Method for increasing the photoconductive response in conjugated polymer/fullerene composites

The authors poly(3-hexylthiophene)/[6,6]-phenyl C61-butyric acid methyl ester present a technique for modifying the internal structure of bulk heterojunction films which yields significantly improved photoconductivity. This method comprises the addition of alkyl thiol molecules to the polymer/fullerene solution prior to spin coating. Based on the steady-state and transient photoconductivity measurements, the photoresponsivity is an order of magnitude greater than that in films spun from pristine solvent; additionally, the carrier mobility measurements indicate significant increase in the hole mobility, consistent with the enhanced structural order inferred from x-ray diffraction and optical absorption measurements.