Defect states and charge transport in quantum dot solids

ORAL

Abstract

Defects at the surface of semiconducting quantum dots (QD) give rise to electronic states within the gap, which are detrimental to charge transport properties of QD devices. We investigated charge transport in silicon quantum dots with deep and shallow defect levels, using ab initio calculations and constrained density functional theory.[1] We found that shallow defects may be more detrimental to charge transport than deep ones, with associated transfer rates differing by up to 5 orders of magnitude for the small dots (1-2 nm) considered here. Hence our results indicate that the common assumption that the ability of defects to trap charges is determined by their position in the energy gap of the QD, is too simplistic, and our findings call for a reassessment of the role played by shallow defects in QD devices. Overall, our results highlight the key importance of taking into account the atomistic structural properties of QD surfaces when investigating transport properties. [1] N. P. Brawand, Matthew B. Goldey, Marton Voros, and Giulia Galli, submitted

*Center for Hierarchical Materials Design, funded by National Institute of Standards and Technology 70NANB14H012; Center for Advanced Solar Photophysics, funded by the U.S. Department of Energy (DOE); and U.S. DOE, Contract No. DE-AC02-06CH11357

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Authors

  • Nicholas Brawand

    • Institute for Molecular Engineering, University of Chicago

  • Matthew Goldey

    • Institute for Molecular Engineering, University of Chicago

  • Marton Voros

    • Materials Science Division, Argonne Natl Lab
    • Argonne Natl. Lab
    • Argonne Natl Lab
    • Materials Science Division, Argonne National Laboratory

  • Giulia Galli

    • Univ of Chicago and Argonne National Laboratory
    • Univ of Chicago
    • University of Chicago; Argonne National Laboratory
    • Institute for Molecular Engineering, University of Chicago; Argonne National Laboratory
    • Institute for Molecular Engineering, University of Chicago and Materials Science Division, Argonne Natl Lab
    • Institute for Molecular Engineering, University of Chicago; Materials Science Division, Argonne National Laboratory
    • Institute for Molecular Engineering, University of Chicago, Chicago, IL 60637 and Materials Science Division, Argonne National Laboratory, Lemont, IL
    • Institute for Molecular Engineering, University of Chicago and Argonne Natl Lab
    • University of Chicago, Chicago, IL 60637, USA
    • The University of Chicago, Institute for Molecular Engineering and Argonne National Laboratory
    • Argonne National Laboratory and University of Chicago
    • Institute for Molecular Engineering, University of Chicago and Materials Science Division, Argonne National Laboratory
    • University of Chicago
    • The University of Chicago
    • University of Chicago and Argonne National Laboratory