High-power White Light-emitting Diodes Research Articles

Life cycle assessment of high-power white LEDs for indoor lighting in the context of Hong Kong

The introduction of white light-emitting diodes (LEDs) is one of the key innovations that has revolutionized the lighting industry due to its multiple benefits. Despite their advantages, there is a gap in the environmental impact information of the recently developed high-power LED products within the whole lifecycle, which is a key step to achieve sustainable and green development. This life cycle assessment (LCA) is conducted by considering the cradle-to-grave system boundary. The functional units considered are a LED and compact fluorescent lamp (CFL) of 40 million lumen-hours (lm-h) used for indoor applications over an operating time of 20 000 h. In this study, the LCA was carried out using the SimaPro software and built-in ecoinvent database V2.2 with appropriate life cycle inventory data. The analysis results indicate that: (1) the LED-package has a dominant environmental impact followed by the LED driver while the housing and corrugated-board packaging materials showed the least negative effect to the ecosystem during the manufacturing phase. On the contrary, the CFL drivers are dominant followed by the light sources in the case of CFLs. From the lifecycle stages, the usage-phase showed a predominant environmental effect, mainly due to the energy consumption and sources of energy production. (2) A scenario analysis on the sources of electricity production revealed that prospective sources (70% natural gas, 25% nuclear and 5% pumped storage) of energy production lowered the environmental impact compared to the current electricity mix. These proposed electricity generation production sources provide a 61% reduction in the global warming potential in light sources for Hong Kong.

Recent Advances in Preparing Transparent Phosphor Ceramics for High-Index Color Rendering and High-Power Lighting.

In recent years, high-power white light-emitting diode (wLED)/laser diode (wLD) lighting sources based on transparent phosphor ceramic (TPC) materials have attracted increasing application interest in automotive headlights, projection displays, and space navigation lighting due to their superior brightness, lighting distance, compactness, lifespan, and environmental resistance compared with the widely used phosphor-converted wLEDs. However, preparing TPC-converted wLEDs/wLDs with high color rendering index (CRI) remains a huge challenge, which limits their widespread application. In this review, we summarize the recently adopted strategies for constructing TPCs to develop high-power wLEDs/wLDs with high CRI values (>75). The construction protocols were categorized into four groups: host regulation, red-emitter doping, host regulation/red-emitter doping combination, and composite structure design. A comprehensive discussion was conducted on the design principles, photoluminescent properties, and device performances for each strategy. The challenges and future trends of high-power and high-CRI wLEDs/wLDs based on TPCs are also discussed toward the end of this review.

A Robust Anti-Thermal-Quenching Phosphor Based on Zero-Dimensional Metal Halide Rb3InCl6:xSb3.

High-power phosphor-converted white light-emitting diodes (hp-WLEDs) have been widely involved in modern society as outdoor lighting sources. In these devices, due to the Joule effect, the high applied currents cause high operation temperatures (>500 K). Under these conditions, most phosphors lose their emission, an effect known as thermal quenching (TQ). Here, we introduce a zero-dimensional (0D) metal halide, Rb3InCl6:xSb3+, as a suitable anti-TQ phosphor offering robust anti-TQ behavior up to 500 K. We ascribe this behavior of the metal halide to two factors: (1) a compensation process via thermally activated energy transfer from structural defects to emissive centers and (2) an intrinsic structural rigidity of the isolated octahedra in the 0D structure. The anti-TQ phosphor-based WLEDs can stably work at a current of 2000 mA. The low synthesis cost and nontoxic composition reported here can herald a new generation of anti-TQ phosphors for hp-WLED.

