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Size and Composition Dependent Multiple Exciton Generation Efficiency in PbS, PbSe, and PbS sub(x)Se sub(1-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

Nano letters, 2013-07, Vol.13 (7), p.3078-3085-3078-3085 [Periódico revisado por pares]

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  • Título:
    Size and Composition Dependent Multiple Exciton Generation Efficiency in PbS, PbSe, and PbS sub(x)Se sub(1-x) Alloyed Quantum Dots
  • Autor: Midgett, Aaron G ; Luther, Joseph M ; Stewart, John T ; Smith, Danielle K ; Padilha, Lazaro A ; Klimov, Victor I ; Nozik, Arthur J ; Beard, Matthew C
  • Assuntos: Confinement ; Coulomb friction ; Equivalence ; Excitation ; Excitation spectra ; Nanostructure ; Quantum confinement ; Quantum dots
  • É parte de: Nano letters, 2013-07, Vol.13 (7), p.3078-3085-3078-3085
  • Notas: ObjectType-Article-1
    SourceType-Scholarly Journals-1
    content type line 23
    ObjectType-Feature-2
  • Descrição: 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 PbS sub(x)Se sub(1-x) alloy for various QD diameters with corresponding bandgaps (E sub(g)) ranging from 0.6 to 1 eV. For each QD sample, we determine the MEG efficiency, eta sub(MEG), defined in terms of the electron-hole pair creation energy ( epsilon sub(eh)) such that eta sub(MEG) = E sub(g)/ epsilon sub(eh). In previous reports, we found that eta sub(MEG) 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 PbS sub(x)Se sub(1-x) alloyed QDs that eta sub(MEG) 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 PbS sub(x)Se sub(1-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.
  • Idioma: Inglês
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  • Realização: ABCD-USP USP   Logos de Redes Sociais: Freepik

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