High-efficiency carrier multiplication and ultrafast charge separation in semiconductor nanocrystals studied via time-resolved photoluminescence

Richard D Schaller, Milan Sykora, Sohee Jeong, Victor I Klimov

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155 Citations (Scopus)

Abstract

We demonstrate novel methods for the study of multiple exciton generation from a single photen absorption event (carrier multiplication) in semiconductor nanocrystals (or nanocrystal quantum dots) that are complementary to our previously reported transient absorption method. By monitoring the time dependence of photoluminescence (PL) from CdSe nanocrystals via time-correlated single photon counting, we find that carrier multiplication is observable due to the Auger decay of biexcitons. We compare these data with similar studies using transient absorption and find that the two methods give comparable results. In addition to the observation of dynamical signatures of carrier multiplication due to the Auger decay, we observe spectral signatures of multiple excitons produced from the absorption of a single photon. PL spectra at short times following excitation with high-energy photons are red-shifted compared to the single-exciton emission band, which is consistent with previous observations of significant exciton-exciton interactions in nanocrystals. We then show using a combination of transient absorption and time-resolved PL studies that charge transfer between a nanocrystal and a Ru-based catalyst model compound takes place on a time scale that is faster than Auger recombination time constants, which points toward a possible design of donor-acceptor assemblies that can be utilized to take advantage of the carrier multiplication process.

Original languageEnglish
Pages (from-to)25332-25338
Number of pages7
JournalJournal of Physical Chemistry B
Volume110
Issue number50
DOIs
Publication statusPublished - Dec 21 2006

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polarization (charge separation)
multiplication
Excitons
Nanocrystals
Photoluminescence
nanocrystals
excitons
Semiconductor materials
photoluminescence
Photons
photons
spectral signatures
Beam plasma interactions
decay
assemblies
Semiconductor quantum dots
time constant
time dependence
Charge transfer
counting

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Cite this

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abstract = "We demonstrate novel methods for the study of multiple exciton generation from a single photen absorption event (carrier multiplication) in semiconductor nanocrystals (or nanocrystal quantum dots) that are complementary to our previously reported transient absorption method. By monitoring the time dependence of photoluminescence (PL) from CdSe nanocrystals via time-correlated single photon counting, we find that carrier multiplication is observable due to the Auger decay of biexcitons. We compare these data with similar studies using transient absorption and find that the two methods give comparable results. In addition to the observation of dynamical signatures of carrier multiplication due to the Auger decay, we observe spectral signatures of multiple excitons produced from the absorption of a single photon. PL spectra at short times following excitation with high-energy photons are red-shifted compared to the single-exciton emission band, which is consistent with previous observations of significant exciton-exciton interactions in nanocrystals. We then show using a combination of transient absorption and time-resolved PL studies that charge transfer between a nanocrystal and a Ru-based catalyst model compound takes place on a time scale that is faster than Auger recombination time constants, which points toward a possible design of donor-acceptor assemblies that can be utilized to take advantage of the carrier multiplication process.",
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