Journal
ACS NANO
Volume 13, Issue 8, Pages 8589-8596Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acsnano.9b02008
Keywords
nanoplatelets; exciton size; quantum confinement; diamagnetic shift; electronic structure
Categories
Funding
- National Science Foundation [DMREF-1629383, DMREF-1629361, DGE-1324585, DMR-1157490, 1644779]
- U.S. Department of Energy
- State of Florida
- U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences [DE-FG02-99ER14999, DE-AC02-06CH11357]
- [DE-AC02-05CH11231]
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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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