Stoichiometric Doping of Copper Sulfide Nanocrystals Assemblies with Tunable Electronic Properties

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Abstract:

In this project, we developed a versatile conversion platform that allows delicate control in the atomic stoichiometry for highly coupled Cu2-xS NCs assemblies with tunable electronic properties including the optical properties, charge transport properties, and thermoelectrical properties. The control in the atomic stoichiometry was done through two distinct methods. First, the control was done by directly inserting/extracting copper into/from the assemblies using a solution phase chemical agent. Specifically, the stoichiometry of Cu2-xS NCs assemblies could be controlled from x = 0.1 to 0.9 . With increasing x, we confirmed that the absorbance at near IR regime, electrical conductivity, and Seebeck coefficient changed systematically, leading to the maximal thermoelectric power factor from a film of Cu2-xS NCs at an optimal doping condition yielding x = 0.1. Second, the atomic composition for assemblies of Cu2-xS NC (x = 0.9) could also be controlled by introducing monovalent heterocations (such as lithium or sodium) into the assemblies and reversibly extracting these cations from the assemblies through electrochemical method. The electrochemically controlled uptake and release of the cations for assemblies of Cu2-xS NC allow systematic tuning in the characteristic near-infrared absorbance of the thin-film assemblies based on localized surface plasmon resonance.

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