High-performance luminescence of europium ion-activated Na2O-CaO-SiO2 system glass-ceramics through component regulation and crystallization process optimization strategies

Luminescent glass-ceramics has garnered significant attention within the research community owing to its exceptional characteristics, including robust chemical stability, outstanding thermal stability, and efficient thermal conductivity. However, persistent challenges include issues related to suboptimal luminous efficiency and color rendering index. In the context of this research endeavor, we have achieved a noteworthy achievement by successfully fabricating a novel variant of glass-ceramics doped with both Eu2+ and Eu3+ ions within the Na2O-CaO-SiO2 system glass. This innovative glass-ceramics composition encompassed Na4Ca4Si6O18 crystals, characterized by grain sizes <110 nm. Our investigations, featuring comprehensive optical spectra analysis and detailed morphological examinations, have provided substantial evidence indicating the preferential occupation of Eu3+ ions in the Ca2+ sites residing within the Na4Ca4Si6O18 crystal lattice, conversely, it is possible that the distribution of Eu2+ ions occurred within the glass matrix. Additionally, it is worth noting that this glass-ceramic material demonstrated a heightened excitation efficiency when subjected to 464 nm blue light, surpassing its performance with 393 nm violet light. Detailed fluorescence spectral analysis unveiled the impressive internal quantum efficiency of the glass-ceramics, reaching an impressive 80.27%, and this glass-ceramics exhibited remarkable fluorescence thermal stability at 150 °C, preserving approximately ∼75% of its luminescent intensity at room temperature. Furthermore, we have encapsulated the white light-emitting diode (W-LED) device, integrated with a 460 nm LED chip, optimized glass-ceramics, and YAG: Ce3+ phosphor. The outcomes were characterized by the warm white-light emission, suitable chromaticity coordinates, a high color rendering index (approximately 85.4), and impressive luminous efficiency (up to 112.47 lm/W). In summary, these findings unequivocally underscore the substantial potential of glass-ceramics in the realm of high-power W-LED lighting applications.

In-Situ early anomaly detection and remaining useful lifetime prediction for high-power white LEDs with distance and entropy-based long short-term memory recurrent neural networks

High-power white light-emitting diodes (LEDs) have demonstrated superior efficiency and reliability compared to traditional white light sources. However, ensuring maximum performance for a prolonged lifetime use presents a significant challenge for manufacturers and end users, especially in safety–critical applications. Thus, identifying functional anomalies and predicting the remaining useful lifetime (RUL) is of enormous importance in the operational longevity of the device. To address such challenges, this study proposes a combination of distance-based Mahalanobis distance (MD), entropy generation rate (EGR), and deep learning models for improved anomaly detection and RUL prediction accuracy. Unlike conventional health indicators based on luminous flux data that are challenging to monitor relevant optical performance, the MD and EGR methods are employed to extract in-situ monitored thermal and electrical data as new health indicators. Long short-term memory recurrent neural networks (LSTM-RNN) and convolutional neural networks (CNN) are established to detect anomalies and predict the RUL. The accelerated degradation tests of 3 W high-power white LED have been conducted, and the online and offline collected experimental data are deployed for model development and performance evaluation. The performance of the proposed methods is compared against the Illuminating Engineering Society of North America (IESNA) TM-21 method. The results indicate that LSTM-RNN, when combined with either MD or EGR, can detect anomalies with significantly fewer data (70 %) than is typically required. Furthermore, a significant improvement in prediction accuracy in RUL prediction based on MD and EGR-constructed time series health indicators and employed with the LSTM-RNN model demonstrates the effectiveness of the proposed methods.

Early failure of high-power white LEDs for outdoor applications under extreme electrical stress: Role of silicone encapsulant

Solid state lighting systems have deeply penetrated the market and are widely available. White light emitting diodes (LEDs) are based on a gallium nitride blue-emitting chip and a phosphor-based layer is used to convert blue radiation to white light, in combination with an optical system to enhance light extraction. High temperatures can be detrimental for LED reliability, resulting in a gradual or catastrophic failure. Therefore, the design of such devices, especially in relation to use cases that require operation at high current and temperature levels, needs to be based on reliability considerations.In this work we analyze the robustness of high power white LEDs submitted to driving currents exceeding the nominal levels by means of electrical and optical characterization, as well as on failure analysis techniques. The results highlight a significant degradation of the main optical parameters (luminous flux, color coordinates, correlated color temperature, …). Device cross sectioning highlighted a heavy darkening of the silicone material in the overstressed devices, and a delamination of the phosphors. Raman spectroscopy analysis highlighted an enhancement in luminescence of degraded samples. Such degradation was ascribed to the high temperature reached by the LEDs during the stress, that caused the degradation of the silicone lens; the process can be enhanced by the low efficiency of the phosphors and LEDs at high temperatures, resulting in a stronger heating of the devices.

