Synthesis and characterization of photoactive material Cu₂NiSnS₄ thin films

In this work, we fabricated photoactive material copper–nickel–tin–sulphide Cu₂NiSnS₄ (CNTS) thin films on indium-doped tin oxide (ITO) coated glass substrates via an easy electrodeposition technique. The CNTS films have been characterized by different methods such as X-ray diffraction (XRD), Raman spectroscopy, atomic force microscopy (AFM), UV–vis spectrophotometer, electrochemical impedance spectroscopy (EIS) and Hall effect measurements. Both XRD patterns and Raman spectra confirmed the formation of a polycrystalline CNTS single phase without any secondary phases. AFM studies of the CNTS samples showed that morphology depends on the electrodeposition time. It was also found that the optical band gap redshifts from 1.74 to 1.52 eV as the film thickness rises from 450 to 1560 nm. The Nyquist plots obtained from EIS of the planar junction CNTS/electrolyte showed the existence of one semicircle, which was modeled by an equivalent electrical circuit thanks to the Randles model. The best photocathode for PEC water splitting was obtained for the sample with the optimized thickness of 1250 nm. From Hall effect measurement, it is inferred that the CNTS thin films of thickness 1250 nm have a positive Hall coefficient (R_H), carrier’s density ~ 2.9 × 10¹⁶ cm⁻³, Hall mobility ~ 120 cm² V⁻¹ s⁻¹ and electrical resistivity ~ 0.54 Ω cm.