Spectroscopic signatures of photocharging due to hot-carrier transfer in solutions of semiconductor nanocrystals under low-intensity ultraviolet excitation

John A. McGuire, Milan Sykora, István Robel, Lazaro A. Padilha, Jin Joo, Jeffrey M. Pietryga, Victor I Klimov

Research output: Contribution to journalArticle

73 Citations (Scopus)

Abstract

We show that excitation of solutions of well-passivated PbSe semiconductor nanocrystals (NCs) with ultraviolet (3.1 eV) photons can produce long-lived charge-separated states in which the NC core is left with a nonzero net charge. Since this process is not observed for lower-energy (1.5 eV) excitation, we ascribe it to hot-carrier transfer to some trap site outside the NC. Photocharging leads to bleaching of steady-state absorption, partial quenching of emission, and additional fast time scales in carrier dynamics due to Auger decay of charged single- and multiexciton states. The degree of photocharging, f, saturates at a level that varies from 5 to 15% depending on the sample. The buildup of the population of charged NCs is extremely slow indicating very long, tens of seconds, lifetimes of these charge-separated states. Based on these time scales and the measured onset of saturation of f at excitation rates around 0.05-1 photon per NC per ms, we determine that the probability of charging following a photon absorption event is of the order of 10-4 to 10-3. The results of these studies have important implications for the understanding of photophysical properties of NCs, especially in the case of time-resolved measurements of carrier multiplication.

Original languageEnglish
Pages (from-to)6087-6097
Number of pages11
JournalACS Nano
Volume4
Issue number10
DOIs
Publication statusPublished - Oct 26 2010

Fingerprint

Hot carriers
Nanocrystals
nanocrystals
signatures
Semiconductor materials
excitation
Photons
photons
bleaching
Bleaching
Time measurement
multiplication
charging
Quenching
quenching
time measurement
traps
saturation
life (durability)
decay

Keywords

  • Auger recombination
  • carrier multiplication
  • charge separation
  • charged exciton
  • PbSe nanocrystals
  • photoluminescence
  • trapping

ASJC Scopus subject areas

  • Engineering(all)
  • Materials Science(all)
  • Physics and Astronomy(all)

Cite this

Spectroscopic signatures of photocharging due to hot-carrier transfer in solutions of semiconductor nanocrystals under low-intensity ultraviolet excitation. / McGuire, John A.; Sykora, Milan; Robel, István; Padilha, Lazaro A.; Joo, Jin; Pietryga, Jeffrey M.; Klimov, Victor I.

In: ACS Nano, Vol. 4, No. 10, 26.10.2010, p. 6087-6097.

Research output: Contribution to journalArticle

McGuire, John A. ; Sykora, Milan ; Robel, István ; Padilha, Lazaro A. ; Joo, Jin ; Pietryga, Jeffrey M. ; Klimov, Victor I. / Spectroscopic signatures of photocharging due to hot-carrier transfer in solutions of semiconductor nanocrystals under low-intensity ultraviolet excitation. In: ACS Nano. 2010 ; Vol. 4, No. 10. pp. 6087-6097.
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