Increasing the band gap of FeS₂by alloying with Zn and applying biaxial strain: A first-principles study

The combined effect of alloying and biaxial strain on atomic structure, as well as electronic and optical properties of FeS₂ was first examined by the first-principles calculation. By allaying with Zn, our results show that the band gap of Fe_1-xZn_xS₂ alloy increases firstly and then decreases with increasing Zn concentration, the maximum enlargement of band gap is ∼0.1 eV. The left shift of the absorption threshold enhances the overall optical absorptivity. By imposing biaxial strain on the Zn-doped FeS₂, the band gap decreases under compressive strain, but increases from 0.95 eV to 1.14 eV under 5% tensile strain. More specially, strain widens the band gap of Zn-doped FeS₂ by ∼0.19 eV, and the overall optical absorptivity is further enhanced by the combination of strain and Zn-doping. With the increase of the band gap by ∼0.29 eV and the high optical absorptivity, FeS₂ is a more promising material for photovoltaic applications.