Nongeminate Radiative Recombination of Free Charges in Cation-Exchanged PbS Quantum Dot Films

Justin Johnson, Matthew Beard, Ashley Marshall

Research output: Contribution to journalArticlepeer-review

9 Scopus Citations


Using photoluminescence (PL) spectroscopy we explore the radiative recombination pathways in PbS quantum dots (QDs) synthesized by two methods. We compare conventionally synthesized PbS from a PbO precursor to PbS synthesized using cation-exchange from CdS QDs. We show that strongly coupled films of PbS QDs from the cation-exchange luminesce with significant efficiency at room temperature. This is in stark contrast to conventional PbS QDs, which have exceedingly weak room temperature emission. Moreover, the power dependence of the emission is quadratic, indicating bimolecular radiative recombination that is reasonably competitive with trap-assisted recombination, a feature previously unreported in coupled PbS QD films. We interpret these results in terms of a greatly reduced defect concentration for cation-exchanged QDs that mitigates the influence of trap-assisted recombination. Cation-exchanged QDs have recently been employed in highly efficient and air-stable lead chalcogenide QD devices, and the reduced number of trap states inferred here may lead to improved current collection and higher open circuit voltage.

Original languageAmerican English
Pages (from-to)75-80
Number of pages6
JournalChemical Physics
StatePublished - 1 Jun 2016

Bibliographical note

Publisher Copyright:
© 2015 Elsevier B.V. All rights reserved.

NREL Publication Number

  • NREL/JA-5900-64153


  • Bimolecular recombination
  • Nanocrystals
  • PbS
  • Photoluminescence
  • Quantum dots


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