1：Experimental Design and Method Selection:

The study employed electrochemical atomic layer deposition (E-ALD) for layer-by-layer growth of CIGS and CdS thin films on Mo foil substrates. The method is based on underpotential deposition (UPD) principles, using surface-limited reactions in solution phase. Cyclic voltammetry (CV) was used to determine UPD potentials for each element.

2：Sample Selection and Data Sources:

Mo foil (Alfa Aesar) was used as the substrate. Electrolyte solutions were prepared using chemicals from Sigma-Aldrich and Samchun Chemicals. Samples included CIGS films with different superlattice periods (50, 100, 150, 200 SP) and CdS layers (70 periods) deposited on them.

3：List of Experimental Equipment and Materials:

Equipment included a potentiostat (Model PSAT6212-7), electrochemical cell, Ag/AgCl reference electrode, gold wire counter electrode, X-ray diffractometer (Rigaku D/MAX 2200), SEM (Jeol/JSM-5600), EDS (Bruker 410-M), potentiostat/galvanostat (Autolab PGSTAT302N), and Xe lamp (Oriel, 150 W). Materials included Mo foil, various sulfate and sulfide salts, and deionized water.

4：Experimental Procedures and Operational Workflow:

For CIGS deposition, UPD potentials were applied in sequences (e.g., 2InSe/2GaSe/1CuSe) with specific deposition times. For CdS deposition, cycles of Cd and S deposition were performed. Solutions were flowed into the cell, purged with Ar, and controlled via LABVIEW software. Characterization involved XRD, SEM, EDS, and PEC measurements.

5：Data Analysis Methods:

XRD patterns were compared to JCPDS files, SEM images analyzed surface morphology, EDS provided atomic composition, and PEC data interpreted semiconductor type from photocurrent responses.