Smith Brittany N, Meikle Hope, Doherty James L, Lu Shiheng, Tutoni Gianna, Becker Matthew L, Therien Michael J, Franklin Aaron D
Department of Electrical and Computer Engineering, Duke University, Durham, NC 27708, USA.
Department of Chemistry, Duke University, Durham, NC 27708, USA.
Nanoscale. 2022 Nov 24;14(45):16845-16856. doi: 10.1039/d2nr04206a.
Printed carbon nanotube thin-film transistors (CNT-TFTs) are candidates for flexible electronics with printability on a wide range of substrates. Among the layers comprising a CNT-TFT, the gate dielectric has proven most difficult to additively print owing to challenges in film uniformity, thickness, and post-processing requirements. Printed ionic dielectrics show promise for addressing these issues and yielding devices that operate at low voltages thanks to their high-capacitance electric double layers. However, the printing of ionic dielectrics in their various compositions is not well understood, nor is the impact of certain stresses on these materials. In this work, we studied three compositionally distinct ionic dielectrics in fully printed CNT-TFTs: the polar-fluorinated polymer elastomer PVDF-HFP; an ion gel consisting of triblock polymer PS-PMMA-PS and ionic liquid EMIM-TFSI; and crystalline nanocellulose (CNC) with a salt concentration of 0.05%. Although ion gel has been thoroughly studied, e-PVDF-HFP and CNC printing are relatively new and this study provides insights into their ink formulation, print processing, and performance as gate dielectrics. Using a consistent aerosol jet printing approach, each ionic dielectric was printed into similar CNT-TFTs, allowing for direct comparison through extensive characterization, including mechanical and electrical stress tests. The ionic dielectrics were found to have distinct operational dependencies based on their compositional and ionic attributes. Overall, the results reveal a number of trade-offs that must be managed when selecting a printable ionic dielectric, with CNC showing the strongest performance for low-voltage operation but the ion gel and elastomer exhibiting better stability under bias and mechanical stresses.
印刷碳纳米管薄膜晶体管（CNT-TFT）是用于柔性电子器件的候选材料，具有在多种基板上进行印刷的能力。在构成CNT-TFT的各层中，由于在薄膜均匀性、厚度和后处理要求方面存在挑战，栅极电介质已被证明最难通过添加方式进行印刷。印刷离子电介质有望解决这些问题，并由于其高电容双电层而产生能够在低电压下工作的器件。然而，对于各种组成的离子电介质的印刷了解并不充分，某些应力对这些材料的影响也不清楚。在这项工作中，我们研究了全印刷CNT-TFT中三种成分不同的离子电介质：极性氟化聚合物弹性体PVDF-HFP；由三嵌段聚合物PS-PMMA-PS和离子液体EMIM-TFSI组成的离子凝胶；以及盐浓度为0.05%的结晶纳米纤维素（CNC）。尽管离子凝胶已被深入研究，但e-PVDF-HFP和CNC印刷相对较新，本研究提供了有关它们作为栅极电介质的油墨配方、印刷工艺和性能的见解。使用一致的气溶胶喷射印刷方法，将每种离子电介质印刷到类似的CNT-TFT中，通过包括机械和电应力测试在内的广泛表征进行直接比较。发现离子电介质基于其组成和离子属性具有不同的操作依赖性。总体而言，结果揭示了在选择可印刷离子电介质时必须权衡的一些因素，CNC在低电压操作方面表现出最强的性能，但离子凝胶和弹性体在偏置和机械应力下表现出更好的稳定性。
