Electronically active impurities in colloidal quantum dot solids

Graham H. Carey, Illan J. Kramer, Pongsakorn Kanjanaboos, Gabriel Moreno-Bautista, Oleksandr Voznyy, Lisa Rollny, Joel A. Tang, Sjoerd Hoogland, Edward H. Sargent*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

30 Scopus citations


Colloidal quantum dot films have seen rapid progress as active materials in photodetection, light emission, and photovoltaics. Their processing from the solution phase makes them an attractive option for these applications due to the expected cost reductions associated with liquid-phase material deposition. Colloidally stable nanoparticles capped using long, insulating aliphatic ligands are used to form semiconducting, insoluble films via a solid-state ligand exchange in which the original ligands are replaced with short bifunctional ligands. Here we show that this ligand exchange can have unintended and undesired side effects: a high molecular weight complex can form, containing both lead oleate and the shorter conductive ligand, and this poorly soluble complex can end up embedded within the colloidal quantum dot (CQD) active layer. We further show that, by adding an acidic treatment during film processing, we can break up and wash away these complexes, producing a higher quality CQD solid. The improved material leads to photovoltaic devices with reduced series resistance and enhanced fill factor relative to controls employing previously reported CQD solids. (Figure Presented).

Original languageEnglish (US)
Pages (from-to)11763-11769
Number of pages7
JournalACS nano
Issue number11
StatePublished - Nov 25 2014


  • Colloidal quantum dot
  • Complex
  • Electroluminescence
  • Impurities
  • Ligands
  • Photovoltaics

ASJC Scopus subject areas

  • General Engineering
  • General Physics and Astronomy
  • General Materials Science


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