Modulating Poly(methyl\nmethacrylate) Gate Dielectric\nBehavior with Cosolvent and Low-Temperature Processing for Low-Threshold-Voltage\nFlexible Organic Field-Effect Transistors

Low-power flexible electronic and bioelectronic applications\nare\nin substantial demand of low-threshold-voltage organic field-effect\ntransistors (OFETs). Detailed studies on surface and interfacial properties\nhave shown that the annealing temperature, dipole moment, and dielectric\nconstant of the processing solvents impact various device parameters\nsuch as the capacitance density, threshold voltage, stability, and\n density of charge trapping states. In this work, we achieved low-threshold-voltage\noperation in OFETs by employing a mixture of solvents comprising low\nand high dipole moments to process poly(methyl methacrylate) (PMMA).\nA blend with an optimized ratio of <i>t</i>-butyl alcohol\nand acetonitrile solvents was used to prepare the PMMA gate dielectric\nlayer. Both <i>t</i>-butyl alcohol and acetonitrile have\na boiling point of 82 °C, which implies a very low annealing\ntemperature to treat the PMMA films. This helps in realizing flexible\ndevices on unconventional substrates requiring low-temperature processing.\nThe devices fabricated on glass and flexible substrates yielded good\nelectrical performance, exhibiting a low threshold voltage of −3.5\n± 0.02 V, good bias stress stability, and mechanical flexibility.\nThrough a combination of experimental studies, we aim to provide insights\ninto how solvent choice influences the dielectric layer properties\nand the operation of OFETs. Therefore, our work demonstrates the efficacy\nand potential of a solvent engineering approach utilizing mixed solvents\nto treat PMMA as a gate dielectric layer, facilitating low-temperature\nand low-threshold-voltage flexible OFET devices.