Measurement of Energy Transfer Time in Colloidal Mn-Doped Semiconductor Nanocrystals

The exciton-dopant energy transfer time in colloidal Mn-doped CdS/ZnS core/shell nanocrystals was investigated via pump-probe transient absorption measurements. The energy transfer time was obtained from the comparative analysis of the dynamics of exciton relaxation ill undoped and doped nanocrystal samples with well-defined doping radius and concentration. For this purpose, file transient absorption was measured in the near-IR region probing primarily intraband transition of excitons Without signal saturation even at high exciton densities, which is Particularly useful for Studying the energy transfer in a wide range of exciton densities. With,in increasing Mn doping concentration, exciton-dopant energy transfer became faster, effectively competing with both radiative and nonradiative relaxation of exciton. In the spherical Mn-doped CdS/ZnS core/shell nanocrystals Studied here, the time scale of energy transfer between a single pair of exciton and Mn2+ ion was determined to be similar to 60 ps.