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Title: Thermal Excitation Control over Photon Emission Rate of CdSe Nanocrystals

Abstract

Temperature-dependent photoluminescence lifetimes of electron-hole pairs (excitons) in CdSe nanocrystals are governed by the energetic ordering and spacing of slowly emitting, spin-forbidden "dark" exciton states and rapidly emitting "bright" states. Here, infrared pulses that are resonant with hydrocarbon surface ligand vibrational transitions are shown to offer a route to manipulate the instantaneous emission rate of CdSe nanocrystals at cryogenic temperature. Transient heating of the inorganic nanocrystal core is achieved via resonant excitation of ligand vibrations, followed by heat flow to the nanocrystal lattice. Heating of the nanocrystal core is demonstrated using transient absorption spectroscopy, which shows a time-dependent red-shift of the quantum dot electronic absorption resonances, consistent with heating. Transient heating of the nanocrystal above the bath temperature increases the instantaneous radiative rate of the nanocrystals via a combination of thermal occupation of bright states as well as phonon-assisted emission. The lifetime of this infrared pumped, fast-emitting sample condition is dictated by particle thermalization, which is multiple orders of magnitude shorter lived than the dark exciton state. This work demonstrates the feasibility of using heat control pulses to manipulate electronic recombination rates of excitons.

Authors:
;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1531175
DOE Contract Number:  
AC02-06CH11357
Resource Type:
Journal Article
Journal Name:
Nano Letters
Additional Journal Information:
Journal Volume: 19; Journal Issue: 4
Country of Publication:
United States
Language:
English
Subject:
exciton; heat transfer; infrared; nanocrystal; photoluminescence

Citation Formats

Diroll, Benjamin T., and Schaller, Richard D. Thermal Excitation Control over Photon Emission Rate of CdSe Nanocrystals. United States: N. p., 2019. Web. doi:10.1021/acs.nanolett.8b04847.
Diroll, Benjamin T., & Schaller, Richard D. Thermal Excitation Control over Photon Emission Rate of CdSe Nanocrystals. United States. doi:10.1021/acs.nanolett.8b04847.
Diroll, Benjamin T., and Schaller, Richard D. Mon . "Thermal Excitation Control over Photon Emission Rate of CdSe Nanocrystals". United States. doi:10.1021/acs.nanolett.8b04847.
@article{osti_1531175,
title = {Thermal Excitation Control over Photon Emission Rate of CdSe Nanocrystals},
author = {Diroll, Benjamin T. and Schaller, Richard D.},
abstractNote = {Temperature-dependent photoluminescence lifetimes of electron-hole pairs (excitons) in CdSe nanocrystals are governed by the energetic ordering and spacing of slowly emitting, spin-forbidden "dark" exciton states and rapidly emitting "bright" states. Here, infrared pulses that are resonant with hydrocarbon surface ligand vibrational transitions are shown to offer a route to manipulate the instantaneous emission rate of CdSe nanocrystals at cryogenic temperature. Transient heating of the inorganic nanocrystal core is achieved via resonant excitation of ligand vibrations, followed by heat flow to the nanocrystal lattice. Heating of the nanocrystal core is demonstrated using transient absorption spectroscopy, which shows a time-dependent red-shift of the quantum dot electronic absorption resonances, consistent with heating. Transient heating of the nanocrystal above the bath temperature increases the instantaneous radiative rate of the nanocrystals via a combination of thermal occupation of bright states as well as phonon-assisted emission. The lifetime of this infrared pumped, fast-emitting sample condition is dictated by particle thermalization, which is multiple orders of magnitude shorter lived than the dark exciton state. This work demonstrates the feasibility of using heat control pulses to manipulate electronic recombination rates of excitons.},
doi = {10.1021/acs.nanolett.8b04847},
journal = {Nano Letters},
number = 4,
volume = 19,
place = {United States},
year = {2019},
month = {4}
}