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Issue 10 ， 2021
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Research Progress on Optical Quenching of Ce3+- and Eu2+-doped Luminescent Materials Enhanced Publication
Abstract：Ce3+- and Eu2+-doped luminescent materials featuring high absorbance, broad emission band, short decay time, and tunable emission spectra, are ideal candidates for laser lighting and display applications. However, luminescence quenching of Ce3+- and Eu2+-doped luminescent materials under laser excitation severely restricts the luminous efficacy and luminance of laser-driven lighting devices. As a rule of thumb, the luminescence quenching is attributed to thermal quenching. However, recent studies have found that even if the thermal quenching is controlled, the high-intensity excitation light itself can lead to a significant decrease in the luminous efficiency of luminescent materials. This non-thermal luminescence quenching effect can be referred to as optical quenching. This article briefly reviews the latest research progress of four known optical quenching effects, namely, ground-state depletion, excited-state absorption, energy-transfer upconversion, and optically stimulated luminescence, and the prospects of studies on optical quenching are outlined.Keywords：laser lighting and display;luminescent materials;optical quenching;optical saturation- 2014
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Published：2021-10-17 -
Abnormal Thermal Quenching Effect of High Power Density Excited Fluorescent Materials Enhanced Publication
Abstract：Thermal quenching is a phenomenon that the luminescence intensity of fluorescent conversion materials decreases with the increase of temperature, and it seriously affects the performance of the devices and limits the applications in high power LED/LD lighting. However, the luminescence intensity of some fluorescent materials often increases with the rise of temperature, which is named as the abnormal thermal quenching effect. As an effective way to improve the performance of luminescent materials and devices, the abnormal thermal quenching effect has been widely studied. In this paper, the research status and application of fluorescent materials with abnormal thermal quenching effect was reviewed, the mechanism of abnormal thermal quenching effect was illustrated, and its future development trend was prospected. This review will help to develop new luminescent materials with better abnormal thermal quenching characteristics to meet the application requirements of high efficiency and high power LED/LD lighting devices.Keywords：high power density;LED/LD lighting;thermal quenching phenomenon;abnormal thermal quenching effect- 1059
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Published：2021-10-17 -
Synthesis and Performance of La3Si6N11∶Ce3+ Phosphor-in-glass Films for Laser Lighting Applications Enhanced Publication
Abstract：The development of high-performance color converters is the key to laser lighting technology. Due to the high-power excitation from the laser lighting, the color converters must have high thermal conductivity and excellent high-temperature stability. The phosphor-in-glass(PiG) film is promising for high-power laser lighting applications due to its excellent comprehensive performance. The traditional Y3Al5O12∶Ce3+(YAG∶Ce3+) PiG film can hardly achieve high-quality white lighting due to its poor color rendering. Compared with YAG∶Ce3+, nitride phosphor La3Si6N11∶Ce3+(LSN∶Ce3+) exhibits broader emission spectrum and better thermal quenching behavior. In this work, LSN∶Ce3+ PiG film was prepared on a blue-pass(BP) optical film coated high thermal conductivity sapphire substrate. The effects of sintering temperature, ratio of phosphor to glass powder(PtG), film thickness, and BP optical film on the luminescence properties of final samples were studied. With the optimized synthetic process, LSN∶Ce3+ PiG film of excellent properties can be achieved at 800 ℃, 1∶1 PtG ratio and 50 μm thickness. The sample could be excited by a blue-laser with high flux density up to 12.73 W/mm2 and showed a luminous efficiency of 157.6 lm/W. Furthermore, the color rendering index of LSN∶Ce3+ PiG film can reach 74.9, which is 9% higher than that of YAG∶Ce3+, indicating great potential in high power laser lighting applications with high color rendering.Keywords：phosphor-in-glass(PiG) film;laser lighting;blue-pass(BP) optical film;sapphire substrate- 901
