Type-II core/shell CdS/ZnSe nanocrystals: Synthesis, electronic structures, and spectroscopic properties

Sergei A. Ivanov, Andrei Piryatinski, Jagjit Nanda, Sergei Tretiak, Kevin R. Zavadil, William O. Wallace, Don Werder, Victor I. Klimov

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Abstract

We report a two-step synthesis of highly luminescent CdS/ZnSe core/shell nanocrystals (emission quantum yields up to 50%) that can produce efficient spatial separation of electrons and holes between the core and the shell (type-II localization regime). Our synthesis involves fabrication of cubic-singony CdS core particles that are subsequently overcoated with a layer of ZnSe in the presence of surfactant-ligands in a noncoordinating solvent. Studies of different growth regime of the ZnSe shell indicate that one approach to obtaining high emission efficiencies is through alloying the CdS/ZnSe interface with CdSe, which leads to the formation of an intermediate ZnCdSe layer with a graded composition. We perform theoretical modeling of these core/shell nanocrystals using effective mass approximation and applying first-order perturbation theory for treating both direct electron-hole coupling and the core/shell interface-polarization effects. Using this model we determine the range of geometrical parameters of the core/shell structures that result in a type-ll localization regime. We further applied this model to evaluate the degree of electron-hole spatial separation (quantified in terms of the electron-hole overlap integral) based on measured emission wavelengths. We also discuss the potential applicability of these nanocrystals in lasing technologies and specifically the possibility of single-exciton optical gain in type-II nanostructures.

Original languageEnglish
Pages (from-to)11708-11719
Number of pages12
JournalJournal of the American Chemical Society
Volume129
Issue number38
DOIs
Publication statusPublished - Sep 26 2007

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ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

Cite this

Ivanov, S. A., Piryatinski, A., Nanda, J., Tretiak, S., Zavadil, K. R., Wallace, W. O., Werder, D., & Klimov, V. I. (2007). Type-II core/shell CdS/ZnSe nanocrystals: Synthesis, electronic structures, and spectroscopic properties. Journal of the American Chemical Society, 129(38), 11708-11719. https://doi.org/10.1021/ja068351m