Solid-State Homojunction Electrochemical Transistors and Logic Gates on Plastic

Organic electrochemical transistors (OECTs) have attracted significant attention due to their unique ionic–electronic charge coupling, which holds promise for use in a variety of bioelectronics. However, the typical electronic components of OECTs, such as the rigid metal electrodes and aqueous electrolyte, have limited their application in solid-state bioelectronics that require design flexibility and a variety of form factors. Here, we demonstrated the fabrication of a solid-state homojunction OECT consisting of a pristine polymer semiconductor channel, doped polymer semiconductor electrodes, and a solid electrolyte. This structure combined the photo-crosslinking of all of the electronic OECT components with the selective doping of the polymer semiconductor. Three Lewis acids (AuCl₃, FeCl₃, and CuCl₂) were utilized as dopants for the metallization of the polymer semiconductor. The AuCl₃-doped polymer semiconductor with an electrical conductivity of ~100 S cm^-1 was successfully employed as the source, drain, and gate electrodes for the OECT, which exhibited a high carrier mobility of 3.4 cm² V^-1 s^-1 and excellent mechanical stability, with negligible degradation in device performance after 5000 cycles of folding at a radius of 0.1 mm. Homojunction OECTs were then successfully assembled to produce NOT, NAND, and NOR logic gates.