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Published：2021-10-17 -
Lu2SrAl4SiO12∶Ce3+ Phosphor in Glass Film-on-sapphire and Its Application to Laser Lighting Enhanced Publication
Abstract："Laser+conversion material" strategy has become one of the hotspots in lighting field. Herein, a phosphor in glass film sintered on sapphire plate(PiG film-on-SP) embedded with Lu2SrAl4SiO12∶Ce3+(LSAS∶Ce3+) phosphor was prepared via low temperature co-sintering method.It was demonstrated that LSAS∶Ce3+ phosphor was less corroded by glass components during co-sintering, and so, the high quantum efficiency(~90%) was retained. Meanwhile, this material has better thermal quenching performance than commercial YAG∶Ce3+phosphor. The fluorescence integral intensity at ~300 ℃ remains~70% of that at room temperature. "Luminescence saturation" takes place under 3.0 W/mm2 blue laser irradiation, and the corresponding luminous flux is 100.49 lm, applicable to in-door scenarios. It was speculated that thermal saturation and optical saturation simultaneously occur, restricting the achievable brightness.After optimization of material composition, preparation process, as well as employing the light field regulation method, LSAS∶Ce3+PiG film-on-SP with higher brightness will be hopefully applicable to out-door scenarios.Keywords：laser lighting;phosphor;luminescent glass ceramics;garnet structure- 579
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Published：2021-10-17 -
Hot Isostatic Pressing Post-treatment and Performance of Red-emitting AlN-CaAlSiN3∶Eu Composite Phosphor Ceramics Enhanced Publication
Abstract：The previously reported highly thermal conductive red-emitting AlN-CaAlSiN3∶Eu composite phosphor ceramic is difficult to improve the luminescence performance due to the carbon contamination problem caused by spark plasma sintering(SPS). In this paper, hot isostatic pressing(HIP) post-treatment is used to prepare red-emitting phosphor ceramics with excellent luminescence performance and extremely high saturation threshold, which promotes the development of high-power laser lighting. The SPS sintered samples were treated by HIP in N2 atmosphere. The experimental results show that the luminescence intensity and quantum efficiency of the samples are doubled after HIP post-treatment, the luminous flux is increased by 51%, and the saturation threshold is increased by more than 15%. The sample with the best performance remains intact without luminance saturation when the incident laser power is as high as 15 W, and the luminous flux is up to 197 lm.Keywords：laser lighting;nitrides;phosphor ceramics;hot isostatic pressing;luminance saturation- 531
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Published：2021-10-17 -
Preparation of Ce3+∶Y3Al5O12-Al2O3 Nano Ceramics by Aerodynamic Suspension Solidification for LDs-driven Lighting Application Enhanced Publication
Abstract：Obtaining high luminance light source by emitting and excitation of blue-emitting laser diodes(LDs) has become an important research direction in the field of high-power lighting and display. This field involves multiple disciplines including luminescent materials, optical engineering, mechanical structure and circuit design, among which optical design and color conversion materials and devices are key technologies. Due to their high research and production expenditure, they have become one of the factors limiting the realization of large-scale and widespread applications. In this paper, the rapid and low cost preparation of Ce3+∶Y3Al5O12-Al2O3(Ce3+∶AY26)based phosphor nanoceramics by pneumatic suspension solidification was studied. The luminescence performance was optimized by adjusting Ce3+ doping concentration for achieving higher quantum efficiency (87.4%). As the second phase, Al2O3 not only can play the role of scattering center and improve the conversion efficiency and beam uniformity of laser excitation, but also has higher thermal conductivity, which plays a key role in improving the thermal stability, and Ce3+∶AY26 phosphor nanoceramics still hold 95% of room temperature quantum efficiency when temperature reached 200 ℃. Through the transmission laser illumination test system, the optical and color properties of 1.5 mm thick phosphor nanoceramics sheet with LE of 174 lm·W-1 and 1.5 mm semispherical phosphor nanoceramic under high power density blue laser irradiation were studied. Hemispherical phosphor nanoceramics prepared by containerless solidification technology are expected to simplify the optical structure design of transmission laser illumination modules from the point of view of material preparation methods and have great application potential in the future.Keywords：Containerless Solidification;Ce3+∶Y3Al5O12-Al2O3;phosphor nanoceramics;LDs-driven Lighting- 344
