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  Controlling Charge Carrier Overlap in Type-II ZnSe/ZnS/CdS Core–Barrier–Shell Quantum Dots

Boldt, K., Ramanan, C., Chanaewa, A., Werheid, M., & Eychmüller, A. (2015). Controlling Charge Carrier Overlap in Type-II ZnSe/ZnS/CdS Core–Barrier–Shell Quantum Dots. The Journal of Physical Chemistry Letters, 6(13), 2590-2597. doi:10.1021/acs.jpclett.5b01144.

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Item Permalink: http://hdl.handle.net/21.11116/0000-0005-4A56-8 Version Permalink: http://hdl.handle.net/21.11116/0000-0005-4A5C-2
Genre: Journal Article

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Boldt, Klaus, Author
Ramanan, Charusheela1, Author              
Chanaewa, Alina, Author
Werheid, Matthias, Author
Eychmüller, Alexander, Author
Affiliations:
1Department of Physics and Astronomy, Faculty of Sciences, VU University Amsterdam, The Netherlands, ou_persistent22              

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 Abstract: We describe the synthesis and spectroscopic characterization of colloidal ZnSe/ZnS/CdS nanocrystals, which exhibit a type-II electronic structure and wave function overlap that is strongly dependent on the thickness of the ZnS barrier. Barrier thickness is controlled by both the amount of deposited material and the reaction and annealing temperature of CdS shell growth. The results show that a single monolayer of ZnS mitigates the overlap significantly, while four and more monolayers effectively suppress band edge absorption and emission. Transient absorption spectra reveal a broad distribution of excitons with mixed S and P symmetry, which become allowed due to alloy formation and contribute to charge carrier relaxation across the barrier. We present a model of the core/shell interface based on cation diffusion, which allows one to estimate the extent of the diffusion layer from optical spectra. We describe the synthesis and spectroscopic characterization of colloidal ZnSe/ZnS/CdS nanocrystals, which exhibit a type-II electronic structure and wave function overlap that is strongly dependent on the thickness of the ZnS barrier. Barrier thickness is controlled by both the amount of deposited material and the reaction and annealing temperature of CdS shell growth. The results show that a single monolayer of ZnS mitigates the overlap significantly, while four and more monolayers effectively suppress band edge absorption and emission. Transient absorption spectra reveal a broad distribution of excitons with mixed S and P symmetry, which become allowed due to alloy formation and contribute to charge carrier relaxation across the barrier. We present a model of the core/shell interface based on cation diffusion, which allows one to estimate the extent of the diffusion layer from optical spectra.

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 Dates: 2015
 Publication Status: Published online
 Pages: -
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 Rev. Type: -
 Identifiers: DOI: 10.1021/acs.jpclett.5b01144
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Title: The Journal of Physical Chemistry Letters
  Abbreviation : J. Phys. Chem. Lett.
Source Genre: Journal
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Publ. Info: Washington, DC : American Chemical Society
Pages: - Volume / Issue: 6 (13) Sequence Number: - Start / End Page: 2590 - 2597 Identifier: CoNE: https://pure.mpg.de/cone/journals/resource/1948-7185