Electrodeposition of Cu₂NiSnS₄ absorber layer on FTO substrate for solar cell applications

Potentiostatic and in situ electrochemical impedance spectroscopy (EIS) measurements were recorded to study the nucleation and growth mechanisms of electrodeposited Cu₂NiSnS₄ (CNTS) thin films from aqueous solution at different applied potentials. The electrodeposition process of Cu-Ni-Sn-S precursors were studied using cyclic voltammetry and chronoamperometry techniques. The nucleation and growth mechanism of these films was found to follow a three-dimensional progressive nucleation limited by diffusion-controlled growth. The nucleation mechanism is found to be influenced by the presence of S₂O₃ ^2-, which prompts the electrodeposition of S. In situ electrochemical impedance spectroscopy (EIS) investigates the electrodeposition behavior of CNTS precursors on the surface electrode. A capacitive behavior was observed at high frequencies, while the presence of Warburg diffusion was detected only for potentials less negative than -1.0 V vs. Ag/AgCl. The crystallographic structure, morphology, composition, and optical band gap of CNTS thin films was examined using X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and UV-visible spectroscopy. Electrodeposition at -0.98 V vs. Ag/AgCl resulted in the formation of microsheets with a uniform morphology and homogeneous thickness of sulfurized CNTS film. This potential also proved to be optimal for achieving higher crystallinity, a pure phase, and a suitable band gap energy of approximately 1.6 eV.