Anomalous Independence of Multiple Exciton Generation on Different Group IV-VI Quantum Dot Architectures

M. Tuan Trinh, Leo Polak, Juleon M. Schins, Arjan J. Houtepen, Roman Vaxenburg, Georgy I. Maikov, Gal Grinbom, Aaron G. Midgett, Joseph M. Luther, Matthew C. Beard, Arthur J. Nozik, Mischa Bonn, Efrat Lifshitz, Laurens D.A. Siebbeles

Research output: Contribution to journalArticlepeer-review

57 Scopus Citations

Abstract

Multiple exciton generation (MEG) in PbSe quantum dots (QDs), PbSe xS1-x alloy QDs, PbSe/PbS core/shell QDs, and PbSe/PbSeyS1-y core/alloy-shell QDs was studied with time-resolved optical pump and probe spectroscopy. The optical absorption exhibits a red-shift upon the introduction of a shell around a PbSe core, which increases with the thickness of the shell. According to electronic structure calculations this can be attributed to charge delocalization into the shell. Remarkably, the measured quantum yield of MEG, the hot exciton cooling rate, and the Auger recombination rate of biexcitons are similar for pure PbSe QDs and core/shell QDs with the same core size and varying shell thickness. The higher density of states in the alloy and core/shell QDs provide a faster exciton cooling channel that likely competes with the fast MEG process due to a higher biexciton density of states. Calculations reveal only a minor asymmetric delocalization of holes and electrons over the entire core/shell volume, which may partially explain why the Auger recombination rate does not depend on the presence of a shell.

Original languageAmerican English
Pages (from-to)1623-1629
Number of pages7
JournalNano Letters
Volume11
Issue number4
DOIs
StatePublished - 2011

NREL Publication Number

  • NREL/JA-5900-51627

Keywords

  • auger recombination
  • hot exciton cooling
  • multiple exciton generation
  • quantum dot architecture

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