Controlling the Field-Effect Mobility of Regioregular Polythiophene by Changing the Molecular Weight


  • This work was supported in part by the National Science Foundation with a Graduate Research Fellowship, the MRSEC Program of the National Science Foundation under Award Number DMR-0213618, the Center for Integrated Systems at Stanford University, and by the US Department of Energy under grant DE-AC03-76SF00098.


A clear dependence of the hole mobility on molecular weight of poly(3-hexylthiophene) in films is demonstrated. The charge carrier mobility of regioregular polythiophene is shown to increase by four orders of magnitude as the molecular weight is increased from ∼3 200 g mol–1 to 36 000 g mol–1. These observations could explain why the mobility values obtained in different labs vary so widely and suggest that optimizing the molecular weight of conjugated polymers could lead to significant improvements in device performance.