Polymeric Materials in Phosphor-Converted LEDs for Lighting Applications: Outlook and Challenges

Solid-state lighting technologies such as LED-based lighting are steadily gaining market share and promise significant energy efficiencies. This article describes some key polymer materials used in LED packages, especially for phosphor encapsulation. We discuss the use of various silicone materials as encapsulants, and bring out the advantages and issues with this approach. The key issues discussed include thermal stability, the consequences of exposure to high temperatures such as discoloration and mechanical failure, refractive index matching, and heat removal (thermal conductivity). We present a number of approaches designed to alleviate these issues, including the use of composite/hybrid materials.