Crystal symmetry breaking and vacancies in colloidal lead chalcogenide quantum dots

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  • Federica Bertolotti, Dipartimento di Scienza e Alta Tecnologia and To.Sca.Lab, University of Insubria
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  • Dmitry N. Dirin, Eidgenossische Technische Hochschule Zurich, EMPA
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  • Maria Ibáñez, Eidgenossische Technische Hochschule Zurich, EMPA
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  • Frank Krumeich, Eidgenossische Technische Hochschule Zurich
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  • Antonio Cervellino, Paul Scherrer Institut
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  • Ruggero Frison, Physik-Institut, Universitat Zürich-Irchel, Istituto di Cristallografia
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  • Oleksandr Voznyy, University of Toronto
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  • Edward H. Sargent, University of Toronto
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  • Maksym V. Kovalenko, Eidgenossische Technische Hochschule Zurich, EMPA
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  • Antonietta Guagliardi, Istituto di Cristallografia
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  • Norberto Masciocchi, University of Insubria

Size and shape tunability and low-cost solution processability make colloidal lead chalcogenide quantum dots (QDs) an emerging class of building blocks for innovative photovoltaic, thermoelectric and optoelectronic devices. Lead chalcogenide QDs are known to crystallize in the rock-salt structure, although with very different atomic order and stoichiometry in the core and surface regions; however, there exists no convincing prior identification of how extreme downsizing and surface-induced ligand effects influence structural distortion. Using forefront X-ray scattering techniques and density functional theory calculations, here we have identified that, at sizes below 8 nm, PbS and PbSe QDs undergo a lattice distortion with displacement of the Pb sublattice, driven by ligand-induced tensile strain. The resulting permanent electric dipoles may have implications on the oriented attachment of these QDs. Evidence is found for a Pb-deficient core and, in the as-synthesized QDs, for a rhombic dodecahedral shape with nonpolar {110} facets. On varying the nature of the surface ligands, differences in lattice strains are found.

Original languageEnglish
JournalNature Materials
Pages (from-to)987-994
Number of pages8
Publication statusPublished - 1 Sep 2016

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