Spatial uniformity of the spectral radiance by white LED-based K&lt;sub&gt;2&lt;/sub&gt;CaP&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;7&lt;/sub&gt;:Ce&lt;sup&gt;3+&lt;/sup&gt;, Tb&lt;sup&gt;3+&lt;/sup&gt; phosphor

The K2CaP2O7:Ce3+, Tb3+ (Ce/Tb-KCPO) phosphor with blue-to-green emission is introduced in this study. The synthesis of the phosphor is carried out with the solid-state approach. The phosphor characteristics, including X-ray diffraction, luminescence lifespan, and thermal stability are measured and examined. The data show that Ce/Tb-KCPO phosphor displays a broadband emission from blue to green when excited by ultraviolet source. Besides, the ion Ce3+ strengthen the emission of Tb3+ ion through an efficient energy-transfer mechanism, which is estimated about 82.51%. The main electric interaction responsible for this Ce/Tb energy transfer is the dipole-quadrupole one. The phosphor also benefits the luminous intensity and color uniformity of the light-emitting diodes (LED) white-light output. Therefore, the Ce/Tb-KCPO phosphor can be a potential material for high-power white light-emitting diodes (WLED).

Highly crystalline Y3Al5O12:Ce3+ phosphor-in-silica glass ceramics for high-power solid-state lighting

The pursuit of high-brightness solid-state lighting (SSL) stimulates the development of all-inorganic color converters with high robustness. It is required that the fluorescent material is able to cope with the extreme condition generated from the irradiation of high-power-density excitation light. As such, in this work, we developed a new composite color converter, i.e., Y3Al5O12:Ce3+ phosphor-in-silica glass ceramic (YAG:Ce3+ PiSGC). Remarkably, the amorphous SiO2 matrix spontaneously transforms into tetragonal SiO2 crystallites during co-sintering with crystallization fraction reaching up to >90% (almost full ceramization). The activation energy for crystallization Ec and Avrami index n of amorphous silica oxide are 298.5 kJ/mol and 1.71, indicating the diffusion-controlled glass crystallization mechanism. The fabricated prototype high-power phosphor-converted white light-emitting diode (pc-wLED) and phosphor-converted white laser diode (pc-wLD) based on YAG:Ce3+ PiSGC show satisfactory photometric/colorimetric parameters. The developed color converters have combined merits of environmental protection property, cost-effective manufacturing, good luminescent performance, and easy scalability. This study highlights a new kind of opto-functional composite material and its application as an efficient color converter in high-power solid-state lightings.

Stabilization of CsPbBr3 Nanocrystals via Defect Passivation and Alumina Encapsulation for High-Power Light-Emitting Diodes

The instability of inorganic cesium lead halide perovskite quantum dots (QDs) limits their commercial applications. Here, a streamline surface nanotailoring strategy combining defect passivation and alumina infiltration and encapsulation via atomic layer deposition was employed to improve the luminescence properties and stability of QD films. Didodecyl dimethyl ammonium bromide with oleic acid pretreatment was used to reduce nonradiative recombination and photoluminescence quenching through strong bonding. Al2O3 infiltrated through the gaps between the QDs with ng precision control and formed a dense encapsulation barrier, which separated QDs from the influence of the external environment. The fluorescence lifetime and the overall stability of the obtained QD films were greatly improved, which have application prospects in high-power white light-emitting diodes.

