Size and composition dependent multiple exciton generation efficiency in PbS, PbSe, and PbSxSe1-x alloyed quantum dots

Aaron G. Midgett, Joseph M. Luther, John T. Stewart, Danielle K. Smith, Lazaro A. Padilha, Victor I Klimov, Arthur J. Nozik, Matthew C. Beard

Research output: Contribution to journalArticle

93 Citations (Scopus)

Abstract

Using ultrafast transient absorption and time-resolved photoluminescence spectroscopies, we studied multiple exciton generation (MEG) in quantum dots (QDs) consisting of either PbSe, PbS, or a PbSxSe1-x alloy for various QD diameters with corresponding bandgaps (Eg) ranging from 0.6 to 1 eV. For each QD sample, we determine the MEG efficiency, ηMEG, defined in terms of the electron-hole pair creation energy (εeh) such that ηMEG = Eg/ εeh. In previous reports, we found that ηMEG is about two times greater in PbSe QDs compared to bulk PbSe, however, little could be said about the QD-size dependence of MEG. In this study, we find for both PbS and PbSxSe1-x alloyed QDs that ηMEG decreases lineally with increasing QD diameter within the strong confinement regime. When the QD radius is normalized by a material-dependent characteristic radius, defined as the radius at which the electron-hole Coulomb and confinement energies are equivalent, PbSe, PbS, and PbSxSe1-x exhibit similar MEG behaviors. Our results suggest that MEG increases with quantum confinement, and we discuss the interplay between a size-dependent MEG rate versus hot exciton cooling.

Original languageEnglish
Pages (from-to)3078-3085
Number of pages8
JournalNano Letters
Volume13
Issue number7
DOIs
Publication statusPublished - Jul 10 2013

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Quantum Dots
Excitons
Semiconductor quantum dots
quantum dots
excitons
Chemical analysis
radii
LDS 751
lead selenide
Electrons
Quantum confinement
Photoluminescence spectroscopy
Spectrum Analysis
Energy gap

Keywords

  • carrier multiplication
  • exciton dynamics
  • Multiple exciton generation
  • PbS quantum dots
  • quantum size effects
  • solar energy conversion

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Bioengineering
  • Chemistry(all)
  • Materials Science(all)
  • Mechanical Engineering
  • Medicine(all)

Cite this

Midgett, A. G., Luther, J. M., Stewart, J. T., Smith, D. K., Padilha, L. A., Klimov, V. I., ... Beard, M. C. (2013). Size and composition dependent multiple exciton generation efficiency in PbS, PbSe, and PbSxSe1-x alloyed quantum dots. Nano Letters, 13(7), 3078-3085. https://doi.org/10.1021/nl4009748

Size and composition dependent multiple exciton generation efficiency in PbS, PbSe, and PbSxSe1-x alloyed quantum dots. / Midgett, Aaron G.; Luther, Joseph M.; Stewart, John T.; Smith, Danielle K.; Padilha, Lazaro A.; Klimov, Victor I; Nozik, Arthur J.; Beard, Matthew C.

In: Nano Letters, Vol. 13, No. 7, 10.07.2013, p. 3078-3085.

Research output: Contribution to journalArticle

Midgett, AG, Luther, JM, Stewart, JT, Smith, DK, Padilha, LA, Klimov, VI, Nozik, AJ & Beard, MC 2013, 'Size and composition dependent multiple exciton generation efficiency in PbS, PbSe, and PbSxSe1-x alloyed quantum dots', Nano Letters, vol. 13, no. 7, pp. 3078-3085. https://doi.org/10.1021/nl4009748
Midgett, Aaron G. ; Luther, Joseph M. ; Stewart, John T. ; Smith, Danielle K. ; Padilha, Lazaro A. ; Klimov, Victor I ; Nozik, Arthur J. ; Beard, Matthew C. / Size and composition dependent multiple exciton generation efficiency in PbS, PbSe, and PbSxSe1-x alloyed quantum dots. In: Nano Letters. 2013 ; Vol. 13, No. 7. pp. 3078-3085.
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