Binary polymer composite dielectrics for flexible low-voltage organic field-effect transistors

Insulating polymers have been recognized as a promising class of gate dielectrics for organic field-effect transistors (OFETs). However, the relative permittivity of most single polymer dielectrics is quite fixed and too low to afford low-operating voltages of OFETs. For flexible low-voltage OFETs, dielectric tunable polymer composites are highly desirable. Here, a new type of binary polymer composite dielectrics is developed by incorporating a small amount of polyacrylic acid (PAA) into poly(methyl methacrylate) (PMMA) to reduce the operating voltage and enhance the device performance. The resulting dielectric layers deliver a tunable relative permittivity from 3.32 to 4.28 with an increase of PAA contents in the composite. As results, flexible OFETs using PMMA: PAA dielectrics show greatly improved mobility and reduced threshold voltages with a low-operating voltage below -5 V. The OFETs using the composite dielectric also exhibit excellent performance stability during mechanical bending tests with different radii, where the mobility can maintain 95% of its initial value over 5000 cycles under a bending radius of 5 mm. The tunable dielectric properties and high robustness of these novel dielectrics make them promising candidates for solution-processed low-voltage flexible OFETs with low power consumption.