Properties of the Mo Back Contact for the Formation of a Thin-Film Photovoltaic Absorber

A Taguchi experimental design was used to find which deposition parameter has the most dominant effect on the electrical resistivity of molybdenum (Mo) films. Based on the most important parameter, the Mo films were further characterized by structural, electrical, and adhesive methods. Then, a copper indium gallium selenide (CIGS) thin film was fabricated by a two-stage process on the obtained Mo layer. The results show that working pressure had a dominant effect on electrical resistivity. The Mo films deposited at 1 mTorr and 2 mTorr exhibited compressive strain and dense polycrystalline microstructure, whereas those deposited at 3 mTorr and 4 mTorr exhibited tensile strain and an elongated grain with open boundaries. A Mo film with open porous structure, tensile strain, and lower resistivity was suitable for the formation of CIGS films. After selenization at 560°C, a single-phase chalcopyrite CIGS film with a layer of MoSe 2 at the Mo/CIGS interface was obtained.