Solution-Processed Titanium Dioxide Ion-Gated Transistors and Their Application for pH Sensing

Titanium dioxide (TiO₂) is an abundant metal oxide, widely used in food industry, cosmetics, medicine, water treatment and electronic devices. TiO₂ is of interest for next-generation indium-free thin-film transistors and ion-gated transistors due to its tunable optoelectronic properties, ambient stability, and solution processability. In this work, we fabricated TiO₂ films using a wet chemical approach and demonstrated their transistor behavior with room temperature ionic liquids and aqueous electrolytes. In addition, we demonstrated the pH sensing behavior of the TiO2 IGTs with a sensitivity of ~48 mV/pH. Furthermore, we demonstrated a low temperature (120°C), solution processed TiO2-based IGTs on flexible polyethylene terephthalate (PET) substrates, which were stable under moderate tensile bending.