High-mobility flexible pentacene-based organic field-effect transistors with PMMA/PVP double gate insulator layers and the investigation on their mechanical flexibility and thermal stability

In this paper, we fabricated high performance flexible pentacene-based OFETs with low-k polymethylmethacrylate (PMMA, k = 3.5) and high-k dielectrics cross-linked poly(4-vinylphenol) (PVP, k = 4.1) as double gate insulator layers on poly(ethylene terephthalate) (PET) plastic substrate. The field-effect mobility (μ) of flexible pentacene-based OFETs was greatly increased from 0.66 cm² V^-1 s^-1 to 1.51 cm² V^-1 s^-1, meanwhile, their high electrical insulating properties were also well maintained which resulted in high ON/OFF current ratio of 10⁵. The control experiments showed that the high performance flexible OFETs were mainly attributed to the PMMA/PVP double dielectric layers which not only have high electrical insulating property but also favor the growth of pentacene films. The flexible OFETs still showed excellent mechanical flexibility when they were bent 1000 successive mechanical bending cycles and held under the bending state for 2 hours at a radius of 3.5 mm. In addition, the flexible OFETs also showed high thermal stability, which exhibited the mobility of 0.72 cm² V^-1 s^-1, the positive shift direction of V_TH, the ON/OFF current ratio of 10⁵ after heating to 100 °C for 2 hours in the atmosphere. Our results suggested that the PMMA/PVP double dielectric films were very suitable for the dielectric layer of the flexible OFETs.