Controlling the Surface Properties of TiO2 for Improvement of the Photo-performance and Color Uniformity of the Light-emitting Diode Devices

Abstract

The photo-performance and color uniformity of the light-emitting diodes (LEDs) were enhanced by controlling the surface properties of the titanium dioxide (TiO2) particles as light scatting materials using a sol-gel-based surface modification method. Silane coupling agents of different carbon chain lengths (C3–C16) were introduced onto the TiO2 surface for investigating the light scattering effect depending on the TiO2 dispersibility in the encapsulant. The dispersibility of the modified TiO2 particles was greater than that of the as-prepared TiO2 particles (1.6–2.5 times). The dispersibility of TiO2 improved with the increasing carbon chain length of silane (C3–C6). However, the dispersibility did not increase but reduced when the carbon chain length was considerably long (C16) because the TiO2 surface was more hydrophobic than the encapsulant. After the fabrication of the LED devices, the TiO2-loaded LED device showed high photometric flux and low correlated color temperature despite using the same concentration of phosphor (3.0wt.% with respect to the added silicone resin). Furthermore, the photo-performance and color uniformity improved when the TiO2 dispersibility was increased. This can be attributed to the enhancement of light scattering in the LED package when the interfacial affinity of the TiO2/encapsulant was improved.