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Probing Fundamental Excitonic Intera...

Gellen, Tobias,

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Probing Fundamental Excitonic Interactions in Semiconductor Nanocrystals Using Coherent Multidimensional Spectroscopy /

Record Type:	Electronic resources : Monograph/item
Title/Author:	Probing Fundamental Excitonic Interactions in Semiconductor Nanocrystals Using Coherent Multidimensional Spectroscopy // Tobias Gellen.
Author:	Gellen, Tobias,
Description:	1 electronic resource (120 pages)
Notes:	Source: Dissertations Abstracts International, Volume: 85-01, Section: B.
Contained By:	Dissertations Abstracts International85-01B.
Subject:	Physical chemistry. -
Online resource:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=30309716
ISBN:	9798379773854

Probing Fundamental Excitonic Interactions in Semiconductor Nanocrystals Using Coherent Multidimensional Spectroscopy /
Gellen, Tobias,

Probing Fundamental Excitonic Interactions in Semiconductor Nanocrystals Using Coherent Multidimensional Spectroscopy /Tobias Gellen. - 1 electronic resource (120 pages)

Source: Dissertations Abstracts International, Volume: 85-01, Section: B.

The finite spectral line width of an ensemble of CdSe nanocrystals arises from size and shape inhomogeneity and the single-nanocrystal spectrum itself. This line width directly limits the performance of nanocrystal-based devices, yet most optical measurements cannot resolve the underlying contributions. Two-dimensional electronic spectroscopy (2D ES) is used to measure the line width of the band-edge exciton of CdSe nanocrystals as a function of radii and surface chemistry. Findings demonstrate that homogeneous width decreases for increasing nanocrystal radius and that surface chemistry plays a critical role in controlling this line width. To explore the hypothesis that unpassivated trap states serve to broaden the homogeneous line width, and to explain its size-dependence, 3D ES is used to identify the spectral signatures of exciton--phonon coupling to optical and acoustic phonons. The results indicate enhanced coupling to optical phonon modes for nanocrystals that lack electron-passivating ligands, suggesting that localized surface charges enhance exciton--phonon coupling via the Frohlich interaction. Lastly, the data reveal that spectral diffusion contributes negligibly to the homogeneous line width on sub-nanosecond timescales.A recent theoretical study proposed that two-quantum two-dimensional electronic spectroscopy (2Q 2D ES) should be a background-free probe of post-Hartree--Fock electronic correlations. A spectrometer for ultrabroadband 2Q 2D ES measurements is described that is passively phase stable and uses only beamsplitters and mirrors. The design increases the spectral range of two-quantum methods by about one order of magnitude. Spectra of two molecular samples are presented that not only reveal distinct 2Q signatures, but also demonstrate that solvent signals confound the spectra. Despite strong solvent response, the results demonstrate that 2Q spectra can provide a singular probe of doubly excited states.The acoustic and optical phonons in the CdSe nanocrystal modulate the absorption spectrum and are detectable as coherent oscillations in time-resolved spectroscopy. It has been unclear if the coupling mechanism of each phonon results from amplitude modulation arising from non-Condon coupling or frequency modulation arising from conventional Franck--Condon coupling. Resolving this mechanistic detail would benefit any optoelectronic device that relies on finely tailored nanocrystal spectra, or an optical application that exploits the nanocrystal's high extinction coefficient. Previous efforts have used pump-probe techniques to assign the modulation mechanism but these studies focused on a small subset of the known phonons in the CdSe nanocrystal. Fully phased multidimensional electronic spectra are used to expand on that initial study by assigning the modulation mechanism for all of the phonons in the CdSe nanocrystal. Clear diagonal nodes are observed in the beating maps for both acoustic and optical phonons, suggesting that all phonons frequency-modulate the absorption spectrum in the CdSe nanocrystal. Simulations using line shape functions support this conclusion.

