Enhanced light extraction of single-surface textured YAG:Ce transparent ceramics for high power white LEDs

摘要

Planar YAG:Ce transparent ceramics have great potential in the high power white LEDs due to the superior optical property and thermal conductivity. However, it is still a challenging issue to explore a simple method to enhance the forward light extraction of device. In this paper, the high quality YAG:Ce ceramics were fabricated by tape casting plus vacuum sintering, and the different surface textures, thicknesses of YAG:Ce ceramics and their assembly modes with high power LED chips were designed to enhance the light extraction. A fully dense and pore free microstructure with uniform grain size of 5.40 mu m was obtained, and the convex and concave impressions formed the texture and resulted in the photoluminescent enhancement of near six times in the single polished sample. The enhanced "light trapping effect" and reduced "TIR effect" worked together to enhance the forward light extraction of 22.5% in the SP-Up mode assembled device. The color coordinates of (0.3393, 0.3512) that close to white light were observed at the thickness of 0.6 mm. The high efficacy of similar to 93.0 lm/W and low CCT of 4144 K could be obtained at the thickness of 0.8 mm in the simple remote mode. YAG:Ce planar transparent ceramics with special surface texture and assembly mode provided in this study greatly enhanced the extractions efficacy and improved the emission color, and then promoted their industrial application in high power white LEDs.