Neutral solid polymer electrolyte for printed thin film transistors

The increased demand for lightweight wearable technology for health monitoring requires thin and flexible devices with low operation voltage to replace bulky conventional silicon-based rigid electronics. Neutral pH solid polymer electrolytes are promising alternatives to those traditional dielectric materials; the high dielectric constant of these aqueous based electrolytes enables the electrolyte gated field effect transistors (EGFETs) to operate at low voltage, while also facilitating integration into flexible and wearable devices. This study shows the integration of a solid polymer electrolyte with printed polymer semiconductor to create an EGFET device patterned on a flexible polymer substrate, in which the electrolyte forms a free standing, mechanically stable film. Electrical impedance spectroscopy (EIS) and cyclic voltammetry (CV) were used to assess the compatibility of the electrolyte with the polymer semiconductor and the gold electrodes. Fabricated EGFET devices with inkjet printed semiconductor and drop cast solid polymer electrolyte demonstrated good transistor behaviour with ~10³ ON/OFF ratio at < 1.2 V operation, with minimal performance degradation over at ambient condition for three days. The printability of the polymer semiconductor can further enable facile, high throughput fabrication of the EGFETs, while the flexible and lightweight nature of the substrate allows for integration with wearable electronics. Overall, the solid polymer electrolyte showed good integration with thin film transistors, with the potential to replace the conventional dielectrics in flexible and wearable electronics.