Inkjet‐Printed Ternary Oxide Dielectric and Doped Interface Layer for Metal‐Oxide Thin‐Film Transistors with Low Voltage Operation

Additive solution process patterning, such as inkjet printing, is desirable for high‐throughput roll‐to‐roll and sheet fabrication environments of electronics manufacturing because it can help to reduce cost by conserving active materials and circumventing multistep processing. This paper reports inkjet printing of YxAl2−xO3 gate dielectric, In2O3 semiconductor, and a polyethyleneimine‐doped In2O3 interfacial charge injection layer to achieve a thin‐film transistor (TFT) mobility (μsat) of ≈1 cm2 V−1 s−1 at a low 3 V operating voltage. When the dielectric material is annealed at 350 °C, plasma treatment induces low‐frequency capacitance instability, leading to overestimation of mobility. On the contrary, films annealed at 500 °C show stable capacitance from 1 MHz down to 0.1 Hz. This result highlights the importance of low‐frequency capacitance characterization of solution‐processed dielectrics, especially if plasma treatment is applied before subsequent processing steps. This study progresses metal‐oxide TFT fabrication toward fully inkjet‐printed thin‐film electronics. Low‐cost additive processes such as inkjet printing offer a viable fabrication route for active components such as metal‐oxide thin‐film transistors (TFTs). The effect of O2 plasma, a typical means to improve wetting of the inks, is investigated on the gate dielectric. Finally, TFTs are demonstrated with inkjet‐printed In2O3 semiconductor, YxAl2−xO3 gate dielectric, and polyethyleneimine‐doped In2O3 charge injection layer.