Taguchi method-assisted optimization of multiple effects on the optical and luminescence performance of Ce:YAG transparent ceramics for high power white LEDs†
Ce:YAG transparent ceramics have great potential in white LEDs, especially under high power packaging technology, due to their superior thermal performance. However, their interactions and the synergistic effects among multiple factors limit the in-depth understanding and higher efficiency conversion of these ceramics for popular applications, and the single variable research approach is incapable of addressing the complex and diverse requirements for luminescence performance in as-constructed LED devices. In this work, for the first time, orthogonal experiments were designed to comprehensively evaluate the composite effects of thickness, doping concentration and surface roughness on the luminous efficiency and ideal white light of a constructed device with the assistance of the Taguchi method and one-way variance analysis. High throughput fabrication of ceramics was achieved using the novel Isobam gel casting method plus vacuum sintering. The Ce3+ doping concentration was proved to be the most dominant of these factors for excellent luminescence performance. The optimized factors of ceramics for luminous efficiency were 1.5 mm thickness, 0.2 at% Ce3+ concentration and double-polishing of surface roughness, while the optimized factors for good CIE were 0.4 mm thickness, 0.05 at% Ce3+ concentration and double-polishing. Therefore, this work not only shows how the Taguchi method can achieve a better group of multiple factors, but also how the synergistic effects of these factors work together. They significantly affect the optical properties of Ce:YAG ceramics and their performance in high power LED applications. These results are crucial for advancing transparent ceramics applications.