PffBT4T-2OD (PCE11) is a low band-gap (1.65 eV) semiconducting polymer for organic photovoltaics (OPVs), which has reached power conversion efficiencies (PCEs) approaching 11% . These efficiencies are a result of the high crystallinity of the polymer, providing excellent hole transport mobilities on the order of 10-2 cm2V-1s-1, and the ability to use a thick active layer, resulting in improved light absorption.