Laudari Amrit, Barron John, Pickett Alec, Guha Suchismita
Department of Physics and Astronomy, University of Missouri, Columbia, Missouri 65211, United States.
ACS Appl Mater Interfaces. 2020 Jun 17;12(24):26757-26775. doi: 10.1021/acsami.0c05731. Epub 2020 Jun 4.
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.
15年多前就已证明了聚合物铁电介质在用于非易失性存储器应用的有机场效应晶体管（FET）中的应用。铁电介质聚偏二氟乙烯（PVDF）及其共聚物在这类应用中使用最为广泛。除了存储器应用外，聚合物铁电体作为有机FET中的介电层还能深入了解界面传输特性。聚合物铁电介质的优点是与其他聚合物介质相比具有较高的介电常数，并且其介电常数随温度可调。此外，还可以通过对铁电介质层进行外部极化来调节极化强度。因此，PVDF及其共聚物不仅为研究有机FET中极化诱导的传输提供了一个独特的试验平台，还能提高器件性能。本文讨论了基于PVDF的铁电有机FET和电容器的最新进展，重点是调节传输特性。结果表明，只要电介质处于铁电相，FET载流子迁移率就表现出较弱的温度依赖性，这归因于极化涨落驱动的过程。基于PVDF的FET中较低的载流子迁移率可以通过调节电介质的极化条件来提高。特别是，通过使用溶液处理的小分子半导体和其他供体-受体共聚物，结果表明对基于PVDF的介电层进行选择性极化可显著改善FET性能。最后，给出了有机铁电FET进一步改进的前景及其面临的挑战。
