Methyl functionalization on polyimide side chains as gate dielectrics for organic transistors

Among a wide variety of polymer-based dielectric materials, aromatic polyimide (PI) and its derivatives have garnered significant attention as gate dielectrics for use in organic thin-film transistors (OTFTs) due to their flexibility, large-area processability, high-temperature resistance, and cost-effectiveness. In this work, we utilized a structure fine-tuning manner by incorporating different amounts of methyl groups into the PI backbone. Two solution-processable aromatic PI-derived materials were prepared using the low-temperature chemical imidization method, and they displayed good film-forming properties, excellent thermal stability, low leakage current density, and low dielectric loss, providing a solid foundation for their use as OTFT gate dielectric layers. As a proof of concept, we utilized these two PI-derived dielectric layers for application in para-sexiphenyl (p-6P)/vanadyl-phthalocyanine (VOPc) TFT devices. Compared to the pristine PI without methyl groups, the mobility and threshold voltage of the OTFT based on PI containing different amounts of methyl groups as dielectric layers have been significantly improved. The strategy of methyl functionalization on PI side chains reported in this work may offer new possibilities for achieving high mobility and low threshold voltage in OTFTs. The strategy of methyl functionalization on polyimide side chains may offer new possibilities for achieving high mobility and low threshold voltage in organic thin-film transistors.