PffBT4T-2OD is one of the most recent and most successful low bandgap conjugated polymers used in organic photovoltaics - PffBT4T-2OD based OPV devices have power conversion efficiencies PCE~10%. However, and contrary to other bulk-heterojunction systems based on polymers such as P3HT and PCDTBT which show their best PCE values when the thickness of the active BHJ layer is ~100nm, OPV devices based on PffBT4T-2OD show their maximum PCEs when the active layer thickness is ~300nm. This particular property of PffBT4T-2OD based devices has been attributed to the fact that PffBT4T-2OD exhibits higher crystallinity which most likely confers it a higher hole-mobility than that observed in other conjugated polymers. However, as far as we know, the measurement of the charge mobility of PffBT4T-2OD is still unreported on the literature. In this project we propose to measure it using muons.