Synthesis of end group functionalized PMMA ligands for QD based LSCs

Luminescent solar concentrators (LSCs) enhance the efficiency of photovoltaic devices (PVs) through the absorption and redirection of light by nanocrystal quantum dots in a polymer matrix.  Through an exchange of native ligands for selected polymer ligands, nanocrystal quantum dots (QDs) are coated in poly(methyl methacrylate) (PMMA) ligands of known length. Reversible Addition-Fragmentation chain Transfer (RAFT) radical polymerization can be used to selectively generate polymers of preferred molecular weight. Current molecular weight targets are 2,000, 3,000, 5,000, 10,000 Da and the isolated polymer is determined by GPC. This research is aimed at producing a finely tuned polymer matrix for use in luminescent solar concentrators to control the dispersity and aggregation of nanocrystal quantum dots. Hydroxy-, amine-, imidazole-, dithiocarbomate-, or thiol- terminated PMMA have been explored for optimal ligand exchange to decrease aggregation while minimizing quantum yield loss. Currently thiol capping of the PMMA is the desired end group for ligand exchange. Formation of a thiolactam ring during the capping process has been observed and can possibly be avoided through addition of a spacer via diblock copolymerization.