A CdTe/CdS heterostructure was fabricated on Fluorine Tin Oxide glass to produce thin-film photovoltaic devices. A CdCl2 layer was deposited onto the CdTe absorber layer and the subsequent annealing of the stack was performed in a He atmosphere. The influence of the CdCl2-activation step on the interfaces was investigated by monitoring the phase transition of CdCl2-heat-treated CdTe specimens during temperature ramp annealing via in situ high-temperature X-ray diffraction. X-ray Photoelectron Spectroscopy depth profiling data confirmed the interdiffusion between the CdTe and CdS layers through observation of the binding energy shifts and atomic ratio. The experimental results reveal that a compressive force, which is due to the formation of CdTe-CdCl2 eutectic liquid phases between grains, which cause the capillary action of such liquid phases, seems to introduce a compressive strain in the plane of the film that facilitates the recrystallization process. (C) 2012 Elsevier B.V. All rights reserved.