High and Temperature‐Independent Dielectric Constant Dielectrics from PVDF‐Based Terpolymer and Copolymer Blends

Abstract

Relaxor ferroelectric polymers exhibit high k at their structural phase transition around room temperature. They are particularly attractive as gate dielectric in organic field effect transistor (OFET). Nevertheless, their applications are limited due to their low thermal stability. A polymer blend system with a high and thermally stable dielectric constant is demonstrated by mixing terpolymer poly(vinylidene fluoride‐trifluoroethylene‐chlorofluorethylene) P(VDF‐ter‐TrFE‐ter‐CFE) with copolymer poly(vinylidene fluoride‐trifluoroethylene) P(VDF‐co‐TrFE). PVDF‐based blends of various compositions are characterized by dielectric spectroscopy, differential scanning calorimetry (DSC), infrared spectroscopy, small and wide angle X‐ray scattering (SAXS and WAXS), and atomic force microscopy (AFM) in order to investigate the relationship between morphology and crystallization of the blend and their dielectric properties. An optimized blend of P(VDF‐ter‐TrFE‐ter‐CFE) [55/37/8] and P(VDF‐co‐TrFE) [46/54] at a ratio of 70/30 is found to exhibit a quasi‐constant dielectric constant of 40 ± 2 over a wide temperature range (20–80 °C). Furthermore, electrical characteristics of the PVDF‐blend‐based gate dielectric OFET show further thermal stability in comparison to OFET based on high‐k terpolymer P(VDF‐ter‐TrFE‐ter‐CFE) [55/37/8]. An improvement of their drain current stability by up to 60% is demonstrated at 60 °C. These findings enable broader applications of fluoropolymers in organic electronics.

Tailoring fluorinated electroactive polymers toward specific applications

“…Therefore, while in the case of sensors, the resolution increases by increasing the temperature variation of the dielectric constant, high variation would make a flexible display unusable as it would only be able to operate in a very narrow temperature window. To tackle the latter problem, our group has developed an approach where blending P(VDF-co-TrFE) and P(VDF-ter-TrFE-ter-CTFE) leads to almost no variability of dielectric properties over a wide range of temperature [17]. Similar blending approaches have been previously employed for the enhancement of various properties of FEPs, such as ferroelectricity [18], breakdown strength [19], energy density [20] or even electrocaloric cooling potential [21].…”

“…e) output characteristics at different operating temperature of OFETs with terpolymer and f) with the blend system showing improved thermal stability. Reproduced with permission from[17].Copyright (2020)…”

Effect of Composition on Polarization Hysteresis and Energy Storage Ability of P(VDF-TrFE-CFE) Relaxor Terpolymers

“…Small remanent polarization and slim hysteresis make P(VDFx-TrFE1-x-CFEy) terpolymers attractive for energy storage applications [18,19]. A large electrocaloric effect was Therefore, polymers exhibiting high polarizability such as ferroelectric polyvinylidene fluoride P(VDF) and its copolymers with trifluoroethylene (TrFE), hexafluoropropylene (HFP), chlorofluoroethylene (CFE), and chlorotrifluoroethylene (CTFE), as well as blends between them or with other linear dielectric polymers, were studied for energy storage applications [5][6][7][8]. Ideally, all this stored energy should berecoverable, which entails that a remanent contribution to polarization should be small.…”

Low-Power Flexible Organic Field-Effect Transistors with Solution-Processable Polymer-Ceramic Nanoparticle Composite Dielectrics

“…Given the emergence of electronics on skin/organs, rollable displays, printed radio-frequency identification (RFID) tags, electronic papers and wearable sensor, as well as the printability and potential in realizing low-cost and large-area electronic devices, devices with flexible and stretchable organic field-effect transistors (OFETs) have attracted significant attention in the development of next-generation thin-film electronics [1,2].…”