Nanoscale Flexible Pentacene-Based Organic Field-Effect Transistors with Triple PMMA/SiO₂/ZnO Gate Insulator Layers

Nanoscale pentacene-based organic field-effect transistors (OFETs) incorporating a triple insulating layer of polymethyl methacrylate (PMMA), silicon dioxide (SiO2), and zinc ox-ide (ZnO) were successfully fabricated on glass and flexible PET substrates. The insulating layers significantly enhanced device performance, with the OFETs achieving field-effect mobility (µ) values more than twice as high as those reported in the literature. Specifically, mobility of ~6.75 cm²/V·s on glass, ~7.141 cm²/V·s on flexible substrates (before bending), and ~6.88 cm²/V·s (after bending) were observed. Threshold voltages (Vth) of -7 V and -9 V were estimated for the flexible OFETs before and after bending, respectively, alongside a high on/off current ratio exceeding 10³ for all devices. Minimal hysteresis in the transfer and output characteristics indicated excellent, trap-free interaction between the insulating layers and the pentacene. The high dielectric constant of the PMMA/SiO2/ZnO triple insu-lating layers was identified as a critical factor driving the exceptional performance, stabil-ity, and low hysteresis of the OFETs. These results underscore the pivotal role of advanced insulating layers in optimizing OFET performance and durability.