On-Demand Stoichiometry Control of Copper Sulfide Nanocrystals with Omni-Tunable Semiconductor Properties

The duration of the project was 2 years. electronic properties of electronically coupled copper sulfide nanocrystals Cu2-xS NCs assemblies including their structural, optical, electrical, and thermoelectrical characteristics as a function of atomic stoichiometry of the material were investigated. The electronically coupled assemblies of Cu2-xS NCs in thin films were attained by removing the original long oleic amine ligands employed during the synthetic procedure after assemblies of NCs were formed. Following, the stoichiometric composition or x for the electronically coupled Cu2-xS NCs assemblies was controlled by immersing the solid thin film into a solution containing Cu(I) complex. As Cu gradually incorporated into the copper deficient sites of Cu2-xS NCs, x could be controlled. Consequently, NIR absorbance of the Cu2-xS NC assemblies as well as their electrical conductivity and thermoelectric Seebeck coefficient could be changed systematically with the control in x. Overall, room temperature thermoelectrical power factor as high as 33.1 W/K2m could be obtained from electronically coupled assemblies of Cu2-xS NCs with x = 0.02.