Modulating Properties of Cu ₂ ZnSnS ₄ Thin Films With Broad Mg‐Doping Concentration by Sol–Gel Method

ABSTRACT Mg‐doped Cu 2 ZnSnS 4 films were prepared by sol–gel method with varying Mg concentration. The effects of Mg concentration on the phase structure, optical properties, and electrical properties were investigated. The incorporation of Mg did not alter the phase structure but caused a shift of diffraction peaks to larger angles and a slight reduction in the bandgap as the Mg concentration increased. Sample S3‐4% exhibited higher lattice strain, whereas sample S4‐6% presented the lowest lattice strain value of 0.63. XPS results demonstrate that the chemical valence states of the Cu, Zn, Sn, and S elements remained unchanged in the Cu 2 Mg x Zn (1‐x) SnS 4 compounds. Additionally, the incorporation of Mg into Cu 2 ZnSnS 4 induced slight negative shifts in binding energies and decreased the energy difference between the valence band and the Fermi level, while also enhancing crystallization, resulting in more uniform and compact structure. Furthermore, sample S2‐2% exhibited a significant enhancement of absorption value and electrical properties.