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

Research output: Contribution to journalArticlepeer-review

30 Scopus citations


© 2014 American Chemical Society. 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 12 2014
Externally publishedYes

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledged KAUST grant number(s): KUS-11-009-21
Acknowledgements: We thank Ikeuchi USA for useful discussions on the appropriate nozzles to use for our materials and solvents. Computations were performed using the BlueGene/Q supercomputer at the SciNet HPC Consortium provided through the Southern Ontario Smart Computing Innovation Platform (SOSCIP). The SOSCIP consortium is funded by the Ontario Government and the Federal Economic Development Agency for Southern Ontario. This research is supported in part by the IBM Canada Research and Development Center. This publication is based in part on work supported by Award KUS-11-009-21, made by King Abdullah University of Science and Technology (KAUST). P.K., G.M.B., and J.A.T. prepared and analyzed SS NMR data. I.J.K., G.C., and L.R. prepared and analyzed FTIR data. O.V. built the DFT models. G.C. executed solubility studies. S.H. did photoluminescence studies. G.C. and I.J.K. prepared photovoltaic devices and measured both the solar cell characteristics and electroluminescence characteristics. G.C., I.J.K., and E.H.S. wrote the manuscript. E.H.S. reviewed all results and edited the manuscript. All authors commented on the paper and have given approval to the final version of the manuscript.
This publication acknowledges KAUST support, but has no KAUST affiliated authors.


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