Colloidal semiconductor nanocrystals have attracted much interest due to their unique optical properties, with applications ranging from displays to biomedical imaging. Nanocrystal optical properties depend on the structure of the surface, where defects can lead to traps. CdSe nanocrystals undergo surface reorganization, or self-healing, to eliminate defects, removing midgap traps from the band structure. However, the effect of this process on the optical spectrum is not well studied. Here, we show that self-healing not only eliminates midgap traps from the band structure but also brightens the spectrum and causes the excitonic states to emerge as the dominant features, in agreement with experimental annealing studies. We find that self-healing can lead to new traps like bonded Se-Se or Cd-Cd dimers, and their behavior is different from that of undercoordinated atom traps. These results suggest that eliminating traps requires a balance of allowing enough surface reorganization to eliminate undercoordinated atoms, but not so much that dimeric traps form.
|Number of pages||8|
|Journal||Journal of Physical Chemistry Letters|
|State||Published - 9 Feb 2023|
Bibliographical noteFunding Information:
This work was supported by the Department of Energy under Grant DMR-1905164. This work used the Extreme Science and Engineering Discovery Environment (XSEDE) resource Comet at the San Diego Supercomputing Center through allocation TG-DMR190054, which is supported by National Science Foundation Grant ACI-1548562. T.G. received financial support from the Technion-MIT fellowship and the Technion-New England Foundation. A.R.M. was supported by the National Science Foundation Graduate Research Fellowship under Grant 1122374.
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