Analysis of thermal chromaticity stability, energy transfer and colour tunablity of Dy3+-Eu3+ doped BBZL glasses for high-power W-LED applications

A family of highly thermal chromatic stable Dy3+-Eu3+ doped B2O3-Bi2O3-ZnO-Li2O (BBZL) glass samples was synthesised using the high-temperature melt quenching technique. The optical and thermal stability properties of the samples were analysed using their fluorescence spectra at various temperatures, fluorescence lifetime decay times and colour coordinates. The Dy3+-doped BBZL (BBZL: Dy) glass samples generated cold white light when exposed to ultraviolet (UV) light, while the Dy3+-Eu3+-doped BBZL (BBZL: DyEu) glass samples emitted neutral and warm white light, which can be attributed to the introduction of Eu3+ that substantially enhanced the colour rendering of samples. An overlap of the excitation-emission spectra of Eu3+ and Dy3+ indicated an energy transfer between Dy3+ and Eu3+. Under a 350 nm excitation, the fluorescence lifetime of BBZL: DyEu decreased from 0.5348 to 0.3642 ms. Using the Dexter theory, the energy transfer between Dy3+ and Eu3+ was demonstrated to be an electric dipole-electric dipole leap. The chromaticity shifts of BBZL: DyEu were 8.60 × 10−4 and 9.40 × 10−4 at 448 and 498 K, respectively, reflecting the high thermal stability of the sample chromaticity. The study demonstrated that Dy3+-Eu3+ doped borate glasses can be used as tunable luminescent materials in high-power white light-emitting diodes to mitigate the chromaticity shift in fluorescent materials at high temperatures.

Opto-Thermal Performances Investigation of High-Power WLEDs With Different Reflective Dams

Reflective dam is a common structure in white light-emitting diodes (WLEDs) packaging due to its advantages of light regulation, heat conduction, and enhanced packaging efficiency. In this work, the opto-thermal performances of high-power WLEDs with different reflective dams were investigated. The dichromatic light is closest to the natural white light when the phosphor concentration was set at 7 wt% from 5 to 12 wt%. As the WLED modules with different dam materials (Cu, Al, and Al2O3 ceramic) were fabricated and compared, the results showed that the WLED with Al2O3 reflective dam presents higher luminous efficiency (LE) of 132.37 lm/W and lower correlated color temperature (CCT) of 5633 K at a driving current of 350 mA. Besides, the Al2O3 reflective dam has a high reflectance of 95.2% from 400 to 800 nm. In addition, in the test of thermal performance, the stable temperature of the WLED module packaged with the Cu reflective dam is 162 °C at the current of 2000 mA, which shows lower surface temperature and displays better heat dissipation performance than the Al dam and the Al2O3 ceramic dam.

K2SiF6:Mn4+ significantly improves water resistance and luminescence performance by coating green emission graphene quantum dots

In order to enhance the luminescent thermal stability and water resistance of K2SiF6:Mn4+, we proposed a simple hydrothermal method to synthesize K2SiF6:0.06Mn4+@GE-GQDS (6 mg/mol) (GE-GQDs: green emission graphene quantum dots) red emitting phosphor with outstanding water resistance. The emission intensity of the sample coated with the GE-GQDs still maintains 87.74% of the initial one after immersion for 360 min, while the uncoated K2SiF6:0.06Mn4+ sharply decreases to 11.26%. Another impressive phenomenon is that due to the negative thermal quenching (NTQ) effect, the luminescent thermal stability of the coated sample is also significantly improved, and the integrated photoluminescence (PL) intensity at 180 °C is 238% of that at 25 °C. In the meantime, the integrated PL intensity of the coated samples is 2.55 times that of K2SiF6:0.06Mn4+ under room temperature. Based on experimental results, it is suggested that after coating with GE-GQDs, a surface protective layer is formed on the surface of the sample, which improves the water resistance, room temperature emission intensity, and luminescent thermal stability of the coated sample. Finally, the improvement mechanism of the above multiple enhancements on luminescent properties is discussed and proposed. The above multiple enhancement effects make the sample have broad application for blue light-based warm and high-power WLEDs (white light-emitting diodes).

