A structural prediction of copper sulfide and study of its electronic properties and vacancy forming trend using density functional theory

Abstract

The focus of this research is on the material challenges in photovoltaic. Copper Sulfide (Cu2 S) has been regarded as a potential solar absorber materials in photovoltaic industry. Despite its simple composition, it is a complex material. Copper atoms are mobile in Cu2 S crystals facilitating copper vacancies; hence promote Cu-deficient non-stoichiometric Cux S. Majority of the present work is directed towards understanding the stability issue related with Cu2 S/Cux S. We used density functional theory systematically to predict acanthite like structure as ground state structure of Cu2 S. The crystal structure of acanthite Cu2 S is much simpler than the experimentally observed low chalcocite, though electronic structures are similar with Cu-d showing high dominance in valence band. Theoretically we find that both structures show a tendency of forming Cu-vacancy. As it becomes p-type with Cu vacancy, band gap also increases. To understand about the effect of doping in Cu 2 S, tin and oxygen doping have been studied.