Discriminating bulk, surface and interface aging effects in polymer-based active materials for efficient photovoltaic devices

► Structural/morphological properties of bulk heterojunctions for OPVs were studied ► X-ray and AFM techniques were applied in situ up-on illumination ► The meso-scale modifications of the P3HT:PCBM blends were observed directly ► The study allowed to discriminate among bulk, surface and interface aging effects.