Electronic and optical performance of Ni-doped FeS2 nanocrystals for photovoltaic applications

Abstract

Systematic ab-initio investigations were used to explore whether the electronic and optical behaviors of iron pyrite can achieve by alloying with nickel. The results show a band gap increase to a value of 1.24 eV and a high-absorption coefficient of α ~ ≥7.5*105 cm−1. Ni doping improves n-type conductivity and charge carriers’ mobility is averaging (0.65 ± 0.04) Ω−1.cm−1 in the visible range. We observe that the anti-bonding S-3Pppσ* band states are at the origin of the band gap variation. Indeed, a sensitive reduction in the number of sulfur bonds in iron pyrite can have a significant effect on the absorption threshold leading, consequently, to the optical gap of 1.45 eV due to the formation of covalent S–S interaction. So that, all-optical properties were examined by the study of critical peaks contributions that were identified by partitioning the dielectric function spectra. Hence, the incorporation of Ni in FeS2 lattice improves properties of a buffer layer best matched in a heterostructure with Cu2ZnSnS4 (CZTS) or p-type crystalline silicon (c-Si) based solar cells.