TY - JOUR
T1 - Reexamination of the Giant Oscillator Strength Effect in CdSe Nanoplatelets
AU - Diroll, Benjamin T.
AU - Schaller, Richard D.
N1 - Funding Information:
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
Funding Information:
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.
Publisher Copyright:
© 2023 UChicago Argonne, LLC, Operator of Argonne National Laboratory. Published by American Chemical Society.
PY - 2023/3/9
Y1 - 2023/3/9
N2 - 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.
AB - 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.
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U2 - 10.1021/acs.jpcc.2c08079
DO - 10.1021/acs.jpcc.2c08079
M3 - Article
AN - SCOPUS:85149844049
SN - 1932-7447
VL - 127
SP - 4601
EP - 4608
JO - Journal of Physical Chemistry C
JF - Journal of Physical Chemistry C
IS - 9
ER -