Transparent Functionalized Zinc Oxide/Epoxy Nanocomposite with High Thermal Performance for High-Power Light-Emitting Diodes

A series of environmentally friendly agents were adopted to functionalize ZnO nanoparticles under moderate conditions. The functionalized ZnO was used as filler of epoxy resin to prepare transparent die attach material. The results show that functionalizations with citric acid and D-gluconic acid greatly improve the dispersion of ZnO in epoxy due to their high chelating capacities with ZnO and good compatibilities with epoxy. The transmittance of nanocomposite for 450 nm visible-light was increased by 27% from 81% to 93% after functionalization with citric acid. The thermal conductivity of 0.2 wt.% citric acid-functionalized ZnO/epoxy nanocomposite is 1.3 times of that of 0.2 wt.% as-synthesized ZnO/epoxy nanocomposite.