Phosphor-in-glass Research Articles

Efficient thermal and luminescent regulations of LuAG: Ce-PiG based remote LED/LD

The quantum loss in phosphor-in-glass (PiG) and energy loss in LD/LED exciting source could aggravate the thermal load of a glass-based luminescence device. In this study, luminous efficiency of radiation (LER) and thermal shock in LuAG: Ce PiG-based remote LD/LED prototypes were regulated effectively, by controlling the exciting distance between PiG and blue LD/LED. For remote LD, both the simulated temperature and the real working temperature of LuAG: Ce-PiG were initially increased and then declined with increase of the exciting distance (the numerical difference: 9.3%). The maximum working temperature of LuAG: Ce-PiG was 135.1 °C. Remarkably, LER of LuAG: Ce-PiG was initially reduced and then elevated with increase of the exciting distance, and the obtained maximum LER was 203.97 lm/W. Meanwhile, increasing the working distance leads to the decrease of both LER and working temperature of the PiG based LED, since the excitation loss was negatively correlated to the exciting distance. For the better application of LD/LED device in high power lighting and display, this work strictly controlling exciting distance is highly necessary.

Yellow YAG-Ag/Al2O3 film applied to blue laser illumination

The most popular light-emitting component for laser illumination right now is phosphor in glass (PiG), however its major weakness is the poor heat conductivity. In this research, the yellow YAG:Ce phosphor and Ag paste were co-fired on an Al2O3 substrate using the blade-coating approach to create a PiM (phosphor in metal) film. Due to the ultra-high thermal conductivity of Ag, the highest blue laser power density that YAG-Ag PiM can achieve is 9.2 W·mm−2, and the maximal luminous flux, lumen efficiency and CCT (correlated color temperature) are 620 lm, 172 lm·W−1 and 6244 K, respectively.

Triple-layer remote phosphor geometry: an excellent selection to improve the optical properties of white light-emitted diodes

High performance white-light-emitting diodes (WLEDs) have been the goal of recent research on phosphor-in-glass (PiG) devices. In this paper, we introduce a configuration of WLED that achieves high color rendering index (CRI), and correlated color temperature with the addition of Zn<sub>2</sub>SiO<sub>4</sub>:Mn<sup>2+</sup>, As<sup>5+</sup> and YAl<sub>3</sub>O<sub>4</sub>B<sub>12</sub>:Eu<sup>3+</sup><sub>. </sub>The technique is lower the temperature during the creation process of phosphor in glass and control the consistent thickness in between 0.5 to 0.7 mm to yield high color quality PiG, high CRI above 80 WLEDs, and extend the color temperature range to 3,900 to 5,300 K. The consistent heat generation combined with extraordinary CRI for PiG prove that low temperature sintering has the potential to create WLEDs with advanced quality. The improved WLEDs can be utilized in many high-demand lighting fields such as chromatic examination, medical analysis, and aesthetic lighting.

Introducing TiO2 to design high-reflectivity AlN composite substrates to synthesize green/white converters for high-brightness reflective laser illumination☆

Phosphor-in-glass (PiG) has been prepared into various types of phosphor films owing to its simplicity process, exceptional color purity, and convenient color adjustability. Nevertheless, existing reflective PiGs films have encountered limitations in terms of stability and feasibility as reliable color converters, mainly attributed to issues related to thermal deposition and insufficient optical efficiency. Herein, we propose to use AlN substrate with superior thermal conductivity to coat the TiO2 layer to obtain TiO2–AlN (TA), which enhances the reflectivity of blue light to facilitate the light conversion process. By incorporating highly thermally stable LuAG:Ce-PiGs on a TA substrate, the LuAG:Ce-PiTA converter exhibits a luminous flux of 1102 lm@6.4 W, and maintains a relative intensity of 94.6% at 473 K benefiting from the high thermal conductivity of 34.1 W/(m·K). The addition of CASN3:Eu to the color converter 50 L&10C-PiTA enables an impressive CRI of 90.7. Relative luminescence intensities of LuAG:Ce-PiTA and 50 L&10C-PiTA only decrease by 5.35% and 3.28%, respectively, in the 24 h illumination aging decay test of the reflective laser module. The results confirm the suitability of the optimally designed TA substrate for LuAG:Ce color converter applications in high-power reflective laser illumination.

