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, Al
₂
O
₃
nanoparticles (NPs) are doped into silicone. Different compositions of Al
₂
O
₃
NPs are used and the optimal composition is found to be 0.3%. Compared with LEDs packaged by UV curing without Al
₂
O
₃
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 Al
₂
O
₃
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.