Enhancement of Out‐of‐Plane Hole Mobility in Poly(3‐Hexylthiophene)‐b‐Poly(styrene) Film

Two or three orders of higher magnitude out‐of‐plane hole mobilities are observed in the films of poly(3‐hexylthiophene)‐b‐poly(styrene) (P3HT‐b‐PSt) compared with those of P3HT fabricated with the same conditions in a diode geometry. From grazing incidence wide angle X‐ray diffraction analysis, it is found that there is a trend that PSt domains hinder the growth of alkyl stacking, and promote that of the π–π stacking. Differential scanning calorimetry thermogram of P3HT‐b‐PSt exhibits distinct double endothermic peaks, and double glass transitions. The larger change of heat capacity in glass transition at higher temperature indicates that the larger content of rigid amorphous region exists compared with P3HT. It is considered that the higher content of rigid amorphous domain (short‐range ordered packing) interconnects the crystallites (long‐range ordered packing) leading to the extraordinary higher mobility in P3HT‐b‐PSt film. Block copolymers consisting of poly(3‐hexylthiophene) and poly(styrene) films exhibit two or three orders of higher magnitude out of plane mobilities compared with those of P3HT homopolymer. The results ascribe the enhanced mobilities in the block copolymers mainly to the interconnection of crystallites via rich rigid amorphous domains as well as the improvement of π–π stacking in the “face‐on” crystallites.