Organic molecules are assembled together by weak non-covalent intermolecular interactions in solid state. Multiple crystalline packing states (crystal polymorphism) have commonly existed in the active layer for organic field-effect transistors (OFETs). Different polymorphs, even with the slightest changes in their molecular packing, can differ the charge transport mobility by orders of magnitude. Therefore, accessing new polymorphs can serve as a novel design strategy for attaining high device performance. Here, we review the state of the art in this emerging field of crystal polymorph control. We firstly introduce the role of polymorphism and the methods of polymorph control in organic semiconductors. Then we review the latest studies on the performance of polymorphs in OFET devices. Finally, we discuss the advantages and challenges for polymorphism as a platform for the study of the relationship between molecular packing and charge transport.
Part of the book: Integrated Circuits/Microchips