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 electrolytes, have limited their application in solid-state bioelectronics that requires design flexibility and a variety of form factors. Here, the fabrication of a solid-state homojunction OECT consisting of a pristine polymer semiconductor channel, doped polymer semiconductor electrodes, and a solid electrolyte is demonstrated. This structure combines the photo-crosslinking of all of the electronic OECT components with the selective doping of the polymer semiconductor. Three Lewis acids (gold (III) chloride (AuCl₃), iron (III) chloride (FeCl₃), and copper (II) chloride (CuCl₂)) are utilized as dopants for the metallization of the polymer semiconductor. The AuCl₃-doped polymer semiconductor with an electrical conductivity of ≈100 S cm⁻¹ is 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 are then successfully assembled to produce NOT, NAND, and NOR logic gates.