Engineering Intrinsic Flexibility in Polycrystalline Molecular Semiconductor Films by Grain Boundary Plasticization.

Mechanically flexible films of the highly crystalline core-cyanated perylenediimide (PDIF-CN2) molecular semiconductor are achieved via a novel grain boundary plasticization strategy in which a specially designed polymeric binder (PB) is used to connect crystallites at the grain boundaries. The new PB has a naphthalenediimide-dithiophene π-conjugated backbone end-functionalized with PDI units. In contrast to conventional polymer-small molecule blends where distinct phase separation occurs, this blend film with plasticized grain boundaries exhibits a morphology typical of homogeneous PDIF-CN2 films which is preserved upon bending at radii as small as 2 mm. Thin-film transistors fabricated with PB/PDIF-CN2 blends exhibit substantial electron mobilities even after repeated bending. This design represents a new approach to realizing flexible and textured semiconducting π-electron films with good mechanical and charge transport properties.