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Abstract Polymer ferroelectrics are playing an increasingly active role in flexible memory application and wearable electronics. The relaxor ferroelectric dielectric, poly(vinylidene fluoride trifluorethylene (PVDF‐TrFE), although vastly used in organic field‐effect transistors (FETs), has issues with gate leakage current especially when the film thickness is below 500 nm. This work demonstrates a novel method of selective poling the dielectric layer. By using solution‐processed 6,13‐bis(triisopropylsilylethynyl)pentacene (TIPS‐pentacene) as the organic semiconductor, it is shown that textured poling of the PVDF‐TrFE layer dramatically improves FET properties compared to unpoled or uniformly poled ferroelectric films. The texturing is achieved by first vertically poling the PVDF‐TrFE film and then laterally poling the dielectric layer close to the gate electrode. TIPS‐pentacene FETs show on/off ratios of 105and hole mobilities of 1 cm2Vs−1under ambient conditions with operating voltages well below −5 V. The electric field distribution in the dielectric layer is simulated by using finite difference time domain methods.
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Poling induced changes in polarization domain structure of polymer ferroelectrics for application in organic thin film transistors
While electrical poling of organic ferroelectrics has been shown to improve device properties, there are challenges in visualizing accompanying structural changes. We observe poling induced changes in ferroelectric domains by applying differential phase contrast (DPC) imaging in the scanning transmission electron microscope, a method that has been used to observe spatial distributions of electromagnetic fields at the atomic scale. In this work, we obtain DPC images from unpoled and electrically poled polyvinylidene fluoride trifluorethylene films and compare their performance in polymer thin film transistors. The vertically poled films show uniform domains throughout the bulk compared to the unpoled film with a significantly higher magnitude of the overall polarization. Thin film transistors comprising a donor–acceptor copolymer as the active semiconductor layer show improved performance with the vertically poled ferroelectric dielectric film compared with the unpoled ferroelectric dielectric film. A poling field of 80–100 MV/m for the dielectric layer yields the best performing transistors; higher than 100 MV/m is seen to degrade the transistor performance. The results are consistent with a reduction in deleterious charge carrier scattering from ferroelectric domain boundaries or interfacial dipoles arising from electrical poling.
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- Award ID(s):
- 2324839
- PAR ID:
- 10524588
- Publisher / Repository:
- AIP
- Date Published:
- Journal Name:
- Applied Physics Letters
- Volume:
- 124
- Issue:
- 15
- ISSN:
- 0003-6951
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1063/5.0200724
