In-Plane Exciton Radius of Two-Dimensional Colloidal Nanoplatelets
Alexandra Brumberg a, Samantha Harvey a, John Philbin b, Benjamin Diroll c, Byeongdu Lee d, Scott Crooker e, Eran Rabani b, Richard Schaller a c
a Department of Chemistry, Northwestern University, United States, Sheridan Road, 2145, Evanston, United States
b Department of Chemistry, University of California, Berkeley, Berkeley, California 94720, EE. UU., Berkeley, United States
c Argonne National Laboratory, Center for Nanoscale Materials, 9700 South Cass Avenue Bldg 440, Lemont, Illinois 60439, United States
d Argonne National Laboratory, Advanced Photon Source, 9700 South Cass Avenue, Lemont, Illinois 60439, United States
e National High Magnetic Field Laboratory, Los Alamos National Laboratory, United States
Poster, Alexandra Brumberg, 013
Publication date: 6th May 2020

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Colloidal, two-dimensional semiconductor nanoplatelets (NPLs) exhibit quantum confinement in only one dimension, which results in an electronic structure that is significantly altered compared to that of other quantum-confined nanomaterials. Whereas it is often assumed that the lack of quantum confinement in the lateral plane yields a spatially extended exciton, reduced dielectric screening potentially challenges this picture. Here, we implement absorption spectroscopy in pulsed magnetic fields up to 60 T for three different CdSe NPL thicknesses and lateral areas. Based on diamagnetic shifts, we find that the exciton lateral extent is comparable to NPL thickness, indicating that the quantum confinement and reduced screening concomitant with few-monolayer thickness strongly reduces the exciton lateral extent. Atomistic electronic structure calculations of the exciton size for varying lengths, widths, and thicknesses support the substantially smaller in-plane exciton extent.

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