Photo-stable cross-linked micron bead with functionalized quantum via suspension polymerization for color conversion

Acrylate groups were introduced on quantum dots (QD) via ligand exchange followed by nucleophilic reaction. The QDs were then polymerized with other multi-functional acrylic monomers in this study. Two acrylate groups were introduced at the end of an elongated ligand and the ligands with two acrylate groups were fully coordinated on the entire surface of the QD. This ligand modification scheme made the QDs highly reactive and also compatible with common organic solvents. No decrease in the quantum yield of the QDs was observed after ligand modification and the adduction reaction. The acrylate functional groups in the QDs were verified by 1H NMR and FT-IR. The prepared QDs with a terminal acrylate group were reacted with trimethylolpropane triacrylate and 1,6-hexanediol diacrylate to form micrometer scale beads via suspension polymerization. The diameter of the spherical beads was in the range of 80–150 μm and QDs 13 nm in diameter were found to be evenly dispersed in the polymer beads. The QD-polymer beads were applied to color conversion layers (CCL) on a blue light emitting diode (LED). The QD-polymer beads showed a 50% reduction over 72 h from the initial optical efficiency, while the QD embedded in the PMMA matrix (QD-PMMA) was reduced by 50% for 14 h.