Impact of Stoichiometry on the Electronic Structure of PbS Quantum Dots
Name
Kim-2013-Impact of stoichiometry on the electronic structure of PbS quantum dots.pdf
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Author(s)
Kim, Donghun
Kim, Dong-Ho
Lee, Joo-Hyoung
Grossman, Jeffrey C.
Date Issued
May 2013
Journal
Physical Review Letters
Publisher
American Physical Society
Citation
Kim, Donghun, Dong-Ho Kim, Joo-Hyoung Lee, and Jeffrey C. Grossman. Impact of Stoichiometry on the Electronic Structure of PbS Quantum Dots. Physical Review Letters 110, no. 19 (May 2013). © 2013 American Physical Society.
Version
Final published version
Abstract
Although the stoichiometry of bulk lead sulfide (PbS) is exactly 1∶1, that of quantum dots (QDs) can be considerably different from this crystalline limit. Employing first-principles calculations, we show that the impact of PbS QD stoichiometry on the electronic structure can be enormous, suggesting that control over the overall stoichiometry in the QD will play a critical role for improving the efficiency of optoelectronic devices made with PbS QDs. In particular, for bare PbS QDs, we find that: (i) stoichiometric PbS QDs are free from midgap states even without ligand passivation and independent of shape, (ii) off stoichiometry in PbS QDs introduces new states in the gap that are highly localized on certain surface atoms, and (iii) further deviations in stoichiometry lead to QDs with “metallic” behavior, with a dense number of energy states near the Fermi level. We further demonstrate that this framework holds for the case of passivated QDs by considering the attachment of ligand molecules as stoichiometry variations. Our calculations show that an optimal number of ligands makes the QD stoichiometric and heals unfavorable electronic structure, whereas too few or too many ligands cause effective off stoichiometry, resulting in QDs with defect states in the gap.
MIT Department
Massachusetts Institute of Technology. Department of Materials Science and Engineering
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DOI of Published Version
https://doi.org/10.1103/PhysRevLett.110.196802