Defect Detection Method of Phosphor in Glass Based on Improved YOLO5 Algorithm

Phosphor in Glass (PiG) is easy to be stirred unevenly during production and processing, and improper use of instruments and other factors lead to defective products. In this paper, we propose an improved YOLOv5 target detection algorithm. Firstly, the Coordinate Attention (CA) is introduced into the backbone network to enable the network to notice detect targets in a larger range. Secondly, the Bidirectional Feature Pyramid Network (BiFPN) is used to fuse different scale information in the neck part to obtain the output feature map with rich semantic information. At the same time, the weighted bidirectional feature fusion pyramid structure adjusts the contribution of different scale input feature maps to the output by introducing weights. This optimization enhances the feature fusion effect, reduces the loss of feature information in the convolution process, and improves detection accuracy. Then, the GIOU_Loss function is replaced with the EIOU_Loss function to speed up the convergence. Finally, the comparative experiment is carried out with the self-made PiG dataset. The experimental results show that the average accuracy mAP of this method is 12.35% higher than that of the original method (YOLOv5s), with a detection speed is 53.92 FPS, aligning with the actual needs of industrial detection.

Highly efficient and thermally robust phosphor-in-glass ceramic (PiGc) for high-brightness laser-driven lighting

How to improve the luminous efficiency (LE) and thermal stability of phosphor conversion materials have always been the focus of high-brightness laser-driven lighting. In this study, we successfully prepared a series of phosphor-in-glass ceramics (PiGc) by conducting a crystallization heat treatment on phosphor-in-glass (PiG) made from LuAG:Ce3+ phosphor and Li2O–Al2O3–SiO2 (LAS) glass via a spark plasma sintering (SPS). Comparing to PiG, the optical and thermal performances of PiGc have been enhanced significantly, including a higher internal quantum effect of 81.2% and lower thermal quenching (it remains 86% at 473k). By precipitating β-spodumene crystals, the coefficient of thermal expansion (CTE) of the PiGc decreased by 15% at 700 °C. Meanwhile, the use of precipitated nanocrystals as 'light-scattering centers' improved luminous efficiency remarkably. Under excitation of 450 nm blue laser with 7.04W/mm2, the LE of the most optimal sample was improved from 209.5 lm/W to 232.2 lm/W. These results indicate that crystallization heat treatment is an effective method for improving the LE and thermal stability of PiG. The PiGc is a highly efficient and thermally robust phosphor conversion materials for high-brightness laser-driven lighting.

Lithium-aluminium-silicate glass: A novel high-quality glass for preparing LuAG: Ce colour converter for laser illumination

Phosphor-in-glass (PiG) plays an indispensable role as a highly tunable and easily prepared phosphor material for new-generation high-brightness and high-collimation laser lighting (blue laser diodes + colour converters). However, at low power (<5 W), the poor thermal stability and brittleness of PiGs make it challenging to develop high-intensity, high-brightness PiG materials because of their susceptibility to rupture and sudden drop in luminous efficiency (LE) owing to thermal accumulation under high-energy laser irradiation. In this study, a performance-tunable lithium-aluminium-silicate (LAS) glass system was used to adjust the glass composition and synthesise LAS-glasses that can be sintered at low temperatures. In addition to LuAG: Ce phosphor, LuAG: Ce phosphor-in-LAS (LuAG: Ce-PiGLAS) has been successfully developed, which can withstand an 8.24-W laser irradiation without heat dissipation, achieving a luminous flux of 1248 lm and LE of 204 lm/W. Furthermore, a pre-thermal treatment was used to precipitate the lithium disilicate phase to enhance the resistance of the glass to laser ablation, resulting in a power increase to 8.62 W at 1485 lm and maximum LE increase to 212 lm/W with a 2.5% attenuation at 498 K. High-brightness illumination performance was demonstrated in both transmission and reflection modules. This study is anticipated to generate new prospects for PiG applications and accelerate the development of laser lighting.

