Molybdenum thin films are widely used as back contact for CIGS-based solar cells. In this paper, the properties of Mo layers deposited by DC and RF sputtering are investigated in view of a specific optimization of electrodeposited CIGS solar cells. In the first part of the paper RF and DC films are grown on soda lime glass, in a pressure range from 2 to 20 mTorr, and for various RF power and DC current. They are then characterized by optical, electrical and structural methods. It appears that the films deposited by RF mode sputtering are more reflective, conductive and adherent than those obtained by DC mode. Structurally, they present different behaviors with respect to nucleation and growth of CIGS precursor layers by electrodeposition. A large difference is observed in the photovoltaic properties of completed cells, with much better performances obtained with DC Mo layers. (C) 2010 Elsevier B.V. All rights reserved.