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

Abstract

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 S₂O₃²⁻, 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.