The optical phonon spectrum of CdSe colloidal quantum dots

The direct coupling of excited electronic states to optical phonons in single CdSe colloidal quantum dots is explored using both photoluminescence emission and excitation spectroscopies. We find a broad optical phonon spectrum associated with a single fine structure state. Multiple peaks in the opti...

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Bibliographic Details
Published in:Physical chemistry chemical physics : PCCP 2014-08, Vol.16 (32), p.16957-16961
Main Authors: Fernée, Mark J, Sinito, Chiara, Mulvaney, Paul, Tamarat, Philippe, Lounis, Brahim
Format: Article
Language:English
Subjects:
Cadmium selenides
Colloids
Emission spectroscopy
Excitation
Intermetallics
Phonons
Quantum dots
Sidebands
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Summary:The direct coupling of excited electronic states to optical phonons in single CdSe colloidal quantum dots is explored using both photoluminescence emission and excitation spectroscopies. We find a broad optical phonon spectrum associated with a single fine structure state. Multiple peaks in the optical phonon sideband are ascribed to different optical phonon types emanating from both the core and shell layers. A mixed emission process that involves the simultaneous generation of two different types of optical phonon is also observed. In general, rather than a single mode, each designated phonon type is associated with a dispersed family of modes. Narrow optical phonon sidebands, consistent with the dominant LO mode, are observed in some nanocrystals. A linewidth analysis indicates that optical phonon lifetimes are in the 10 picosecond range. We demonstrate the ability to selectively excite a specific band-edge state by directly exciting its LO phonon sideband.
ISSN:1463-9076
1463-9084
DOI:10.1039/c4cp02022g