Ultrafast percolative transport dynamics in silicon nanocrystal films

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DOIResolve DOI: http://doi.org/10.1103/PhysRevB.83.085403
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TypeArticle
Journal titlePhysical Review B - Condensed Matter and Materials Physics
ISSN1098-0121
Volume83
Issue8
Article number85403
AbstractWe have applied time-resolved terahertz (THz) spectroscopy to probe ultrafast conduction dynamics of photoexcited carriers in silicon nanocrystal films with a wide range of nanocrystal sizes and concentrations. The picosecond THz conductivity reveals microscopic photocarrier motion with significant interface scattering within the nanocrystals, as well as percolative transport between nanocrystals. In films with silicon filling fractions above the percolation threshold, we observe a transition from long-range internanocrystal transport immediately after photoexcitation to increased carrier localization over a 50-ps time scale due to accumulation of charges at interface defect sites. However, in films with silicon filling fractions below the percolation threshold, transport between nanocrystals is strongly suppressed at all times. Finally, we estimate effective carrier diffusion lengths of 60 to 130 nm for the silicon nanocrystal composites with silicon filling fractions above the percolation threshold, making such films promising candidates for active layers in photovoltaic devices. © 2011 American Physical Society.
Publication date
LanguageEnglish
AffiliationNational Research Council Canada (NRC-CNRC); National Institute for Nanotechnology
Peer reviewedYes
NPARC number21271996
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Record identifierfb08d5cc-2691-4af2-978a-4f63faa02fde
Record created2014-05-16
Record modified2016-05-09
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