Tuning Charge Transport in PVDF-Based Organic Ferroelectric Transistors: Status and Outlook

Abstract

The use of polymer ferroelectric dielectrics in organic field-effect transistors (FETs) for nonvolatile memory application was demonstrated more than 15 years ago. The ferroelectric dielectric polyvinylidene fluoride (PVDF) and its copolymers are most widely used for such applications. In addition to memory applications, polymer ferroelectrics as a dielectric layer in organic FETs yield insights into interfacial transport properties. Advantages of polymer ferroelectric dielectrics are their high dielectric constant compared to other polymer dielectrics and their tunable dielectric constant with temperature. Further, the polarization strength may also be tuned by externally poling the ferroelectric dielectric layer. Thus, PVDF and its copolymers provide a unique testbed not just for investigating polarization induced transport in organic FETs, but also enhancing device performance. This article discusses recent developments of PVDF-based ferroelectric organic FETs and capacitors with a focus on tuning transport properties. It is shown that FET carrier mobilities exhibit a weak temperature dependence as long as the dielectric is in the ferroelectric phase, which is attributed to a polarization fluctuation driven process. The low carrier mobilities in PVDF-based FETs can be enhanced by tuning the poling condition of the dielectric. In particular, by using solution-processed small molecule semiconductors and other donor–acceptor copolymers, it is shown that selective poling of the PVDF-based dielectric layer dramatically improves FET properties. Finally, the prospects of further improvement in organic ferroelectric FETs and their challenges are provided.

High-Performance Multifaceted Piezoelectric Composite Nanogenerators for Weight-Monitoring Sensors

“…The filler concentration-dependent remnant polarization ( P r ) and coercive field ( E c ) values of all of the PS-CFs are shown in Figure b. The nature of the PS-CFs’ P – E loop well matched with the many published reports on PVDF and its composite films. ,, The 0 wt % PS-CF exhibited a P r ≈ 10 nC/cm 2 ( P – E loop area is low), which is increased with the substitution of Se-MRs in the PVDF matrix up to 4 wt % ( P r ≈ 90 nC/cm 2 ). This is due to the improvement in the electrical conduction path between the PVDF molecular chains via the Se-MRs, and the developed pores between the grains may have acted as charge-trapping carriers. − Upon further increasing the Se-MR concentration (i.e., 5 wt %) in the PVDF, the P – E loop area decreased drastically, as shown in Figure a.…”

“…The nature of the PS-CFs' P−E loop well matched with the many published reports on PVDF and its composite films. 21,30,31 The 0 wt % PS-CF exhibited a P r ≈ 10 nC/cm 2 (P−E loop area is low), which is increased with the substitution of Se-MRs in the PVDF matrix up to 4 wt % (P r ≈ 90 nC/cm 2 ). This is due to the improvement in the electrical conduction path between the PVDF molecular chains via the Se-MRs, and the developed pores between the grains may have acted as charge-trapping carriers.…”

Emerging Opportunities for 2D Semiconductor/Ferroelectric Transistor‐Structure Devices

“…[60][61][62][63][64] Besides ferroelectric oxides, organic ferroelectric materials such as poly(vinylidene difluoride-trifluoroethylene) (P(VDF-TrFE)) are an alternative appealing choice for ferroelectric based electronics. [65][66][67][68] Compared to ferroelectric oxides, notwithstanding relatively low spontaneous polarization and high coercive field, PVDF-based ferroelectric polymers hold a great advantage, i.e., much lower crystallization temperature (typically <200 °C) which thus lifts the temperature constraint of deposition ferroelectrics onto 2D layers. Therefore, depending on the desired device design, top-and bottom-gated 2D semiconductor channel with organic ferroelectric polymer gates can both be easily constructed, see Figure 2g.…”

Single-crystal dielectrics for organic field-effect transistors

“…Although the unavoidable rough surface of polymers with polycrystalline texture limits their application in the dielectric layer for OFETs, some semicrystalline polymers show specific properties such as the ferroelectricity of poly(vinylidene fluoride) (PVDF). [66][67][68][69][70] PVDF and its derivatives are widely applied in nonvolatile memory OFET devices as gate dielectrics. The ferroelectricity of PVDF shows a strong dependence on the conformation and orientation of polymer chains, i.e.…”