1：Experimental Design and Method Selection:

The study involved the deposition of ultrathin TaN intermediate layers (IL) with thicknesses from 3 nm to 12 nm on Mo films, followed by the deposition of CZTS films using RF sputtering from a non-stoichiometric Cu

2：69ZnSnS4 quaternary target. The samples were then annealed in the presence of elemental S vapor and Ar at 600°C for 10 min. Sample Selection and Data Sources:

Soda-lime glass (SLG) substrates were used for the deposition of Mo back electrode, TaN IL, and CZTS films.

3：List of Experimental Equipment and Materials:

A Denton Discovery-18 sputtering system was used for Mo and TaN deposition, and a Bruker D8 general area detector X-ray diffraction (XRD) system for crystal quality characterization. Other equipment included a Raman measurement system, XPS system, TOFSIMS system, and STEM for detailed analysis.

4：Experimental Procedures and Operational Workflow:

After deposition, the samples were characterized using various techniques to study their morphology, chemical and structural properties, and elemental composition before and after sulphurization.

5：Data Analysis Methods:

The data obtained from the various characterization techniques were analyzed to understand the effect of TaN IL on the interfacial reaction between CZTS and Mo, and the diffusion of S into Mo.