Unique composite architecture of phosphor-in-glass film coated on different heat-conducting substrates for high-brightness laser lighting

Laser lighting is considered as a next-generation high-brightness semiconductor light source, and the laser-excited phosphor (LEP) technology is the common method to produce laser-driven white lighting. Considering the high energy density of laser excitation, some inorganic color converters have been developed to replace the traditional phosphor-in-resin, including single crystal (SC), phosphor ceramics (PC), and phosphor-in-glass (PiG). The PiG converter displays some competitive advantages of adjustable luminescence, simple process, and low cost. Unfortunately, the PiG bulk is confronted with seriously luminescence saturation even under low laser power density (LPD) owing to its low thermal conductivity (TC) of glass matrix. Recently, a thin film converter of PiG film (PiGF) sintered on heat-conducting substrate (PiGF@HCS) have been developed to replace the PiG bulk. The PiGF@HCS not only maintains the outstanding merits of PiG, but also bears the laser irradiation with high LPD originating from its efficient heat dissipation from the high TC of substrates. Although many PiGF@HCS converters have been developed for transmissive or reflective laser lighting, the overall comparison of optical-thermal performances of these PiGF@HCS converters has not been studied in laser lighting so far. Furthermore, different heat-conducting substrates have strong effect on the heat transfer and light transport in the PiGF@HCS, which further affects luminescence saturation and phosphor conversion efficiency.

Recently, a team of material scientists led by Yang Peng from Huazhong University of Science and Technology, China first reported the synthesis, microstructure, and optical-thermal performances of PiGF@HCSs. This work not only comprehensive analyses the optical-thermal performances, reliability, and cost in PiGF@HCSs with different heat-conducting substrates, but also predicts that PiGF@HCSs can be used as a new type in high-brightness laser lighting.

The team published their work in Journal of Advanced Ceramics on January 3, 2025.

“In this report, we synthesized PiGF@HCSs of PiGF@sapphire, PiGF@Al₂O₃, PiGF@AlN, and PiGF@BN-AlN by a simple film printing and low-temperature sintering technology. The PiGFs are tightly sintered on the surface of sapphire, Al₂O₃, AlN, and BN-AlN, and no obvious crack and delamination are observed, which is prone to realize higher bonding strength and low interfacial thermal resistance. Using SEM techniques, the phosphor particles are embedded in the glass matrix of PiGF@HCSs with clear phosphor-glass boundary,” said Yang Peng, associate professor at Institute of Aeronautics and Astronautics at Huazhong University of Science and Technology (China), a senior expert whose research interests focus on the field of electronic packaging.

“Although many PiGF@HCS converters have been developed for transmissive or reflective laser lighting, the overall comparison of optical-thermal performances of these PiGF@HCS converters has not been studied in laser lighting so far. Furthermore, different heat-conducting substrates have strong effect on the heat transfer and light transport in the PiGF@HCS, which further affects luminescence saturation and phosphor conversion efficiency. In this case, these PiGF@HCS converters cannot reach a balance point in performances, reliability, and cost, limiting their actual applications in high-brightness laser lighting.” said Yang Peng.

“The PiGF@BN-AlN enables a maximum LF of 3058 lm@21 W/mm² owing to the enhanced light extraction and phosphor conversion from the high reflectivity of BN-glass layer. Furthermore, the LE of PiGF@BN-AlN reaches up to 194 lm/W, which is 1.6 times that of PiGF@AlN, while that of PiGF@sapphire and PiGF@Al₂O₃ are 192 lm/W and 150 lm/W, respectively,” said Yang Peng.

The PiGF@sapphire, PiGF@Al₂O₃, PiGF@AlN, and PiGF@BN-AlN converters display stable working temperatures of 302℃, 298℃, 277℃, and 310℃, respectively, even after the laser driven time of 270 min. The LF maintenances of PiGF@sapphire, PiGF@Al₂O₃, PiGF@AlN, and PiGF@BN-AlN converters reach up to 95.3%, 93%, 94.6%, and 95%, respectively. “The results indicate that the fabricated PiGF@HCS converters achieve high luminescence stability even under their LPD-STs, making the promising converters for high-brightness laser lighting.” said Yang Peng.

However, more delicate research works are still needed to explore the suitability of PiGF@HCS converters as a new material. In this regard, Peng also put forward three major development directions may be pursued in future works including the simulation calculation, water vapor resistance, and thermal/structural stability of the PiGF during performance.

Other contributors include Xin Liu, Mingxiang Chen, Jiuzhou Zhao, Hongjin Zhang, Qing Wang. Xin Liu, Mingxiang Chen from the school of Mechanical Science and Engineering, Huazhong University of Science and Technology, China; Jiuzhou Zhao, Hongjin Zhang from the school of Aerospace Engineering, Huazhong University of Science and Technology, China; Qing Wang from the school of Energy and Power Engineering, Huazhong University of Science and Technology, China.

This work was supported by National Natural Science Foundation of China (52475594) and National Key Research and Development Program of China (2022YFB3604803). The authors would like to thank the Analytical and Testing Center of Huazhong University of Science and Technology for the support in PL, SEM, decay measurements.

About Author

Yang Peng (corresponding author), Associate professor, doctoral supervisor, Senior Member of IEEE, Senior member of Mechanical Engineering Society, core member of Advanced electronic Packaging materials and technology team. He is mainly engaged in advanced electronic packaging technology and application research, including aerospace electronic devices and microsystem integration, photoelectric devices and photothermal control, MEMS devices and reliability research work. In recent years, he directed the National Natural Science Foundation, the national key research and development plan sub-project, Hubei key research and development plan, East Lake High-tech Zone, postdoctoral science fund first-class funding, as a backbone to participate in the national key research and development plan, equipment pre-research fund key projects, "eye action" project. So far, he has published more than 70 papers in international first-class journals such as Adv. Mater., Adv. Fun. Mater., J. Adv. Ceram. He served as the editorial board member of the first Youth Echelon of the Journal of Luminescence, guest editor of the special issue of Micromachines and Advanced Technologies in Electronic Packaging, and reviewer of more than 30 journals.

Qing Wang (corresponding author) graduated from the School of Mechanical Science and Engineering, Huazhong University of Science and Technology in 2023, and then engaged in postdoctoral research in the School of Energy and Power Engineering, Huazhong University of Science and Technology. She is mainly engaged in the research of advanced electronic packaging technology, micro and nano manufacturing technology, packaging thermal management and application. In recent years, she directed in charge of the China Postdoctoral Science Fund, the State key laboratory open project, Hubei Province Natural Science fund projects. So far, she has published more than 22 papers as the first/corresponding author in international first-class journals such as Journal of Manufacturing Processes, Electrochimica Acta and Materials today communications. She served as a reviewer for Nano Materials Science, Journal of the Taiwan Institute of Chemical Engineers, Micromachines and other journals.

About Journal of Advanced Ceramics

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