Manganese (Mn) doping effects on the structure and surface characteristics of copper zinc tin sulphide (CZTS) transition metal sulphides synthesised via a sol–gel method

Abstract

Transition metal sulphides have emerged as promising candidates for a range of electronic and energy-related applications owing to their tunable characteristics. This study investigates the effects of manganese (Mn)-doped copper zinc tin sulphide (Cu₂ZnSnS₄, CZTS) on its structural and surface properties. Mn-doped CZTS samples were synthesised via a sol–gel method at various doping percentages. The resulting samples were sulphurised prior to the physicochemical analyses. X-ray diffraction (XRD) confirmed the formation of a tetragonal phase, with noticeable lattice expansion due to Mn incorporation. The crystallite size increased from 24.52 nm to 42.01 nm at low Mn doping levels, while the degree of crystallinity decreased to 50–65%. Correspondingly, the strain and dislocation density were reduced to 3.32 × 10⁻³ rad and 0.57 × 10⁻³ (nm)⁻², respectively. Raman analysis verified a stannite-dominant structure, with red shifts corroborating the XRD findings. Although the surface areas and pore volume of CZTS samples decreased upon Mn doping, the pore size showed a notable increase. In addition, the particle size distribution ranged between 1 and 2 µm, and the zeta potential shifted from a net negative to a net positive charge, thereby enhancing the charge mobility after Mn doping. Scanning electron micrographs revealed reduced particle agglomeration, improved grain size, and surface uniformity following Mn doping, while energy-dispersive X-ray analysis confirmed the successful Mn substitution into the CZTS in all samples. In conclusion, Mn doping effectively modified the lattice structure and surface characteristics of CZTS, indicating its potential to improve the material's performance in electronic devices, energy storage, and energy harvesting applications.