For potential new applications in photovoltaic, it is crucial to maintain the performance of organic solar cells (OSCs) on flexible substrates. The behavior of organic materials and stackings under stress (evolution of structure, strain, cracks,...) needs therefore to be carefully addressed. Our objective is to come to a better understanding of the relationship between the evolution of crystallinity and the mechanical behavior of semi-conducting polymer thin layers and stackings of OSC layers during mechanical loading. The structural properties of the individual photoactive materials as well as their properties when incorporated in a device stack i.e. surrounded by extraction layers, will be investigated by in situ Grazing Incidence XRD under applied uniaxial tensile stretching. This will allow a detailed understanding of the influence of materials fabrication, use of different extraction layers and nature of substrate on the mechanical strength of these organic layers.