Color Tunable Composite Phosphor Ceramics Based on SrAlSiN3:Eu2+/Lu3Al5O12:Ce3+ for High-Power and High-Color-Rendering-Index White LEDs/LDs Lighting.

Lu3Al5O12:Ce3+ phosphor ceramics were fabricated by vacuum sintering. On this basis, a bi-layer composite phosphor was prepared by low-temperature sintering to cover the phosphor ceramics with a layer of SrAlSiN3:Eu2+-phosphor-in-glass (PiG). The optical, thermal, and colorimetric properties of LuAG:Ce3+ phosphor ceramics, SrAlSiN3:Eu2+ phosphors and SrAlSiN3:Eu2+-PiG were studied individually. Combining the bi-layer composite phosphors with the blue LED chip, it is found that the spectrum can be adjusted by varying the doping concentration of SrAlSiN3:Eu2+-PiG and the thickness of Lu3Al5O12:Ce3+ phosphor ceramics. The maximal color rendering index value of the white LED is 86, and the R9 is 61. Under the excitation of a laser diode, the maximum phosphor conversion efficacy of the bi-layer composite phosphors is 120 lm/W, the Ra is 83, and the correlated color temperature is 4534 K. These results show that the bi-layer composite phosphor ceramic is a candidate material to achieve high color rendering index for high brightness lighting.

Cr3+-activated NaInSi2O6: An efficient broadband near-infrared phosphor with its applications in LED

A novel near-infrared (NIR) emitting Cr3+-doped clinopyroxene NaInSi2O6 phosphor is designed and synthesized by solid-state method. There are three absorption bands in the NaInSi2O6: 0.04Cr3+ phosphor, peaking at ∼300 nm, ∼470 nm and ∼690 nm, respectively. A broad emission band ranging from 700 nm to 1300 nm is detected at 466 nm excitation, peaking at 936 nm with a full width at half maximum (FWHM) of 151 nm. At the same time, the calculated weak crystal field strength of Cr3+ is 1.93 in the NaInSi2O6 host, resulting in its characteristic broadband emission. Furthermore, the internal quantum efficiency (IQE) and external quantum efficiency (EQE) of NaInSi2O6: 0.04Cr3+ are 68.9% and 27.4%. The integrated emission intensity of NaInSi2O6: 0.04Cr3+ at 423 K retains 55.2% of that at 293 K. By contrast, the NaInSi2O6: 0.04Cr3+-based phosphor-in-glass (PiG) exhibits better thermal stability (64.9%@423 K). A NIR phosphor-converted light emitting diode (pc-LED) was manufactured using a InGaN chip and NaInSi2O6: 0.04Cr3+, presenting the NIR output power of 30.47 mW@200 mA. Used as a NIR light source, the prepared pc-LED shows good promise in the fields of biological tissue imaging and night vision.

Excitability remodeling in Sm3+-doped aluminosilicate glass phosphors

Excitability of activator Sm3+ in full-band UV has been remodeled efficiently by introducing sensitizers Ce3+ and Sb3+ in multi-component-aluminosilicate (MAS) glass phosphors. The Ce3+-Sb3+-Sm3+ tri-doped MAS glasses not only exhibit amazing capability of capturing photons in UVC and UVB but also remarkably enhance the fluorescence emission effect of Sm3+ at the sensitized excitation wavelengths of 325 and 287 nm corresponding to Ce3+ and Sb3+ contributions. The determination of the optimal doping concentration of Ce3+-Sb3+-Sm3+ intensely depends on the energy transfer mechanism and the maximum sensitization coefficient of tri-doped MAS glass phosphors reaches 18.75. Robust corroborations of fluorescence images and dynamic video demonstrate that Ce3+-Sb3+-Sm3+ tri-doped MAS glass phosphors possess preeminent excitation response in the entire UV region. Further, the excellent sensitization and tunable excitation performance are achieved in MAS glass with high mechanical properties, which provide far-reaching research implications for the developing UV-induced optoelectronic devices of light conversion and laser illumination.

