Formation of Large Crystalline Domains in a Semiconducting Polymer with Semi-fluorinated Alkyl Side Chains and Application to High-Performance Thin-Film Transistors

The semi-fluorinated alkyl (SFA) side chain introduced thienylenevinylene (TV)-based p-type polymer, PC12TVC5F7T, was synthesized for use in organic thin-film transistors (OTFTs). Herein, we investigated the influence of SFA side chains on the morphology, molecular orientation, and crystalline structure using a combination of atomic force microscopy (AFM), scanning electron microscopy (SEM), two-dimensional (2D) grazing-incidence wide-angle X-ray scattering (GIWAXS), and density functional theory (DFT) calculations. Interestingly, the incorporation of SFA side chains led to the evolution of plate-like large-sized domains and also strongly intermolecular stacked high crystalline structures. Furthermore, due to the strong interactions between SFA side chains, several (00h) peaks could be observed for PC12TVC5F7T, in spite of their fairly large dihedral angle. As a result, due to the well-developed microstructure of PC12TVC5F7T, the OTFT devices based on it exhibited a high hole mobility of 1.91 cm2 V-1 s-1, which is an outstanding value among the poly(thiophene) derivative polymers. These observations indicate that large-sized domains and strongly intermolecular stacked high crystalline structures, which are beneficial for charge carrier transport, could be attained by the introduction of SFA side chains, further enhancing the performance of the OTFTs.