Uncovering Hot Hole Dynamics in CdSe Nanocrystals.
Single and multiple exciton relaxation dynamics of CdSe/CdZnS nanocrystal quantum dots (QDs) monitored at the two lowest optical transitions, 1Se-1S3/2 and 1Se-2S3/2, have been examined using ultrafast transient absorption (TA) spectroscopy. For the CdSe/CdZnS QDs studied, the 1Se-1S3/2 and 1Se-2S3/2 transitions are widely separated (∼180 meV) compared to bare CdSe QDs (∼50-100 meV), allowing for clearly distinguishable TA signals attributable to hot hole relaxation. Holes depopulate from the 2S3/2 state with a lifetime of 7 ± 2 ps, which is consistent with the predictions for hole relaxation via a phonon coupling pathway to lower-energy hole states, with possible contributions from hole trapping as well. These results suggest that tuning the surface chemistry of semiconductor QDs is a viable route to measure and possibly control their hot hole relaxation dynamics.
§Rochester Advanced Materials Program, †Department of Chemistry, and #The Institute of Optics, University of Rochester, Rochester, New York 14627, United States.
Cunming
C
Liu
§Rochester Advanced Materials Program, †Department of Chemistry, and #The Institute of Optics, University of Rochester, Rochester, New York 14627, United States.
Jeffrey J
JJ
Peterson
§Rochester Advanced Materials Program, †Department of Chemistry, and #The Institute of Optics, University of Rochester, Rochester, New York 14627, United States.
Todd D
TD
Krauss
Auger process; Poisson population; biexciton; hot hole relaxation; transient absorption