Structural origin of gap states in semicrystalline polymers and the implications for charge transport

Abstract

We quantify the degree of disorder in the π-π stacking direction of crystallites of a high performing semicrystalline semiconducting polymer with advanced X-ray lineshape analysis. Using first principles calculations, we obtain the density of states of a system of π-π stacked polymer chains with increasing amounts of paracrystalline disorder. We find that for an aligned film of PBTTT the paracrystalline disorder is 7.3%. This type of disorder induces a tail of trap states with a breadth of ~100 meV as determined through calculation. This finding agrees with previous device modeling and provides physical justification for the mobility edge model.

Text and figures are unchanged in the new version of the file. The only modification is the addition of a funding source to the acknowledgments