Highly transparent thermal stable silicone/titania hybrids with high refractive index for LED encapsulation

Silicone/titania hybrids for LED encapsulation were synthesized via hydrolysis and condensation reaction between tetrabutyl titanate and silica sol containing phenyl groups and long alkyl chains. Crack-free thick films (~1 mm) were fabricated by curtain painting. The hybrid films with different Ti contents were characterized by FTIR, UV–VIS, TGA/DSC, AFM, TEM, ellipsometer, etc. Results show that the hybrid films contain long alkyl chains which have high thermal stability against yellowing owing to the steric hindrance given by long alkyl chains. The hybrid films have high transmittance (≥98% in visible range) and high refractive index (1.591–1.681). In LED encapsulation, the silicone/titania hybrids with an RI of 1.605 increased the light extraction efficiency of bare blue LEDs by 19.4%.