Improvement of optical performances of LEDs by dual-layer structure of nano-TiO2 and phosphor

We presented a dual-layer packaging layout and its enhancement effect on light efficiency (LE) and angular color uniformity (ACU). In this packaging layout, a thin film of TiO₂/ silicone nanocomposite is inserted between LED chips and phosphor layers. And the phosphor layer is a convex shape and Restricted to the surface of LED chips. The effects of TiO₂ concentration and particle size on the LE and ACU performances were studied by the Monte Carlo ray-tracing optical simulation. Results show that the LE is improved up to 8.5%, and the angular color deviation is reduced from 1100 K to 180K. In nano-TiO₂ composite layer, high concentration can result in higher LE and ACU. And increasing particle size can reduce the ACU deviation. But when the particle size is beyond an optimized value, the LE is significantly decreased.