High-k Gate Dielectrics for Organic Field-Effect Transistors: Interfacial Engineering, Performance Optimization, and...

Organic field-effect transistors (OFETs) are promising platforms for flexible, wearable, biointegrated, and large-area electronics owing to their mechanical compliance, solution processability, low-temperature fabrication, and molecular tunability. However, their practical application requires low-voltage operation, low power consumption, high operational stability, and scalable manufacturing, which are strongly influenced by the gate dielectric and its interface with the organic semiconductor. High-k gate dielectrics can increase gate capacitance and enhance electrostatic control, enabling low-voltage operation. However, a higher dielectric constant does not necessarily lead to better device performance, as strong polarization, surface polarity, interfacial trapping, dipolardisorder, remote phonon scattering, leakage, ion migration, and dielectric-semiconductor incompatibility can impair charge transport and device reliability. This Review presents a performance-oriented and interface-centered overview of high-k gate dielectrics for OFETs. We first classify high-k dielectric systems into inorganic oxides, molecularly engineered polymers, organic-inorganic hybrids and composites, and all-organic composite/multilayer structures, highlighting their polarization mechanisms, advantages, limitations, and structure-property relationships. We then discuss how dielectric properties and interfaces affect carrier mobility, threshold voltage, switching characteristics, charge injection, leakage current, hysteresis, and operational stability. Particular attention is given to interface engineering strategies, including surface modification, buffer layers, multilayer architectures, molecular design, composite construction, and defect/passivation control. We further discuss long-term reliability under electrical, thermal, mechanical, and environmental stresses, as well as emerging dielectric systems, low-temperature and scalable fabrication, large-area uniformity, process integration, and commercialization challenges. Finally, we summarize key design considerations for balancing high capacitance, low leakage, interfacial compatibility, mechanical robustness, environmental stability, and scalable processability. By integrating dielectric design, interface engineering, device physics, reliability, and manufacturing, this Review provides guidelines for developing low-voltage, stable, and scalable OFETs for next-generation flexible electronics.