Improved Light Extraction of Nitride-Based Light-Emitting Diodes by Al2O3-Doped UV-Curing Encapsulant

Silicone-based UV curing has recently been developed as a novel kind of encapsulation technology, which is time-saving and cost-effective for the package of light-emitting diodes (LEDs). In this work, to improve the light output power (LOP) and device reliability of LEDs packaged by UV curing, Al2O3 nanoparticles (NPs) are doped into silicone. Different compositions of Al2O3 NPs are used and the optimal composition is found to be 0.3%. Compared with LEDs packaged by UV curing without Al2O3 doping (256.3 mW) and by traditional thermal-curing (264.1 mW) encapsulants, the LOP is increased to 272.9 mW for LED with Al2O3-NP-doped encapsulant. The enhancement of LOP is attributed to both the increased refractive index and light scattering effect of the Al2O3 NPs, which improves the light extraction efficiency (LEE) of the encapsulant. Furthermore, the improvement of LEE also suppresses the heat generation and thus improving the long-term reliability of the devices. These results indicate that using high refractive index materials as doping, UV curing could be an excellent choice as a novel package technology for the LED industry.