First-Principles Studies on Structural, Electronic and Optical Properties of Fe-doped NiS2 Counter Electrode for DyeSensitised Solar Cells using DFT+U

Abstract

The structural, electronic, and optical properties of nickel disulfide (NiS₂) and iron (Fe)-doped NiS₂ were computed by using first-principles calculations through the density functional theory (DFT) method. The Fe was used as a dopant element to understand the behaviour and the key mechanism of Fe-doped NiS₂ as a counter electrode in dye-sensitised solar cells (DSSC). The results indicated that the structural properties of the NiS₂ as the cubic crystal structure with the space group Pa3 (205) (pyrite structure type) agree with experimental data. The density of states (DOS) of NiS₂ and Fe-doped NiS₂ shows a gapless bandgap due to Mott-Hubbard insulator behavior. As for optical properties, the optical absorption of NiS₂ is shifted towards the infrared (IR) region when doping with Fe while the conductivity of Fe-doped NiS₂ is slightly higher in conductivity. These optical properties show that Fe-doped NiS₂ is suitable for the photocatalytic activity and may provide an excellent electron charge transfer for a counter electrode in DSSC.