High-Performance Organic Field-Effect Transistors Gated by Imidazolium-Based Ionic Liquids

Inducement of high charge carrier density in organic field-effect transistors (OFETs) is a subject of immense interest due to its fundamental and applied impact on device operation. Here, the high performance of imidazolium-based ionic liquid (IL)-gated OFETs is reported. By exploiting the p-doping of poly(3-hexylthiophene-2,5diyl) (P3HT) in the ambient environment and using the IL-gating, high charge carrier density (10(16) cm(-2)) has been induced in P3HT, which has resulted in high hole mobility (20.2 cm(2) V-1 s(-1)). This is a remarkable improvement in field-effect mobility in organic polymer semiconductors. Along with high mobility, low threshold voltage (similar to 0.6 V), low subthreshold swing (similar to 100 mV dec(-1)), and specifically the high transconductance (>1 mS) position this class of devices as a strong candidate for electrical sensor platforms. The compatibility of ILs with biomolecules and the direct access to IL/P3HT interface make these devices suitable for in situ biosensors. The IL components (cation and anion) were varied (one at a time) to investigate the effect on the electrical performance of the OFETs. An increase in the gate-electrode metal work function leads to a systematic decrease in the threshold voltage (by up to 0.6 V). The mobility exhibits a negative power dependence on specific capacitance, a signature of polaronic selflocalization in organic semiconductors. The shelf life of the IL-gated OFETs is found to be more than 40 days.

Automated summary

By utilizing imidazolium-based ionic liquid (IL) gating in organic field-effect transistors (OFETs), high charge carrier density and hole mobility in P3HT have been achieved, positioning these devices as potential candidates for electrical sensor platforms. The systematic variation of IL components and gate-electrode metal work function also provide insights into the electrical performance of the OFETs. Additionally, the long shelf life of IL-gated OFETs further enhances their practicality for various applications.