High Performance, Flexible, and Thermally Stable All-Solid-State Organic Electrochemical Transistor Based on Thermoplastic Polyurethane Ion Gel

Organic electrochemical transistors (OECTs) are a generation of transistors with high transconductance, where the whole volume of the semiconducting channel is involved in the electrochemical doping process. However, the use of liquid electrolytes limits the application of OECTs, and the doping process is also complicated due to the presence of water in the electrolyte. In this study, thermoplastic polyurethane (TPU)-based solid electrolyte was used in OECTs for the first time. Three types of ionic liquids were blended with a TPU polymer matrix as a solid electrolyte and investigated on the OECTs based on three kinds of p-type conjugated semiconductors. An in situ spectrochemistry study was further carried out to confirm the doping/dedoping process of these conjugated semiconductors by the TPU-based solid electrolyte. The robustness and high stability of the fabricated solid-state OECTs (SSOECTs) were demonstrated through continuously applied bias, long time operation under ambient conditions, and varying temperatures (-50 to 120 degrees C). Highly flexible SSOECTs were also obtained on a polyethylene terephthalate (PET) substrate, which showed negligible fluctuation in on/off-current (Ion/Ioff) after 1000 cycles of bending. Based on these high performing SSOECTs, inverter circuits were fabricated in both unipolar and complementary configurations, where n-type and p-type OECT-based complementary inverters showed a higher gain (46) compared with that of the unipolar design.

Automated summary

In this study, thermoplastic polyurethane (TPU)-based solid electrolyte was used for the first time in organic electrochemical transistors (OECTs). Three types of ionic liquids were blended with TPU polymer matrix as a solid electrolyte for OECTs based on different p-type conjugated semiconductors. The doping/dedoping process of these conjugated semiconductors by TPU-based solid electrolyte was confirmed through in situ spectrochemistry study. The fabricated solid-state OECTs (SSOECTs) showed high stability under continuously applied bias, long time operation, and varying temperatures, and highly flexible SSOECTs were obtained on a polyethylene terephthalate (PET) substrate with negligible fluctuations in on/off-current (Ion/Ioff) after 1000 bending cycles. Based on these high performing SSOECTs, inverter circuits were fabricated with higher gain in complementary configurations.