Size-Dependent Asymmetric Auger Interactions in Plasma-Produced n- and p-Type-Doped Silicon Nanocrystals

Rens Limpens, Gregory Pach, David Mulder, Nathan Neale

Research output: Contribution to journalArticlepeer-review

8 Scopus Citations


Nonradiative Auger recombination (AR) tends to dominate carrier dynamics in charged, quantum-confined structures. Consequently, it complicates the practical realization of many semiconductor nanocrystal (NC)-based devices such as light-emitting diodes, photovoltaic cells, and single-photon emitters, in which charged exciton states often occur. To this end, extensive experimental studies on direct band gap NCs have investigated the trion components (both positive and negative) that construct the total AR rate. However, such an analysis has remained elusive for indirect band gap Si NCs. In this study, we investigate AR decay of non-thermal plasma-produced n- and p-type-doped Si NCs. We expand the study over a large NC size range (DNC 3-8 nm), in which n- and p-type doping is achieved by either a substitutional or surface doping effect, respectively. First, we monitor the AR of charge-neutral multiexcitons by measuring the biexciton lifetime (τXX) as a function of the NC size and doping configuration. We show that this method can be used to determine the presence of free carriers for any doped NC system, regardless of the presence/absence of defect channels in the carrier dynamics. Second, we develop a photophysical fitting model to determine the Auger lifetime of the simplest charged states in Si NCs: the negative (τX-) and positive (τX+) trions. Trion lifetimes shorten with increasing quantum confinement, as expected from (1) closer spatial proximity of the interacting charges and (2) increased relaxation of the momentum conservation rule. While both τX- and τX+ are in the nanosecond time regime (and both therefore completely dominate the carrier dynamics), AR with excess holes is faster. This asymmetry is explained by a higher density of valence band states in comparison to the conduction band states, due to effective mass differences between electrons and holes.

Original languageAmerican English
Pages (from-to)5782-5789
Number of pages8
JournalJournal of Physical Chemistry C
Issue number9
StatePublished - 7 Mar 2019

Bibliographical note

Publisher Copyright:
© 2019 American Chemical Society.

NREL Publication Number

  • NREL/JA-5900-73105


  • auger recombination
  • nanocrystal doping
  • non-thermal plasma synthesis
  • Si nanocrystals
  • solar-photochemistry
  • ultrafast spectroscopy


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