Inorganic remote glass film based on yellowish‐green (Y, Ba)3(Al, Si)5O12:Ce garnet phosphor for warm white LEDs

AbstractCompared with other fluorescent crystal phases, garnet has better structural stability in a glass matrix and renders precisely controllable emissions due to the abundant lattice control positions. In this work, we regulate the coordination field of Ce3+ ion based on the co‐substitution method and achieve the spectra regulation in the yellow–green range. We used Ba2+–Si4+ cations to replace Y3+–Al3+ cations in Y3Al5O12 (YAG) matrix to obtain blue‐shift of the emission peak from 552 to 539 nm. The centroid shift and crystal field splitting decrease with the decreasing covalency of the bond between the Ce3+ ion and the surrounding anions owing to the higher electronegativity of Si4+ ions than Al3+ ions. The corresponding fluorescent films were prepared by a low‐temperature co‐sintering process based on the as‐made Ba2+–Si4+ co‐substituted phosphor. X‐ray powder diffractometer and scanning electron microscopy images showed that the fluorescence crystals were less eroded and evenly dispersed in the glass matrix. Spectral analysis showed that the garnet phase was protected by using lead‐free borosilicate glass with a low melting point, and the quantum efficiency of phosphor‐in‐glass (PiG) retains 98% of the corresponding phosphor. By adjusting the ratio of garnet phosphor to commercial red nitride phosphors, a warm white fluorescence with a color rendering index of 80.3 and color temperature of 3899 K was obtained. The prepared warm white film has potential application value in the whole spectra field.

Orange-red-emitting (Sr,Ba)3SiO5:Eu2+ phosphor-in-glass film for enhanced color rendering of laser lighting

Nitride red-emitting materials exhibit severe luminance saturation and are thus not suitable for achieving enhanced color rendering in laser lighting applications. The silicate luminescent material (Sr,Ba)3SiO5:Eu2+ displays excellent stability and can emit orange-red light when excited by blue laser light, making it a promising candidate for realizing high-performance laser lighting. In this study, (Sr,Ba)3SiO5:Eu2+ phosphor-in-glass (PiG) films were prepared on a sapphire substrate, and the influences of preparation temperature, mass ratio of phosphor to glass frit (PtG ratio), and film thickness on the application performance of PiG film were analyzed. The (Sr,Ba)3SiO5:Eu2+ PiG film with a PtG ratio of 1:1 and a film thickness of ∼50 μm prepared at 475 °C exhibited optimal comprehensive luminescence performance. This film exhibited a luminous saturation threshold of 5.98 W/mm2, a maximum luminous flux of 372.3 lm, and a luminous efficiency of 62.3 lm/W at the luminous saturation threshold. The maximum luminous flux of the (Sr,Ba)3SiO5:Eu2+ PiG film was 77.6% higher than that of the CaAlSiN3:Eu2+ nitride PiG film. Finally, through the incorporation of green-emitting YAGG:Ce3+ phosphor into the (Sr,Ba)3SiO5:Eu2+ PiG film, laser-driven white light with a luminous flux of 531.7 lm and a high color rendering index (CRI) of 83.4 was realized.

Exploring interfacial reactions and optical properties of ZBLAN-based phosphor-in-glass color converters via spark plasma sintering for laser-driven lighting

Phosphor-in-glass (PiG) is extensively utilized as a color converter in laser-driven lighting. Despite its popularity, a noteworthy concern is the potential for interfacial reactions to occur between the phosphors and the glass matrix during high-temperature processing, leading to subsequent corrosion. Previous research suggests that spark plasma sintering (SPS) may effectively limit these reactions in silica glass-based PiGs. However, the reactivity of silica glass, lacking glass modifiers, towards phosphors is diminished, raising uncertainty about whether SPS can truly fabricate a PiG with improved interfacial morphology. Nonetheless, research pertaining to PiG fabrication using SPS with multi-component glass compositions remains scarce. In this study, an attempt is made to address this gap by employing a multi-component glass matrix - ZrF4–BaF2–LaF3–AlF3–NaF (ZBLAN), which is known for its high reactivity with phosphors, in the creation of PiGs through SPS. Lu3Al5O12:Ce3+ (LuAG) was embedded within ZBLAN glass, fabricated using SPS in merely 5 min at a temperature of 255 °C. The subsequent analysis focused on the interfacial microstructure and the optical properties of the thus prepared PiG samples. The results demonstrate that the lower-temperature and time-efficient sintering process of SPS successfully mitigate the interfacial reactions between the phosphor and the glass matrix. Consequently, a commendable luminous flux of 597 lm and luminous efficacy of 242 lm/W is achieved.

