Crystal symmetry breaking and vacancies in colloidal lead chalcogenide quantum dots.
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.
Dipartimento di Scienza e Alta Tecnologia and To.Sca.Lab, Università dell'Insubria, via Valleggio 11, I-22100 Como, Italy.
Federica
F
Bertolotti
Department of Chemistry and Applied Biosciences, ETH, Vladimir-Prelog-Weg 1, CH-8093 Zürich, Switzerland.|Empa-Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, CH-8600 Dübendorf, Switzerland.
Dmitry N
0000-0002-5187-4555
DN
Dirin
Department of Chemistry and Applied Biosciences, ETH, Vladimir-Prelog-Weg 1, CH-8093 Zürich, Switzerland.|Empa-Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, CH-8600 Dübendorf, Switzerland.
Maria
M
Ibáñez
Department of Chemistry and Applied Biosciences, ETH, Vladimir-Prelog-Weg 1, CH-8093 Zürich, Switzerland.
Frank
F
Krumeich
SLS, Laboratory for Synchrotron Radiation-Condensed Matter, Paul Scherrer Institut, CH-5232 Villigen, Switzerland.
Antonio
A
Cervellino
Department of Chemistry, University of Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland.|Istituto di Cristallografia and To.Sca.Lab, CNR, via Valleggio 11, I-22100 Como, Italy.
Ruggero
R
Frison
The Edward S. Rogers Department of Electrical and Computer Engineering, University of Toronto, 10 King's College Road, Toronto, Ontario M5S 3G4, Canada.
Oleksandr
0000-0002-8656-5074
O
Voznyy
The Edward S. Rogers Department of Electrical and Computer Engineering, University of Toronto, 10 King's College Road, Toronto, Ontario M5S 3G4, Canada.
Edward H
EH
Sargent
Department of Chemistry and Applied Biosciences, ETH, Vladimir-Prelog-Weg 1, CH-8093 Zürich, Switzerland.|Empa-Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, CH-8600 Dübendorf, Switzerland.
Maksym V
0000-0002-6396-8938
MV
Kovalenko
Istituto di Cristallografia and To.Sca.Lab, CNR, via Valleggio 11, I-22100 Como, Italy.
Antonietta
A
Guagliardi
Dipartimento di Scienza e Alta Tecnologia and To.Sca.Lab, Università dell'Insubria, via Valleggio 11, I-22100 Como, Italy.
Norberto
0000-0001-9921-2350
N
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