Effects of molecular weight on the electrical properties of electrochemically synthesized poly(3-hexylthiophene)

Abstract The relation between molecular weights and electrical properties was investigated for electrochemically prepared poly(3-hexylthiophene) (PHT). The PHT films with weight-average molecular weight ( M w ) in the range 12 500–58 000 were prepared by controlling the polyerization conditions. For M w −1 to 10 1 S cm −1 with increasing M w . For M w > 25 000, the increase in σ with M w was minor. The visible absorption maximum ( π−π∗ absorption band) of the neutral PHT films shifted to the red side as M w increased. The shift was more prominent in the samples with low M w ( M w resulted in an increase in regularity of supermolecular structure in the as-polymerized PHT films, which enhanced the development of a π-conjugated system in the sample.