Electronic Properties of Cu2–xSe Nanocrystal Thin Films Treated with Short Ligand (S2–, SCN–, and Cl–) Solutions

Abstract

To exploit interesting electronic properties of colloidal semiconductor nanocrystals (NCs) in thin film devices, replacement of the original bulky ligands attached on the NC surface to short ones is essential. Here, we investigate the electronic properties of thin films of Cu2–xSe NCs treated chemically with short sulfide (S2–), thiocyanate (SCN–), and chloride (Cl–) ligands that are known to yield superior physical properties compared to the first-generation short ligand systems including amines and thioles. Specifically, the study focuses on the impact of ligand treatment on their direct/indirect bandgap and NIR-localized surface plasmon resonance (LSPR) in the near-IR regime as well as their electrical conductivity and thermoelectric properties. While the application of S2– solution resulted in exchange of the original oleylamine (OAm) on NC surface with S2– ligands, use of SCN– and Cl– solutions only removed the original ligands. The different ligands consistently led a red-shift of the direct and ind...