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Jeffrey Pietryga1

1, Los Alamos National Laboratory, Los Alamos, New Mexico, United States

The use of solution-synthesized semiconductor nanocrystals (NCs) in optoelectronic devices inevitably requires postsynthetic chemical surface treatments to allow for efficient charge transport in NC films. In the case of lead chalcogenide (PbE; E = S, Se, Te) NCs, such treatments are invariably applied after the NCs are already deposited, typically requiring the film to be built up by repetitive deposition steps to achieve device-relevant thicknesses. This represents a critical hurdle in progress toward exploiting fast, inexpensive and highly scalable solution-based fabrication processes, like spray or knife-edge deposition, especially for intriguing applications such as solar cells and sensors that require films >1 μm thick. Such considerations have driven the development of in-solution surface treatments for a range of other NC materials, but corresponding advances for PbE NCs have lagged dramatically behind. Here, we describe a universal method for fast, complete, in-solution exchange of the surface ligands of PbE NCs with a wide range of anions and small ligands, resulting in a NC “ink” suitable for single-step deposition of conductive films of unprecedented thickness. Optical studies of these inks reveal fascinating complexity in the interactions of the NCs and ligands that suggest that far from being the enemy of NC devices, ligands offer a facile and versatile means for fine tuning of NC and NC film electronic properties. In this talk, we discuss how concepts borrowed from organometallic complexes help to elucidate the complex effects ligands have on NC properties, and how we might exploit this understanding toward realization of high-performance devices.

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