High luminous efficiency of a phosphor-in-glass plate by optimization of the glass and phosphor content for high-power LED applications

Generally, white light-emitting diodes (LEDs) are fabricated by combining blue LED chips with yellow phosphors. When fabricating white LEDs, the phosphor is typically mixed with an organic resin and applied to the LED chips as a paste. A phosphor-in-glass (PiG) plate can alternatively be used to address the poor high-temperature reliability of the paste method. However, because pores form in the PiG plate during the sintering process, this method results in a loss of optical efficiency. Accordingly, we aimed to improve the fluidity of glass and light efficiency by optimizing the sintering temperature of the glass powder and the phosphor content respectively for reducing internal porosity in the PiG. In this study, glass powder was sintered at different temperatures to produce glass plates, while also varying the phosphor content to fabricate PiG plates. The optimal light characteristics were realized with a glass sintering temperature of 640 °C and a phosphor content of 20 wt%.

Luminescence performance of Eu3+ doped 25La2O3-60Al2O3-15ZrO2 glass prepared by containerless method

Rare-earth metal Eu doped glass 25La2O3-60Al2O3-15ZrO2:xEu3+ (x = 0.1 wt%, 0.5 wt%, 1.0 wt%, 3.0 wt% and 5.0 wt%) was prepared by gas suspension containerless laser melting technology, which is transparent and has sphere ball shape. The glass shows excellent thermal stability although the temperature difference ΔT between crystallization initiation temperature To and glass transition temperature Tg (ΔT=To-Tg) is just between 48.6 ℃− 64.9 ℃, showing low glass forming ability and being difficult to prepare glass by traditional melt-quenching method. The Eu-doped glass preserves rather high transparency, and presents enhanced mechanical performance due to the Eu3+ doping, which improves glass network connectivity. Strong orange emission peak centered at 605 nm and red emission peak at 696 nm, and weak yellow emission peak centered at 582 nm and red emission peak at 646 are engendered under the excitation of 394 nm light, attributing to the 5D0→7F2, 5D0→7F4, 5D0→7F1, and 5D0→7F3 electron energy level transitions of Eu, respectively. The 25La2O3-60Al2O3-15ZrO2:xEu3+ phosphor glass has strong nearly standard red light with high color purity, which presents excellent candidate for red luminescent phosphor and shows potential application in white-light-emitting diode.

Cost-effective way of improving the optical properties of phosphor-in-glass by adjusting the particle size of glass powder

The effects of silicate glass particle size and Y3Al5O12: Ce3+ (YAG: Ce3+) phosphor doping concentration on the optical properties of phosphor-in-glass (PiG) samples were investigated. When the average particle size of glass powder was 160, 100, 60, and 30 μm, the transmittance of silicate glass with a thickness of 0.6 mm was 68%, 78%, 62%, and 54%, respectively. With the mixing of 4 wt% YAG: Ce3+ phosphor in each component of silicate glass, the transmitted luminous flux of PiG gradually increased with the increase of transmittance, reaching a maximum of 179.5 lm. Simultaneously, we found that with the increase in transmittance, the photoluminescence (PL) intensity of PiG gradually decreased; however, the total luminous flux of PiG has independent of transmittance. When the doping concentration of YAG: Ce3+ phosphor was 4 wt%, PiG achieved a maximum efficient white light emission of 212.61 lm/W under blue laser excitation at 2.31 W. All results indicate the outstanding feasibility of the prepared YAG-PiG in high-power/high-brightness white light-emitting diodes (WLEDs).