High quality germanate phosphor La(2-x-y)Ge2O7: Tb3+, Eu3+for WLED applications

White light emitting diodes (WLEDs), as the fourth generation of new light source, has the advantages of light weight, small size, low energy consumption, fast response speed and convenient use, but their poor thermal stability, high correlation color temperature (CCT) and low color rendering (Ra) limit their large-scale application of high-power WLED. In this work, we report the preparation of WLEDs by combining rare earth ions Tb3+-Eu3+ with La2Ge2O7, which exhibits tunable photoluminescence properties and excellent thermal stability. The detailed study shows that the layered structure of the material is conducive to efficient energy transfer (ET) between Tb3+ (sensitizer) and Eu3+ (activator), and effectively inhibits the luminescence attenuation caused by concentration quenching. Based on this, the doping ratio of Tb3+/Eu3+ in the phosphor is controlled and the phosphor is combined with blue chip to obtain excellent white light (CCT = 3955 K). The light efficiency (87 lm w−1) is comparable to that of commercial phosphors, and there is no significant decrease after continuous operation for 1000 h, which provides a good candidate material for the preparation of high-power WLED.

Luminescence-Tunable High-Power White Light-Emitting Diodes Through Dam-Adjusted Ceramic Substrate

In this work, luminescence-tunable high-power white light-emitting diodes (WLEDs) were fabricated by printing phosphor-in-silicone on 3-D ceramic substrates with adjusted dam structure. The 3-D ceramic substrate was prepared by a simple and efficient magnetic field-oriented grouting method in which silicate ceramic dam with adjusted height and angle was reliably bonded on a planar direct plating ceramic (DPC) substrate. The phosphor concentration of WLEDs was optimized to realize white light. At the phosphor concentration of 12 wt%, the packaged WLEDs achieve cool white light and high optical consistency. The influence of dam height and angle on the optothermal performances of WLEDs was investigated. As the dam height increases from 0.5 to 1.0 mm, the luminous efficiency (LE) of WLEDs first increases and then decreases, and the correlated color temperature (CCT) gradually decreases. At the dam height of 0.7 mm, the WLED achieves a high LE of 122 lm/W and a suitable CCT of 5008 K. Furthermore, the LE increases from 122 to 132 lm/W and the CCT decreases from 5006 to 4458 K when the dam angle changes from 0° to 40°. Importantly, the dam height and angle have no obvious influence on the surface temperature of WLEDs, and the WLEDs still display a low surface temperature even at high input current due to the effective heat dissipation of dam structure. The results indicate that the fabricated WLEDs achieve the tunable luminescence and low working temperature, which can be treated as an efficient and reliable high-power white source.

Structural Optimization of Vertically-Stacked White LEDs with a Yellow Phosphor Plate and a Red Quantum-Dot Film.

A remote-type white light-emitting diode (LED) consisting of a red quantum-dot (QD) film and a yellow phosphor plate was studied by both experiment and optical simulation. The sequence of the two color-conversion films had a substantial effect on the color-rendering properties of the vertically-stacked white LED, and the optimized configuration exhibited a high color rendering index of more than 90 thanks to the enhanced red component via the QD film. For the design of high-power white LED devices of a remote type, it was necessary to locate the color-conversion films below the diffuser plate to remove the substantial color dispersion depending on the viewing angle. The present study shows that high power and high color-rendering white LED devices can be realized in terms of two vertically-stacked color-conversion materials, which would provide long-term stability due to the remote design.

A Novel Preparation of Special-Shaped Phosphors-in-Glass by Gel Casting with Isobam for High-Power WLEDs Lighting.

Phosphors-in-glass (PiGs) regarded as a promising phosphor-converter for white light emitting diodes (WLEDs) is being researched widely. However, there are few reports on the effect of changing the shape of PiGs on the color rendering index (CRI) and heat dissipation of WLEDs. In this paper, gel casting with Isobam was first attempted in preparing special-shaped PiGs successfully. It exhibited that 76 wt.% was the optimum solid content based on the rheological properties of slurry and the shrinkage of green bodies. The sintering rate should be kept at a low speed and glass transition temperature (Tg) of glass powders must be higher than sublimation temperatures (Ts) of APS and Isobam. The CRI of PiGs was increased by about 27% after changing the shape of PiGs from cylinder to dome. Most importantly, operating temperature also reduced effectively the increase of the surface area of PiGs. Therefore, changing the shape of PiGs by gel casting with Isobam is a creative way for high-power WLEDs lighting.

