High-energy sputtering for the deposition of a conductive and adherent single molybdenum layer for solar cell applications

Abstract

Molybdenum (Mo) thin films are thought to be an excellent back contact for CuIn1-xGaxSe2 (CIGS) solar cells. Mo films require high conductivity and good adhesion to glass substrates; however, these characteristics cannot be combined in sputtered Mo under the same deposition conditions. Direct current Magnetron Sputtering (DcMS) and High-Power Impulse Magnetron Sputtering (HiPIMS) were used to deposit Mo films on glass substrates, and the effects of working pressure and substrate bias on their characteristics were investigated. To begin, single layers of Mo were produced at pressures ranging from 0.2 to 1.4 Pa. The Mo films deposited at the lowest working pressure of 0.2 Pa were then subjected to a negative substrate bias varying from -50 to -200 V. All of the HiPIMS films adhered well to the glass substrate, whereas the DcMS films deposited at various pressures showed poor adhesion. Furthermore, our findings demonstrated that applying a negative substrate bias reduced the resistivity of Mo films to the lowest values of 2.56 × 10−5 Ω.cm and 2.771 × 10−5 Ω.cm, respectively, for the HiPIMS and DcMS-deposited films, while improving the adhesion of the DcMS-samples due to the development of films with homogenous stress distribution.