Coverage-mediated suppression of blinking in solid state quantum dot conjugated organic composite nanostructures

Size-correlated single-molecule fluorescence measurements on CdSe quantum dots functionalized with oligo( phenylene vinylene) (OPV) ligands exhibit modified fluorescence intermittency ( blinking) statistics that are highly sensitive to the degree of ligand coverage on the quantum dot surface. As evidenced by a distinct surface height signature, fully covered CdSe-OPV nanostructures ( similar to 25 ligands) show complete suppression of blinking in the solid state on an integration time scale of 1 s. Some access to dark states is observed on finer time scales ( 100 ms) with average persistence times significantly shorter than those from ZnS-capped CdSe quantum dots. This effect is interpreted as resulting from charge transport from photoexcited OPV into vacant trap sites on the quantum dot surface. These results suggest exciting new applications of composite quantum dot/organic systems in optoelectronic systems.