Difluorobenzoxadiazole‐Based Polymer Semiconductors for High‐Performance Organic Thin‐Film Transistors with Tunable Charge Carrier Polarity

Abstract

AbstractA series of difluorobenzoxadiazole‐based copolymers are synthesized for applications in high‐performance organic thin‐film transistors. Four π‐spacers with distinct electrical properties, bithiophene, difluorobithiophene, 2‐thiophene‐2′‐thiazole, and bithiazole, are inserted between head‐to‐head linkage containing bithiophene to promote polymer chain packing. Among the series, polymer containing bithiophene exhibits a unipolar p‐channel performance with a substantial hole mobility of 2.92 cm2 V−1 s−1, and minor structural modification leads to polymer containing bithiazole showing a remarkable unipolar n‐channel performance with an electron mobility of 0.83 cm2 V−1 s−1. Through a simple structural modification, such a drastic charge carrier polarity change without sacrificing mobility is elusive in organic thin‐film transistor field. Polymer containing hybrid 2‐thiophene‐2′‐thiazole spacer exhibits ambipolarity with encouraging hole/electron mobility of 0.27/0.35 cm2 V−1 s−1, and polymer containing difluorobithiophene shows an average hole mobility of 0.53 cm2 V−1 s−1. Among the results, p‐channel transistors exhibit encouraging device stability. The results demonstrate that difluorobenzoxadiazole is a versatile building block for enabling high‐mobility semiconductors with variable charge carrier polarity. X‐ray diffraction reveals that all difluorobenzoxadiazole‐based polymers have substantial film crystallinity with close π‐stacking and varied polymer chain orientation. The structure–property–device performance correlations from this study offer useful insights for materials innovation in organic thin‐film transistors.