The traditional electrochemical deposition process used to prepare Cu(In, Ga)Se2 (CIGS) thin films has inherent flaws, such as the tendency to produce low-conductivity Ga2O3 phase and internal defects. In this article, CIGS thin films were prepared under vacuum (3 kPa), and the mechanism of vacuum electrodeposition CIGS was illustrated. The route of Ga incorporation into the thin films could be controlled in a vacuum environment via inhibiting pH changes at the cathode region. Through the incorporation of a low-conductivity secondary phase, Ga2O3 was inhibited at 3 kPa, as shown by Raman and X-ray photoelectron spectroscopy. The preparation process used a higher current density and a lower diffusion impedance and charge transfer impedance. The films that were produced had larger particle sizes.
