(651f) Controllable Synthesis of Cu2-X E (E=S, Se) Nanocrystals with Localized Surface Plasmon Resonance and Investigation of Conductivity of NC Thin Films

Inorganic nanocrystals (NCs) are of great interest due to their attractive optical, electronic and optoelectronic properties. Metal nanoparticles (NPs) exhibit localized surface plasmon resonance (LSPR) when photons induce  oscillation of the free electrons in conduction band at resonant frequencies. However, in semiconductors, most electrons are confined to the filled valence band and LSPR is not observed. Non-stoichiometric Cu_2-xS and Cu_2-xSe NCs have a high concentration of free holes in the valance band. Recently, LSPR was observed in these heavily self-doping semiconductor NCs. Here, we demonstrate a facile method for controllable synthesis of Cu_2-xS and Cu_2-xSe NCs with superior LSPR. Moreover, we studied the electrical conductivity of solution-processed Cu_2-xS and Cu_2-xSe NCs thin film in ITO-NC film-Al devices. After chemical post-treatment to displace the long-chain surface ligands attached to the particle surfaces, the nanocrystal thin films show surprisingly high electrical conductivity. As a result, they show promise for use in solution-processed field-effect transistors.