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Published：2021-10-17 -
Green-yellow Emission Ce∶LuAG Transparent Ceramics for High-brightness Solid-state Lighting Enhanced Publication
Abstract：A series of (CexLu1-x)3Al5O12(Ce∶LuAG, x=0.0005, 0.001, 0.002, 0.003, 0.004) transparent ceramics were prepared via high-temperature reactive sintering under vacuum. The in-line transmittances of these transparent ceramics are higher than 75% at 500-800 nm with a thickness of 1.0 mm. Absorption and emission properties of ceramics with different Ce3+ concentrations excited by 454 nm blue LED were investigated. An adjustable correlated color temperature(CCT)(5 653-7 433 K) was obtained. The as-prepared ceramics show remarkably superior thermal and luminescent properties: a low thermal quenching(7% drop at 225 ℃), and a high luminous efficacy of 179 lm/W were obtained in the 0.1%Ce∶LuAG ceramics(1.0 mm thick) coupled with commercial blue InGaN LED chips, which also shows increasing emission intensity with increasing input power(up to 3.6 W). A high flux of 3 646 lm was obtained with robust Ce∶LuAG ceramics irradiated with a high laser power density of 24.6 W/mm2. Obviously, the fabricated transparent Ce∶LuAG ceramics are quite prospective as a highly efficient and thermally robust green-yellow color converter for high-power solid-state lighting(SSL) application.Keywords：luminescence saturation;Ce∶LuAG ceramics;color converter;high-brightness- 562
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Published：2021-10-17 -
Recent Progress of LuAG∶Ce3+ for White Laser Diode Lighting Application Enhanced Publication
Abstract：Laser-diodes(LDs) combined with color converters are regarded as the next-generation lighting source. Color converters play important roles in determining the luminous efficiency, color quality, and long-term stability of the LDs lighting. Recently, kinds of green/yellow/red color converters were adopted to enrich spectral components and achieve a high color quality in the LDs lighting. Among them, the color rendering index of the LDs lighting can be greatly improved by using Lu3Al5O12∶Ce3+(LuAG∶Ce3+) and red color converters. LuAG∶Ce3+ is regarded as one of the best green color converters. It has high thermal stability and saturation threshold under high-power LDs. To mitigate the thermal effect induced by the high-power density of blue LDs, remote encapsulations of single-crystal phosphors, (transparent) ceramic phosphors, phosphor in glasses/films are proposed. This paper reviews and summaries recent progress of LuAG∶Ce3+ for LD lighting application and puts forward the prospect of the future development direction.Keywords：LuAG∶Ce3+;ceramic phosphors;phosphor in glass;phosphor film;white laser diode lighting- 590
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Published：2021-10-17 -
K2SiF6∶Mn4+ Luminescent Glass Ceramics Applicable to Laser Lighting Enhanced Publication
Abstract：Towards the strong market demand for high power, high quality lightings, it is particularly important to develop red fluorescent glass ceramic with excellent optical performance and stability to improve the color rendering index(CRI) of white light. In this work, a glass ceramic embedded with commercial K2SiF6∶Mn4+ (KSF) red phosphor was prepared via a low-temperature co-sintering method. The results show that the thermal erosion effect of the precursor glass melt on KSF phosphor is limited during co-sintering, so the optical properties of the phosphor are retained. Compared with the initial phosphor, the thermal quenching properties of glass ceramics are greatly improved. The fabricated laser lighting source exhibits lumen of 32.77 lm, correlated color temperature of 5 073 K, CRI of 74.86, and chromaticity coordinate of (0.341,0.321), under the excitation of 55.56 W/cm2 blue laser diode(LD) power density. After further optimization of systematic thermal management, KSF fluorescent glass ceramic is expected to be applied in the field of high power indoor lighting.Keywords：K2SiF6∶Mn4+ phosphor-in-glass;low melting glass;laser lighting- 441
