Tunable Polymer Nanocomposites for Advanced LED Lighting Systems
Researchers from Rensselaer Polytechnic Institute working with the Lighting Enabled Systems & Applications ERC (LESA), funded by the National Science Foundation, have developed a new approach for the design and synthesis of improved silicone nanocomposites with tunable optical properties needed to design and manufacture ultra-efficient LED lighting systems. This discovery was featured as the January 2013 cover story of Langmuir.
Today’s LED lighting systems are made from optical materials that have a very narrow range of refractive index (RI) values, limiting both the color quality and efficiency of white LEDs. With tunable RI optical materials used to move light from the semiconductor chip to the outside world, the overall performance, reliability, and efficiency of LED lighting systems and optical designs is significantly improved.
Refractive index (RI) governs the interaction between optical materials and light. For best efficiency, very high RI polymers – made with a high volume-percent loading of specially designed nanoparticles – are needed. But when nanoparticle loading gets too high, agglomeration (or clumping) typically occurs and creates a loss of transparency that limits the range of RI control available.
Conventional chemical tricks to prevent clumping use specialized organic molecules (ligands) to help dissolve the nanoparticles in the polymer at the surface, thereby keeping the particles apart. However, these approaches also don’t work well at high loading. To prevent this problem and create high RI polymers with good optical performance, processes for fabricating more complex molecular structures on the nanoparticle surfaces are needed.