English

ISBN: 9798379773854Subjects--Topical Terms:

1981412
Physical chemistry.
Subjects--Index Terms:

Semiconductor

Probing Fundamental Excitonic Interactions in Semiconductor Nanocrystals Using Coherent Multidimensional Spectroscopy /
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100 1 $a Gellen, Tobias, $e author. $3 3816067
245 1 0 $a Probing Fundamental Excitonic Interactions in Semiconductor Nanocrystals Using Coherent Multidimensional Spectroscopy / $c Tobias Gellen.
264 1 $a Ann Arbor : $b ProQuest Dissertations & Theses, $c 2023
300 $a 1 electronic resource (120 pages)
336 $a text $b txt $2 rdacontent
337 $a computer $b c $2 rdamedia
338 $a online resource $b cr $2 rdacarrier
500 $a Source: Dissertations Abstracts International, Volume: 85-01, Section: B.
500 $a Advisors: Turner, Daniel B. Committee members: Tuckerman, Mark; Traaseth, Nate; Woerpel, Keith; Ward, Mike.
502 $b Ph.D. $c New York University $d 2023.
520 $a The finite spectral line width of an ensemble of CdSe nanocrystals arises from size and shape inhomogeneity and the single-nanocrystal spectrum itself. This line width directly limits the performance of nanocrystal-based devices, yet most optical measurements cannot resolve the underlying contributions. Two-dimensional electronic spectroscopy (2D ES) is used to measure the line width of the band-edge exciton of CdSe nanocrystals as a function of radii and surface chemistry. Findings demonstrate that homogeneous width decreases for increasing nanocrystal radius and that surface chemistry plays a critical role in controlling this line width. To explore the hypothesis that unpassivated trap states serve to broaden the homogeneous line width, and to explain its size-dependence, 3D ES is used to identify the spectral signatures of exciton--phonon coupling to optical and acoustic phonons. The results indicate enhanced coupling to optical phonon modes for nanocrystals that lack electron-passivating ligands, suggesting that localized surface charges enhance exciton--phonon coupling via the Frohlich interaction. Lastly, the data reveal that spectral diffusion contributes negligibly to the homogeneous line width on sub-nanosecond timescales.A recent theoretical study proposed that two-quantum two-dimensional electronic spectroscopy (2Q 2D ES) should be a background-free probe of post-Hartree--Fock electronic correlations. A spectrometer for ultrabroadband 2Q 2D ES measurements is described that is passively phase stable and uses only beamsplitters and mirrors. The design increases the spectral range of two-quantum methods by about one order of magnitude. Spectra of two molecular samples are presented that not only reveal distinct 2Q signatures, but also demonstrate that solvent signals confound the spectra. Despite strong solvent response, the results demonstrate that 2Q spectra can provide a singular probe of doubly excited states.The acoustic and optical phonons in the CdSe nanocrystal modulate the absorption spectrum and are detectable as coherent oscillations in time-resolved spectroscopy. It has been unclear if the coupling mechanism of each phonon results from amplitude modulation arising from non-Condon coupling or frequency modulation arising from conventional Franck--Condon coupling. Resolving this mechanistic detail would benefit any optoelectronic device that relies on finely tailored nanocrystal spectra, or an optical application that exploits the nanocrystal's high extinction coefficient. Previous efforts have used pump-probe techniques to assign the modulation mechanism but these studies focused on a small subset of the known phonons in the CdSe nanocrystal. Fully phased multidimensional electronic spectra are used to expand on that initial study by assigning the modulation mechanism for all of the phonons in the CdSe nanocrystal. Clear diagonal nodes are observed in the beating maps for both acoustic and optical phonons, suggesting that all phonons frequency-modulate the absorption spectrum in the CdSe nanocrystal. Simulations using line shape functions support this conclusion.
546 $a English
590 $a School code: 0146
650 4 $a Physical chemistry. $3 1981412
650 4 $a Nanoscience. $3 587832
650 4 $a Materials science. $3 543314
653 $a Semiconductor
653 $a Nanocrystals
653 $a Multidimensional spectroscopy
653 $a Excitonic interactions
653 $a 2Q signatures
690 $a 0494
690 $a 0565
690 $a 0794
710 2 $a New York University. $b Chemistry. $e degree granting institution. $3 3816068
720 1 $a Turner, Daniel B. $e degree supervisor.
773 0 $t Dissertations Abstracts International $g 85-01B.
790 $a 0146
791 $a Ph.D.
792 $a 2023
856 4 0 $u https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=30309716