ phosphor powders to obtain phosphor‐in‐tellurite glass (PiTG). In a significant advance, we mapped the glass forming region of TZNB for the first time. This high refractive index glass matrix with low melting temperature was achieved by optimizing the glass composition. The refractive index increased regularly from 1.61 to 2.03, when the dosage of TeO2 increased from 15 to 75 mol%. Through Monte Carlo simulations and numerical calculations, the optimal structure of gradient refractive index (GRIN) was designed, which is consisted of TZNB‐1 (n = 2.03), TZNB‐4 (n = 1.79), TZNB‐6 (n = 1.66), and glass substrate (n = 1.52). The PiTG with GRIN coating was fabricated by screen printing and low‐temperature sintering, and the optimized sintering temperature is 575°C. Compared with the single refractive index (SRIN) coating, the luminous efficacy of PiTG with GRIN coating was enhanced from 9.51% to 23.12%. Therefore, this work provides a significant application in high‐power W‐LEDs.

Phosphor-in-glass (PiG) plates for blue laser diode driven white-light emission

Abstract Owing to the great thermal stability, phosphor-in-glass (PiG) is a promising color converter for the laser diode (LD) excitation based high-power white light-emitting LDs. Here, we reported the rapidly developed PiG plates using a facile microwave irradiation technique where the YAG:Ce3+ phosphor embedded with soda-lime silica glass. The effects of phosphor content and microwave irradiation energy were studied for investigating the optimal performance of PiG plate. To evaluate the practical applicability, the luminescence and thermal properties of the PiG plate was compared with the commercial YAG:Ce3+ single-crystal. The PiG plate and YAG:Ce3+ single-crystal individually combined with blue LD exhibited the white light with the CIE color coordinates of (0.3016, 0.3098) and (0.3254, 0.3555), respectively. The maximum surface temperature of the PiG plate was found to be about 96.1 °C, which is much lower than the YAG:Ce3+ single-crystal of 124 °C. The change in the CIE color coordinate of the PiG with aging time is smaller than that of YAG:Ce3+ single-crystal. This PiG plate might provide an important implication to overcome current limitation of LD driven solid state laser lighting.