Na-doped Mo target sputtering for Cu(In,Ga)Se₂ thin film solar cells

This study employed a Mo-5 % Na thin film on a soda-lime glass substrate as the bottom layers of a Mo back contact using a sputtering process to achieve large area Cu(In,Ga)Se₂ (CIGS) cells application and uniform distribution. Our results demonstrate that increasing the ratio of Mo-5 % Na to Mo film thickness (R %) from 0 to 11 % enhanced the crystallinity of the deposited bi-layer Mo film, thereby increasing surface roughness and slightly reducing resistivity. Following selenization, optimal CIGS crystalline characteristics appeared when R % = 8 % (sodium content = 1.57 at.%), such that secondary phases were not generated, and the surface and depth distribution of sodium were uniform.