Ensemble brightening and enhanced quantum yield in size-purified silicon nanocrystals

Joseph B. Miller, Austin R. Van Sickle, Rebecca J. Anthony, Daniel M. Kroll, Uwe R. Kortshagen, Erik K. Hobbie

Research output: Contribution to journalArticlepeer-review

85 Scopus citations

Abstract

We report on the quantum yield, photoluminescence (PL) lifetime, and ensemble photoluminescent stability of highly monodisperse plasma-synthesized silicon nanocrystals (SiNCs) prepared though density-gradient ultracentrifugation in mixed organic solvents. Improved size uniformity leads to a reduction in PL line width and the emergence of entropic order in dry nanocrystal films. We find excellent agreement with the anticipated trends of quantum confinement in nanocrystalline silicon, with a solution quantum yield that is independent of nanocrystal size for the larger fractions but decreases dramatically with size for the smaller fractions. We also find a significant PL enhancement in films assembled from the fractions, and we use a combination of measurement, simulation, and modeling to link this 'brightening' to a temporally enhanced quantum yield arising from SiNC interactions in ordered ensembles of monodisperse nanocrystals. Using an appropriate excitation scheme, we exploit this enhancement to achieve photostable emission.

Original languageEnglish (US)
Pages (from-to)7389-7396
Number of pages8
JournalACS nano
Volume6
Issue number8
DOIs
StatePublished - Aug 28 2012

Keywords

  • nanocrystalline silicon
  • photoluminescent stability
  • polydispersity
  • quantum yield

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