As synthesized PbSe quantum dots (QDs) are natively passivated with insulating oleate ligands that must be removed or replaced to form charge conducting QD films for photovoltaic applications. Conventionally, this is accomplished in a layer-by-layer fashion where thin films of oleate capped QDs are exchanged with short-chain thiols, such as ethanedithiol, to build up a film of desired thickness. As an alternative, we developed ligand exchange strategies to terminate the PbSe QDs with cinnamic acid and fluorinated cinnamic acid derivatives in solution. These small, conjugated ligands undergo complete exchange with native oleate ligands and allow for one-step film formation from concentrated solutions using spin coating or drop casting techniques. The different ligands are characterized by their degree of electron donating ability and thereby impact the optical and electrical properties of the resulting QDs and QD films. We compare carrier mobilities for oleate-capped, cinnamic acid capped, and ethanedithiol capped QD films and correlate results with film morphology and other spectroscopic observations.

Colloidal cinnamic acid capped PbSe quantum dots: Solution phase ligand exchange, thin film formation, and electrical conductivity for photovoltaic applications

249th National Meeting (2015)

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