Pump-intensity- and shell-thickness-dependent evolution of photoluminescence blinking in individual core/shell CdSe/CdS nanocrystals

Anton V. Malko, Young Shin Park, Siddharth Sampat, Christophe Galland, Javier Vela, Yongfen Chen, Jennifer A. Hollingsworth, Victor I. Klimov, Han Htoon

Research output: Contribution to journalArticle

74 Citations (Scopus)

Abstract

We report a systematic study of photoluminescence (PL) intensity and lifetime fluctuations in individual CdSe/CdS core/shell nanocrystal quantum dots (NQDs) as a function of shell thickness. We show that while at low pump intensities PL blinking in thin-shell (4-7 monolayers, MLs) NQDs can be described by random switching between two states of high (ON) and low (OFF) emissivities, it changes to the regime with a continuous distribution of ON intensity levels at high pump powers. A similar behavior is observed in samples with a medium shell thickness (10-12 MLs) without, however, the PL intensity ever switching to a complete "OFF" state and maintaining ca. 30% emissivity ("gray" state). Further, our data indicate that highly stable, blinking-free PL of thick-shell (15-19 MLs) NQDs ("giant" or g-NQDs) is characterized by nearly perfect Poisson statistics, corresponding to a narrow, shot-noise limited PL intensity distribution. Interestingly, in this case the PL lifetime shortens with increasing pump power and the PL decay may deviate from monoexponential. However, the PL intensity distribution remains shot-noise limited, indicating the absence of significant quantum yield fluctuations at a given pump power intensity during the experimental time window.

Original languageEnglish
Pages (from-to)5213-5218
Number of pages6
JournalNano letters
Volume11
Issue number12
DOIs
Publication statusPublished - Dec 14 2011

Keywords

  • Auger recombination
  • Nanocrystal
  • PL lifetime
  • core/shell heterostructure
  • fluorescence blinking
  • multiexciton

ASJC Scopus subject areas

  • Bioengineering
  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanical Engineering

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  • Cite this

    Malko, A. V., Park, Y. S., Sampat, S., Galland, C., Vela, J., Chen, Y., Hollingsworth, J. A., Klimov, V. I., & Htoon, H. (2011). Pump-intensity- and shell-thickness-dependent evolution of photoluminescence blinking in individual core/shell CdSe/CdS nanocrystals. Nano letters, 11(12), 5213-5218. https://doi.org/10.1021/nl2025272