Bandgap engineering by cationic disorder: case study on AgBiS2

Abstract

The influence of cationic disorder on the electronic structure of ternary compounds, here exemplified on AgBiS₂ material, is studied by means of accurate first principles periodic density functional theory based calculations. For AgBiS₂ cationic disorder in going from semiconducting matildite to a metallic arrangement crystal structure is found to induce a significant decrease in the band gap, as a result of cation-disorder conduction band tail states penetrating into the matildite bandgap. Properly aligned conduction band minimum and valence band maximum show that cationic disorders lead to a noticeable drop of the former and a slight increase of the latter. The present results indicate that temperature effects triggering cationic disorder will have a beneficial effect on the photoactivity of AgBiS₂ samples provided that the metallic limit is not reached.