Organic photovoltaics (OPVs) are a low cost alternative to existing photovoltaic materials. The efficiency of OPVs is steadily increasing towards the point where their cost per Watt is competitive. In order to improve the efficiency of such devices further it is essential to control the nanoscopic morphology of the films being fabricated. Blends of P3HT(poly 3-hexyl thiophene):PCBM([6,6]-phenyl C61 butyric acid methyl ester) are the current standard materials used to fabricate this type of solar cell, and as such are the focus of a huge research effort. However the morphology of the PCBM aggregates within the active layer is still not well understood. Therefore, we propose to use GISANS to study the P3HT & PCBM material system and thereby determine the nanostructure of the PCBM aggregates within the active layer of the devices.