Cyanostyrylthiophene-Based Ambipolar Conjugated Polymers: Synthesis, Properties, and Analyses of Backbone Fluorination Effect

Herein, we report the synthesis and characterization of a series of ambipolar cyanostyryl­thiophene (CST)-based conjugated polymers without or with fluorine substituents, namely PD-CST, PD-3F-CST, PD-23F-CST, and PD-25F-CST. With the change of the number or incorporating position of fluorine substitutes on the novel CST unit, the electron mobilities of field-effect transistors based on these polymers dramatically increased from 0.0015 cm2 V–1 s–1 for PD-CST, 0.13 cm2 V–1 s–1 for PD-3F-CST, and 0.25 cm2 V–1 s–1 for PD-23F-CST to 0.53 cm2 V–1 s–1 for PD-25F-CST. AFM and GIXRD investigation indicated that the annealed PD-25F-CST thin film possesses stronger crystallization tendency and highly ordered lamellar packing than those of the other polymers. Further theoretical calculations and single-crystal X-ray diffraction analysis deeply revealed the remarkable influences of the number and incorporating position of fluorine substitutes on the frontier orbital energy levels, backbone conformation, and charge transport properties of polymer semiconductors.