Rapid thermal sulfurization of metallic precursors has proven to be a successful method for the preparation of Cu(In,Ga)S-2 based solar cells. However, during the sulfurization, several problems can be encountered. Due to the difference in reaction rates between ternary sulfides, the process can result in absorbers with a layered CuInS2/CuGaS2 structure or slow and incomplete sulfurization that leads to samples where an unreacted Cu-Ga metallic phase remains at the back of the sample. The formation kinetics of single phase Cu(In,Ga)S-2 is a complex process which depends on several parameters. In this work, we focus on the influence of precursor stacking and investigate the growth of Cu(In,Ga)S-2 thin films using scanning electron microscopy and X-ray diffraction. It is observed that precursor alloying occurs prior to sulfurization and that the Cu(In,Ga)S-2 compound is formed by the interdiffusion of the ternary CuInS2 and CuGaS2 phases. Correlation between the structural properties of the precursors/absorbers and the obtained solar cells is made. (C) 2011 Elsevier B.V. All rights reserved.