Quantum efficiency of europium doped LaPO4 phosphors for UV sensing applications

The radiation conversion phenomenon is used for UV sensing applications with rare earth doped phosphors. This paper presents the results of structural and optical measurements of undoped and europium doped LaPO4 phosphors. LaPO4 phosphors with 1% mol, 2% mol, and 5% mol of europium were fabricated by the co-precipitation method. The effect of Eu3+ concentrations on the luminescence characteristics under UV LED excitation was investigated. The maximum quantum efficiency of luminescence (c.a. 82%) was obtained in sampled doped with 5% of europium. Full Text: PDF ReferencesM. Runowski, "Nanotechnologia – nanomateriały, nanocząstki i wielofunkcyjne nanostruktury typu rdzeń/powłoka", Chemik 68, 9, 766-775 (2014). DirectLink J. Zhou, J.L. Leano Jr., Z. Liu, D. Jin, K.-L. Wong, R.S. Liu, et al., "Impact of Lanthanide Nanomaterials on Photonic Devices and Smart Applications", Small 14, 1801882 (2018). CrossRef Z. Li, Y. Zhang, G. Han, "Lanthanide-Doped Upconversion Nanoparticles for Imaging-Guided Drug Delivery and Therapy", Springer Series in Biomater. Sci. Eng. 6, 139-164, (2016). CrossRef M. Lin, Y. Zhao, S. Wang, M. Liu, Z. Duan, Y. Chen, et al., "Recent advances in synthesis and surface modification of lanthanide-doped upconversion nanoparticles for biomedical applications", Biotechnol. Adv. 30, 1551-1561 (2012). CrossRef H. Su, Y. Nie, H. Yang, D. Tang, K. Chen, T. Zhang, "Improving the thermal stability of phosphor in a white light-emitting diode (LED) by glass-ceramics: Effect of Al2O3 dopant", J. Eur. Ceram. Soc. 38, 2005-2009 (2018). CrossRef J. Huang, X. Hu, J. Shen, D. Wu, C. Yin, R. Xiang, et al., "Facile synthesis of a thermally stable Ce3+:Y3Al5O12 phosphor-in-glass for white LEDs", Cryst. Eng. Comm 17, 7079-7085 (2015). CrossRef R. Zhang, H. Lin, Y. Yu, D. Chen, J. Xu, Y. Wang, "A new-generation color converter for high-power white LED: transparent Ce3+:YAG phosphor-in-glass", Laser Photon. Rev. 8, 158-164 (2014). CrossRef B. Zheng, Y. Bai, H. Chen, H. Pan, W. Ji, X. Gong, et al., "Near-Infrared Light-Excited Upconverting Persistent Nanophosphors in Vivo for Imaging-Guided Cell Therapy", ACS Appl. Mater. Interfaces 10, 19514 (2018). CrossRef J. Qiao, G. Zhou, Y. Zhou, Q. Zhang, Z. Xia, "Divalent europium-doped near-infrared-emitting phosphor for light-emitting diodes", Nature Communications 10 (1), 5267 (2019). CrossRef V. Singh, A. Kumar, C. Mehare, H. Jeong, S. Dhoble, "UV/VUV excited photoluminescence of Tb3+ doped LaPO4 green emitting phosphors for PDP applications", Optik 206, 163733 (2020). CrossRef G. Han, Y. Wang, C. Wu, J. Zhang, "Hydrothermal synthesis and vacuum ultraviolet-excited luminescence properties of novel Dy3+-doped LaPO4 white light phosphors", Mat. Res. Bull. 44 (12), 2255-2257 (2009). CrossRef K. S. Gupta, P. S. Ghosh, M. Sahu, K. Bhattacharyya, R. Tewari, V. Natarajan, "Intense red emitting monoclinic LaPO4:Eu3+ nanoparticles: host–dopant energy transfer dynamics and photoluminescence properties", RSC Adv. 5, 58832-58842 (2015). CrossRef

Highly efficient Ce: Lu(Mg,Al)2(Si,Al)3O12 phosphor ceramics for high-power white LEDs/LDs.