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Published：2021-10-17 -
Preparation and Luminescent Properties of Rb2SiF6∶Mn4+ Single Crystal for Laser Lighting Enhanced Publication
Abstract：Laser lighting is one of the important developing directions in solid-state lighting in the future. At present, the main stream laser lighting devices are fabricated by yellow/green ceramics or crystals, which show high color temperature and low color rendering index due to the insufficient red-light component of a single material. Herein, Rb2SiF6∶Mn4+(RSFM) red-emitting single crystal with high efficiency and high stability was prepared by a simple solution growth method. The RSFM single crystal shows broadband blue light absorption(~450 nm) and narrowband red emission(~630 nm). The external quantum efficiency(EQE) of RSFM crystal is up to 55.8%, showing great potential in laser lighting to improve the color quality. Under the excitation of 7 W/mm2, a warm white laser diode device with high luminous efficiency of 104.3 lm/W, correlated color temperature of 2 633 K and a color rendering index of 78.3 is presented. The development of high-performance Mn4+-activated fluoride single crystals is expected to provide new insights into the development of highly efficient and stable materials for advanced lighting applications.Keywords：Mn4+-Doped;fluorides;Red-emitting Single Crystal;laser lighting- 373
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Published：2021-10-17 -
Research Progress on Preparation Methods of Perovskite Nanocrystals Embedded Glass Enhanced Publication
Abstract：Owing to the high luminous efficiency and tunable emission spectra, all-inorganic perovskite nanocrystal is one of the research hotspots in the field of optoelectronics. However, the poor stability has always hindered their practical applications. Embedding the perovskite nanocrystals into the glass matrix can not only effectively improve the physical and chemical stability, but also retain the original luminescence properties, which has drawn much attention from researchers. The research progress of perovskite nanocrystals embedded glass will be reviewed in this paper, and the preparation methods and application fields are described. Finally, we will summarize the problems and prospect the future development of perovskite nanocrystals embedded glasses.Keywords：all-inorganic perovskite;nanocrystalline;luminescent glass;preparation methods- 519
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Published：2021-10-17 -
Broadband-emitting Remote Color Convertors for High Color Rendering Laser-driven Lighting Enhanced Publication
Abstract：Featuring high thermal stability, strong heat bearing capacity and stable fluorescence property, the next-generation laser diode(LD) solid state lighting, structured by remote color convertors phosphor ceramics, phosphor in glass and phosphor crystals, has wide application in automobile headlamps, projection display, and space navigation lighting. However, the urgent bottleneck of this technology is hard to achieving broadband-emitting in visible light, resulting in poor lighting quality. In this paper, the recent progress of remote color convertors for high color rendering index(CRI) and low correlated color temperature(CCT) laser white light source is reviewed and summarized, and the reason for poorer lighting quality under the excitation of high lumen density laser is analyzed. The electronic luminescence(EL) spectrum regulation and improvement effect of CRI and CCT of laser lighting source are illustrated. Some important topics for color convertors, such as efficiency enhancement, high temperature quenching and evolution standard are also discussed. Finally, the development trend of remote color convertors with broadband-emitting in solid state lighting and display is prospected.Keywords：laser-driven lighting;Broadband-emitting;Light quality;solid solution/doping;multi color combination- 694
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Published：2021-10-17 -
Yttrium Aluminum Garnet Phosphor-in-glass with Improved Color-rendering for Laser Lighting Enhanced Publication
