Synthesis and Performance of Bithiophene Isoindigo Organic Semiconductors with Side‐Chain Functionality in Transistors

The isoindigo and its derivatives have rapidly garnered attention as widely employed electron‐deficient moieties, finding extensive applications in organic field‐effect transistors. In this study, four different isoindigo‐based organic semiconductor polymers were synthesized via a Stille coupling reaction of four isoindigo molecules with varying side chains serving as acceptors and bithiophene as donors. Furthermore, their optical, electrochemical, thermal stability, and other relevant properties were comprehensively evaluated. These polymers exhibited remarkable electrochemical and thermal stability attributed to their low LUMO energy level, which facilitates effective electrical contact between the semiconductor layer and the source/drain while ensuring excellent air stability for the semiconductor polymers. Additionally, solution‐gate field‐effect transistors prepared using these polymers achieved hole mobilities of 10⁻² cm² V⁻¹ S⁻¹ along with an I_on/I_off ratio of 8.39×10³, demonstrating exceptional field‐effect performance.