High reliability and luminance of the color wheel by phosphor-in-inorganic silicone

High reliability and luminance of the color wheel in a laser light engine (LLE) employing novel phosphor-in-inorganic silicone (PiIS) fabricated at the low temperature of 180°C for laser projector applications is presented and demonstrated for the first time. Yellow (Y3Al5O12:Ce3+) and green (Lu3Al5O12:Ce3+) phosphors were uniformly mixed by inorganic silicone, organic silicone, and glass to fabricate as a phosphor color wheel. The PiIS-based color wheels showed better thermal stability than the phosphor-in-organic silicone (PiOS), about 3-7 times less lumen loss and 7-8 times less chromaticity shift under accelerated aging at 350°C for 1008 hours. The advantage of the PiIS fabricated at a low temperature of 180°C enabled the achievement of excellent thermal performance, which was similar to the phosphor-in-glass (PiG) fabricated at a high temperature of 680°C. The good thermal stability of the PiIS can be attributed to the high glass melting temperature of up to 510°C. Low-temperature fabrication, excellent optical performance, and high reliability of the proposed PiIS-based color wheels benefit as promising candidates to replace the current PiOS or PIG-based color wheels in the LLE modules for the next-generation laser projector applications.

Preparation and Thermal Conductivity Enhancement of Boron Nitride Nano-Material PiG Composite

With the improvement of the conversion efficiency of LED chip and fluorescent material and the increasing demand for high-brightness light sources, LED technology has begun to move toward the direction of high-power. However, there is a huge problem that high-power LED must face with a large amount of heat generated by high power causing a high temperature thermal decay or even thermal quenching of the fluorescent material in the device, resulting in a reduction of the luminous efficiency, color coordinates, color rendering index, light uniformity, and service life of LED. In order to solve this problem, fluorescent materials with high thermal stability and better heat dissipation were prepared to enhance their performance in high-power LED environments. A variety of boron nitride nanomaterials were prepared by the solid phase-gas phase method. By adjusting the ratio of boric acid to urea in the raw material, different BN nanoparticles and nanosheets were obtained. Moreover, the control of catalyst amount and synthesis temperature can be used to synthesize boron nitride nanotubes with various morphologies. By adding different morphologies and quantities of BN material in PiG (phosphor in glass), the mechanical strength, heat dissipation, and luminescent properties of the sheet can be effectively controlled. PiG prepared by adding the right number of nanotubes and nanosheets has higher quantum efficiency and better heat dissipation after being excited by high power LED.

Fabrication of phosphor in glass using waste glass for automotive lighting application

With advancement of technology, requirements for light-emitting devices are increasing. Various types of packaging technologies have been suggested to improve the performance of light-emitting diode (LED). Among them, phosphor in glass (PiG) is attracting attention due to its manufactural facility and easily tunable characteristics. As PiG draws increasing attention, research on glass materials is also being actively conducted. However, studies about glass in the field of phosphor are mainly conducted on fabrication. Only a few studies about recycling have been reported. Thus, the objective of this study was to recycle waste glass discarded in other fields due to breakage and failure and use it to fabricate phosphor in glass. Cylindrical waste glass was pulverized into powder with an average size of 12 μm, mixed with a phosphor and sintered to be reborn as a phosphor in glass to broaden the recycling route for waste glass.

Phosphor-in-glass with time-evolving multicolor luminescence for dynamic anticounterfeiting

The conventional luminescent materials used in the anticounterfeiting field generally exhibit unicolor output and a single-wavelength excitation mode, resulting in a poor anticounterfeiting effect. Herein, we successfully achieved a new transparent SrAl2O4:Eu2+,Dy3+/CaAlSiN3:Eu2+ phosphor-in-glass (PiG) with dynamic luminescence color variation from red to yellow in hundreds of seconds during the ultraviolet lamp irradiation and green persistent luminescence (PersL) after ceasing excitation. Additionally, the prepared PiG owns excitation wavelength- or doping weight ratio-dependent color-tunable luminescence. As a proof-of-concept experiment, the specially designed SrAl2O4:Eu2+,Dy3+/CaAlSiN3:Eu2+ PiG based flower patterns exhibit dynamic luminescence color variation under a simple ultraviolet lamp, and can be observed for quick discrimination. This work exploits a new perspective for the design of dynamic multicolor anticounterfeiting materials.