1：Experimental Design and Method Selection

The heterojunctions were created by utilizing facing targets direct-current sputtering (FTDCS) at a pressure of 1.33 × 10?1 Pa. The photovoltaic properties were investigated through current density–voltage (J–V) curves under dark and illumination conditions, and capacitance–voltage (C–V) and conductance–voltage (G–V) characteristics were measured as a function of applied frequency.

2：Sample Selection and Data Sources

p-Type Si(111) substrates were used. The native oxide layer was removed, and i-Si and n-type NC-FeSi2 films were formed on the substrate by FTDCS using Si and FeSi2 targets, respectively.

3：List of Experimental Equipment and Materials

FTDCS system, Si and FeSi2 targets, palladium and aluminum for electrodes, X-ray diffraction (XRD) (Rigaku, RINT-2000/PC), dispersive Raman spectroscopy (Spectrometer Model: SENTERRA), Carl Zeiss Auriga Field Emission Scanning Electron Microscope (FESEM), precision LCR meter (Agilent, E4980A).

4：Experimental Procedures and Operational Workflow

The Si substrate was cleaned and set in the FTDCS system. An i-Si film was formed at 650°C, followed by an n-type NC-FeSi2 film at room temperature. Palladium and aluminum electrodes were formed using radio frequency magnetron sputtering. Structural, electrical, and photovoltaic properties were then characterized.

5：Data Analysis Methods

Series resistance (Rs) was estimated using the methods of Nicollian and Brews and Norde. Interface state density (Nss) was calculated using the Hill-Coleman method. XRD patterns were analyzed using the Scherrer equation to estimate crystallite size.