Increasing the band gap of FeS2 by alloying with Zn and applying biaxial strain: A first-principles study

•The combined effect of doping and biaxial strain on the physical properties of FeS2 was studied.•The band gap of FeS2 is widen by ∼0.29 eV under 5% tensile strain with Zn alloying at 6.25% concentration.•Alloying with Zn and biaxial tensile strain effectively improve the electronic and optical properties of FeS2.

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 Fe1−xZnxS2 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.