Photocharging artifacts in measurements of electron transfer in quantum-dot-sensitized mesoporous titania films

Nikolay S. Makarov, Hunter McDaniel, Nobuhiro Fuke, Istvan Robel, Victor I Klimov

Research output: Contribution to journalArticle

22 Citations (Scopus)

Abstract

Transient absorption and time-resolved photoluminescence measurements of high-performance mesoporous TiO2 photoanodes sensitized with CuInSexS2-x quantum dots reveal the importance of hole scavenging in the characterization of photoinduced electron transfer. The apparent characteristic time of this process strongly depends on the local environment of the quantum dot/TiO2 junction due to accumulation of long-lived positive charges in the quantum dots. The presence of long-lived photoexcited holes introduces artifacts due to fast positive-trion Auger decay (60 ps time constant), which can dominate electron dynamics and thus mask true electron transfer. We show that the presence of a redox electrolyte is critical to the accurate characterization of charge transfer, since it enables fast extraction of holes and helps maintain charge neutrality of the quantum dots. Although electron transfer is observed to be relatively slow (19 ns time constant), a high electron extraction efficiency (>95%) can be achieved because in well-passivated CuInSexS2-x quantum dots neutral excitons have significantly longer lifetimes of hundreds of nanoseconds.

Original languageEnglish
Pages (from-to)111-118
Number of pages8
JournalJournal of Physical Chemistry Letters
Volume5
Issue number1
DOIs
Publication statusPublished - Jan 2 2014

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Keywords

  • Auger recombination
  • charge transfer
  • CuInS
  • CuInSe
  • nanocrystal
  • quantum dot
  • sensitized solar cell

ASJC Scopus subject areas

  • Materials Science(all)

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