Recent Progress on High‐Capacitance Polymer Gate Dielectrics for Flexible Low‐Voltage Transistors

Abstract

The gate dielectric layer is an essential element of field‐effect transistors (FETs), large area integrated circuits, and various application electronics. Beyond basic insulation between the semiconductor layer and gate electrode, FET performance largely depends on the capacitance of the chosen insulator layer properties. Recent functional devices developments require new functionalities, such as high mechanical flexibility and stretchability in addition to basic insulating and physical properties. This review focuses on recent developments of high‐capacitance polymer gate dielectric materials and their application for low‐voltage flexible FETs. The fundamental principles and components of transistors are discussed briefly, then the underlying concepts for gate dielectrics and the mechanisms for polymer dielectric properties, such as capacitance control, leakage current formation in dielectric polymer films, and patternability, are described. Strategic approaches to achieve high capacitance based on low‐k dielectric materials, and the development and use of high‐capacitance polymers and hybrid polymer gate dielectrics in the context of emerging transistors on flexible substrates are also discussed.

Understanding, Optimizing, and Utilizing Nonideal Transistors Based on Organic or Organic Hybrid Semiconductors

“…In the case that a single dielectric layer has inferior dielectric properties, using hybrid or multilayer dielectrics has been applied to improve the performance of OFETs as well as sensors and memory . Recently, it demonstrated that using the PMMA/polyacrylic acid (PAA) dielectric revealed extremely suppressed hysteresis and improved mobility compared to those with a pure PAA dielectric ( Figure a) .…”

Sub‐3 V ZnO Electrolyte‐Gated Transistors and Circuits with Screen‐Printed and Photo‐Crosslinked Ion Gel Gate Dielectrics: New Routes to Improved Performance

“…Electrolyte‐gated transistors (EGTs), including electric double layer transistors (EDLTs) and organic electrochemical transistors (OECTs), are being developed by a number of research groups for applications in sensing and printed electronics . Attractive features of EGTs are their very high transconductances and low voltage characteristics, both of which derive from the huge specific capacitance of the electrolyte gate dielectrics that they employ, which varies from ≈10 μF cm −2 in the double layer operating regime to over 100 μF cm −2 in the electrochemical regime …”

Robust High‐Capacitance Polymer Gate Dielectrics for Stable Low‐Voltage Organic Field‐Effect Transistor Sensors

“…An alternative method is to use high‐ k polymer gate dielectrics,17 such as polyelectrolytes or derivatives of poly(vinylidene fluoride‐trifluoroethylene) (PVDF). The hygroscopic nature of polyelectrolytes present a severe disadvantage toward operational stability in ambient conditions 18.…”

“…[14,15] However, in these devices, unreacted hydroxyl groups act as charge trapping sites that are undesirable for stable device operation [16] and large-area processing of robust and uniform ultra-thin films poses a significant challenge for scale-up of these devices. [16] An alternative method is to use high-k polymer gate dielectrics, [17] such as polyelectrolytes or derivatives of poly(vinylidene fluoride-trifluoroethylene) (PVDF). The hygroscopic nature of polyelectrolytes present a severe disadvantage toward operational stability in ambient conditions.…”