Study of the Mo thin films and Mo/CIGS interface properties

Molybdenum thin film is the under electrode used in chalcopyrite solar cells family (CuInSe2 and its alloys) because of the low resistivity of the Mo/CIS contact. During the solar cells process the Mo film is submitted to thermal and chemical constraints, therefore it should exhibits some specific properties to keep its mechanical and electrical properties. It is shown that the suitability of Mo films for such process depends strongly on the target-substrate distance and the argon pressure during deposition, i.e. to the internal constraints present in the films. Using an rf diode sputtering apparatus, adhesive films with small resistivity, rho = 40 mu Omega cm, can be achieved by modifying argon pressure during deposition. After co-evaporation of a Cu(In1-xGax)Se-2 film the chemical and electrical properties of the Cu(In1-xGax)Se-2/Mo interface have been studied. It is shown, by XPS depth profile, that MoSe2 is present at the interface. The contact resistivity rho(c) has been measured. Resistivities rho(c) < 0.08 Omega cm(2) were found. From these XPS and electrical measurements it appears that the MoSe2 interfacial layer mediates low resistivity Mo/CIGS contact. (c) 2004 Elsevier B.V. All rights reserved.