Samsung Advanced Institute of Technology

Understanding the precise effects of defects on the photophysical properties of quantum dots (QDs) is essential to the development of QDs with near-unity luminescence. Due to the complicated nature of defects in QDs, their origins and detailed roles still remain rarely understood. In this regard, using ultrafast optical spectroscopies with detailed chemical analysis, we investigated the effect of surface defects on the optical properties of InP/ZnSe/ZnS QDs by introducing shell defects through controlled trifluoroacetic acid (TFA) etching. The TFA treatment on InP/ZnSe/ZnS QDs removed the ZnS shell partially as well as ligands, and reduced the quantum yield by generating surface traps which is energetically deep. InP/ZnSe/ZnS QDs with those traps show two distinctive exciton trapping dynamics; one is Auger recombination occurring on hundreds picosecond and the other is sub 10 ps fast trapping. Especially, Auger recombination dynamics seems to coincide with the removal of Z-type zinc-oleate ligands which lead to S-dandling bond on the surface. Based on these results, we propose the possible trap-assisted non-radiative decay pathways between band-edge state and deep traps in InP/ZnSe/ZnS QDs.