Abstract：Due to the spectrum defect of the red and green light component, the Y3Al5O12∶Ce3+(YAG∶Ce3+) phosphor-in-glass(PiG) cannot be applied in high-quality laser lighting. Based on the yttrium aluminum garnet luminescent material with wide spectrum, high luminous efficiency and high stability, the green-emitting Y3(Ga,Al)5O12∶Ce3+(YAGG∶Ce3+) and orange-emitting (Y,Gd)3Al5O12∶Ce3+ (GdYAG∶Ce3+) phosphors were used as raw materials to fabricate PiG, and the PiG sample with improved color-rendering was achieved. The effects of fabrication temperature, phosphor-to-glass ratio, YAGG∶Ce3+/GdYAG∶Ce3+ ratio, and the thickness on properties of PiG samples were studied in detail. By optimizing synthetic conditions and PiG components, the color rendering index (Ra) of achieved PiG can reach 79.7, showing 13.7% improvement compared with that of YAG∶Ce3+ PiG. The luminescence saturation threshold of PiG sample with optimal Ra is 1.63 W/mm2, and the luminous efficacy can reach 163.14 lm/W, suggesting a promising application in laser lighting for achieving better lighting effects.Keywords：laser lighting;yttrium aluminum garnet;phosphor-in-glass;high color-rendering- 491
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Published：2021-10-17 -
Preparation and Laser-driven Lighting Application of High-CRI White Light PiG Film Enhanced Publication
Abstract：In this paper, by the way of mixing glass powder with yellow-green(535-550 nm) and red(660 nm)-emitting phosphors, and then coated on a sapphire wafer by screen-printing, the PiG film(Phosphors in glass flim, PiGF) with white light and high CRI is successfully prepared at a lower sintering temperature. The effects of different ratios of glass/phosphor and G/R phosphors(535 nm/660 nm) on PiGF's CCT, CRI, luminous efficiency(LE), etc. are systematically studied. The results show that the prepared PiGF can generate white light with a CCT of 5 500 K and a high CRI of 92, when the mass ratios of phosphor /glass powder and G /R phosphor are fixed at 1∶4 and 9∶1, respectively, under the excitation of blue laser diodes(LD, 455 nm) with an electric power of about 12.5 W. The results show that PiGF has great practical application in high CRI and white light laser-driven lighting.Keywords：fluorescent film;laser-driven lighting;high CRI;phosphors in glass flim(PiGF)- 496
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Published：2021-10-17 -
Scattering Control Strategies in Phosphors for Laser Lighting Application——Mini Review Enhanced Publication
Abstract：Novel ultra-high-luminance laser lighting technique based on pumping phosphor by laser diode shows broad application prospect. To achieve high-luminance, a laser lighting luminaire is essential to possess high luminous flux and small light-emitting area. Therefore, it is essential for phosphor to possess both high saturation threshold and strong spot size limitation ability. The microstructure design and scattering control in phosphor materials show potential to solve this problem. In this paper, the studies on spot size of laser lighting were introduced, and the effect of scattering coefficient on the luminescence properties was discussed. After that, some key techniques including measurement and simulation on spot size were presented. Lastly, some future directions were prospected.Keywords：laser lighting;phosphor;scattering coefficient;spot size;high-luminance- 538
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Published：2021-10-17 -
Effect of Laser Spot Regulation on Evaluation of Laser Phosphors Enhanced Publication
Abstract：The newly-emerging laser lighting technology shows great advantages of high brightness, high luminous flux and long lifetime, which therefore attracts more attention for use in high-beam headlamps, cinema projectors and endoscopy. In this technology, the size of laser spots has a large effect on the proper evaluation of laser phosphors, but it is usually neglected and lack of deep investigations. In this paper, we conducted a survey on the influence of the spot size on the maximum output luminous flux, luminous saturation threshold, color temperature, color coordinates, and light uniformity of Y3Al5O12∶Ce3+-Al2O3(YAG∶Ce-Al2O3) phosphor films for laser lighting. It reveals that the laser spot size does have a vital effect on optical properties of laser phosphors, and needs to be carefully considered. This work provides a general guideline for standardizing the performance evaluation of laser phosphors.Keywords：laser lighting;laser phosphor;laser spot regulation;optical performance- 704
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Published：2021-10-17
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