Lu3Al5O12: Ce3+ (LuAG: Ce3+) phosphor ceramics (PCs) with high quantum efficiency and excellent thermal stability are incredibly promising color converters for high-power white light emitting diodes (LEDs)/ laser diodes (LDs) lighting. However, the greenish emission of LuAG:Ce3+ PCs does not allow to reach white light emission upon pumping by a blue LED/ LD without an additional red luminescent material. In this work, a series of (Ce0.003Lu0.997)3(MgxAl1-2xSix)5O12 (LCMASG) (x = 0-0.15) PCs were fabricated by solid state reaction method. Impressively, the as-prepared PCs exhibited a distinct red-shift (513→538nm) and a 17% increase of the color index (CRI) of high-power white LED(58.4→70.4). Particularly, Ce: Lu(Mg, Al)2(Si, Al)3O12 PC with 15 at.% substitution concentration showed only 8% luminescent intensity loss at 150 °C and high internal quantum efficiency (IQE) of 82%, exhibiting desirable optical thermal stability. By combining with a 460 nm blue chip or a 455 nm laser source, white LED/LD devices based on the LCMASG PCs in a remote excitation mode were constructed. The optimized luminous efficiency of Ce: Lu(Mg, Al)2(Si, Al)3O12 PC with 15 at.% Mg2+/Si4+ doping up to 176.4 lm/W was obtained as the power density of the blue laser increased to 6.52 W/mm2. Also, a 4053K CCT of the warm white light emission was realized. Therefore, this work proves that the LCMASG PCs are promising to serve as color converters for high power LEDs/LDs lighting in the future.

Metal Inorganic–Organic Complex Glass and Fiber for Photonic Applications

The vitrification of hybrid materials (e.g., metal–organic frameworks and coordination polymers) is considered as the fourth generation of glass. To extend the hybrid glass family with photonic functionalities, we report a crystalline metal inorganic–organic complex (MIOC) (i.e., ZnCl2(HbIm)2, HbIm = benzimidazole) with a one-dimensional hydrogen bonded chain that can be melted to a stable liquid at elevated temperatures and subsequently quenched to form a large-sized bulk glass under ambient atmosphere with excellent thermal and chemical stability. Benefiting from the moderate glass-forming ability of the MIOC, we succeeded in the fabrication of the first MIOC glass fibers with diameters of 7–200 μm. The doping of the MIOC fibers by organic dyes results in anisotropic photoluminescence. Furthermore, the as-prepared MIOC bulk glass can be employed as the stable and inert host for inorganic phosphors, which leads to the development of a novel phosphor-in-MIOC glass composite and enables the fabrication of high-power white light-emitting diodes. Our findings make the ZnCl2(HbIm)2-based MIOC glass a promising material for photonic applications.

An effective heat dissipation strategy improving efficiency and thermal stability of phosphor-in-glass for high-power WLEDs

Phosphor-in-glass (PiG) is one of the most important spectral converters to overcome thermal effect in high-power white light-emitting diodes (LEDs). The Al2O3–SiO2–B2O3–ZnO–Na2O–Li2O glass was designed and sintered with Y3Al5O12:Ce3+ (YAG: Ce) phosphors at the low temperature of 650 °C to obtain YAG: Ce-PiG. The optimized YAG: Ce-PiG shows the white light of the luminous efficiency (LE), correlated color temperature (CCT) and chromaticity coordinate (CIE) of 177.5 lm/W, 6410 K and (0.31,0.34), respectively. The white LEDs (WLED) were fabricated by coupling the YAG: Ce-PiG with a blue light emitting chip, and the correlation between the luminescence properties, the thickness of PiG and the ratio of phosphors was investigated. More importantly, the WLEDs of a maximum luminous efficiency can reach up to 199.5 lm/W with the thickness of 0.35 mm. In addition, a structure with vacuum packaging technique based on the WLEDs lighting combined with sapphire as substrate was fabricated, which can effectively reduce the heat accumulation during the working process of WLEDs. Compared with normal non-vacuum packaging, the working temperature of WLEDs was reduced by about 35%, from 359.2 to 232.2 °C, with the novel vacuum packaging technique under 30W high-power chip and the luminous performance can still be maintained at 94.7%. In a word, the prepared YAG: Ce-PiG exhibits a great potential for application in high-power solid-state WLEDs.