In this study, we proposed a flexible method to realize a cylindrical tuber encapsulant layer. Firstly, patterned LED substrate with silicone-wetting and silicone-repellency surfaces was prepared by depositing low surface energy modified nanosilica particles. Secondly, coating phosphor gel onto the LED chip. Thirdly, coating the encapsulant (silicone OE6550A/B) onto the phosphor gel layer. The silicone stops spreading at the border of silicone-wetting and silicone-repellency surfaces and its final contact angle can be adjusted to any value between the contact angle of silicone-wetting and silicone-repellency surface, so it is very easy to realize dome-shape silicone layer with contact angle of ∼90°. For COB-LEDs with LED array in series, the final silicone layer geometry is similar to the cylindrical tuber. The results show that compared to the conventional flat encapsulant layer, the proposed encapsulant layer can improve the light efficiency by > 60% for pure blue light and 13.6% for white light at correlated color temperature (CCT) of ∼5500K.

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