Abstract
CdSe nanoplatelets have large extinction coefficients and, at low temperatures, very short photoluminescence lifetimes. To explain these observations, the giant oscillator strength (GOST) effect has been hypothesized to exist in such semiconductor nanoplatelets. In principle, suppression of phonon scattering can increase the area of coherent exciton motion up to the full size of the nanoplatelet, increasing oscillator strength proportional to its size. Yet at high temperatures, the measured area of exciton motion as estimated from various photophysical methods is much smaller than the size of nanoplatelets and insensitive to nanoplatelet size. To examine the emergence of this discrepancy, this work uses temperature-dependent measurements of steady-state absorption, transient optical bleaching, and the optical Stark effect. Although the excitonic oscillator strength (and size) does increase somewhat at reduced temperature, a large difference remains between the area of coherent exciton motion and the entire nanoplatelet area. These measurements indicate that the area of coherent exciton center-of-mass motion does not increase sufficiently to explain observed rapid radiative lifetimes in CdSe nanoplatelets at 3 K. Instead, the data are consistent with localization of excitons to areas much smaller than whole NPLs.
Original language | English (US) |
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Pages (from-to) | 4601-4608 |
Number of pages | 8 |
Journal | Journal of Physical Chemistry C |
Volume | 127 |
Issue number | 9 |
DOIs | |
State | Published - Mar 9 2023 |
Funding
The submitted manuscript has been created by UChicago Argonne, LLC, Operator of Argonne National Laboratory (“Argonne”). Argonne, a U.S. Department of Energy Office of Science laboratory, is operated under Contract No. DE-AC02-06CH11357. The U.S. Government retains for itself, and others acting on its behalf, a paid-up nonexclusive, irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf on the Government. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan. http://energy.gov/downloads/doe-public-access-plan . Acknowledgments Work performed at the Center for Nanoscale Materials, a U.S. Department of Energy Office of Science User Facility, was supported by the U.S. DOE, Office of Basic Energy Sciences, under Contract DE-AC02-06CH11357.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- General Energy
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films