Indium insertions in non-stoichiometric copper sulfides, CuxS, and their effect on the localized surface plasmon resonance of the nanocrystals

Abstract

We monitor the stages of the copper indium sulfide growth to ‘counter-dope’ degenerate copper sulfides. We show through an easy and rapid synthesis that indium incorporation into non-stoichiometric copper sulfide (Roxbyite (Cu7S4)) results in its ‘counter-doping’. ‘Counter-doping’ is evidenced by the shift and damping of the LSPR of the resulting compound (Cu5InS4). Indeed, the XRD phases evidenced during the growth of copper indium sulfide starting a reaction with different precursors suggest that the copper indium sulfide growth can occur inside degenerate copper sulfide seeds. We explain the growth mechanism and show ’counter-doping’ with indium, starting the chemical reaction with Roxbyite (Cu7S4) precursors and indium species. The current body of the work is focused on the study of copper indium sulfide and the properties of the indium ratio; here, we use indium as a doping agent resulting for the first time in counter-doped copper sulfides. Despite being suggested in the eighties, doping of non-stoichiometric copper sulfide has never been achieved and could result in more stable chalcogenides with close to ideal band gap for solar cell applications.