Organic photovoltaic (OPV) materials must meet some stringent technological requirements, to bear continuous operation under variable temperature conditions. Here, an original approach to control the degradation pathway associated to the active material morphological instability is proposed. We demonstrate, for the first time, that polymer-fullerene nanostructured films incorporating poly(3-hexylthiophene) nanofibers, obtained from concentrated solutions at room-temperature, are characterized by superior structural durability. This is obtained monitoring in situ the active layer bulk/interface morphological properties by joint energy dispersive X-ray and atomic force microscopy time-resolved techniques: the preservation of the nanoscale morphology of the pristine films is very promising for flexible OPV applications. (C) 2013 Elsevier B. V. All rights reserved.