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Ligand-induced symmetry breaking, size and morphology in colloidal lead sulfide QDs: from classic to thiourea precursors

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  • Federica Bertolotti
  • ,
  • Andrew H. Proppe, University of Toronto, Canada
  • Dmitry N. Dirin, ETH, Schweiz
  • Mengxia Liu, University of Toronto, Canada
  • Oleksandr Voznyy, University of Toronto, Canada
  • Antonio Cervellino, Paul Scherrer Inst, Paul Scherrer Institute, Schweiz
  • Simon J.L. Billinge, Columbia University, USA
  • Maksym V. Kovalenko, ETH, Schweiz
  • Edward H. Sargent, University of Toronto, Canada
  • Norberto Masciocchi, University of Insubria, Italien
  • Antonietta Guagliardi , CNR, Istituto Di Cristallografia (IC-CNR), Consiglio Nazionale delle Ricerche (CNR), Ist Cristallog, Italien
Colloidal lead chalcogenide quantum dots (CQDs) exhibit promising optoelectronic properties for applications in solar cell devices and as thermoelectrics. Herein, we report and discuss a ferroelectric structural distortion, at the picometer scale resolution, in PbS CQDs prepared using both classic and new synthetic pathways. The investigation was performed using synchrotron X-ray total scattering data and advanced methods of analysis that rely on a homo-core-shell model and evaluate the atomic arrangement, stoichiometry, size and morphology of nanocrystals. The CQDs show comparable size-dependent relative elongation, up to 0.7 % of one body diagonal of the cubic rock-salt structure, which corresponds to a rhombohedral lattice deformation. The findings suggest a joint role for the oleate ligands (which induce surface tensile strain) and the Pb(II) lone pair as the driving forces of the deformation. Pb displacements along the [111] direction, which provoke a ferrolectric distortion related to the lattice change, fall in the 0.0 – 0.1 Å range. Overall, the findings suggest the local nature of the metal off-centering, leading to different average displacements which depend on the synthetic conditions.
TidsskriftChemistry Squared
Antal sider14
StatusUdgivet - 2018

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