Surfactant-Wrapped n-Type Organic Thermoelectric Carbon Nanotubes for Long-Term Air Stability and Power Characteristics
Surfactant-Wrapped n-Type Organic Thermoelectric Carbon Nanotubes for Long-Term Air Stability and Power Characteristics
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DOI：
10.1021/acsaelm.1c01256
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发表时间：
2022-03-22
影响因子：
4.7
通讯作者：
Toshima, Naoki
中科院分区：
文献类型：
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作者：
Hata, Shinichi;Maeshiro, Kanto;Toshima, Naoki
n型碳纳米管（CNT）的低空气稳定性和不利的功率特性限制了柔性电子和有机晶体管的发展。因此，确定最佳的 n 型掺杂剂仍然至关重要。我们提出在纳米管上吸附表面活性剂层的高表面覆盖率，以保持连续的载流子稳定性并保持n型材料的有机热电性能。尾长为 8 或 12 个碳原子（8-3-8 和 12-3-12）的双子表面活性剂的水溶液被用作纳米管的分散剂。双子表面活性剂比单链表面活性剂更大程度地促进纳米管的分散，最终提高薄膜的热电性能。优化后的 12-3-12/CNT 的面内无量纲品质因数为 6.04 x 10(-3)，与油溶性掺杂剂相当。此外，由于负塞贝克系数的降低导致功率因数显着下降，因此之前没有在传统系统中研究超过100天的n型热电特性。因此，我们评估了使用8-3-8和12-3-12制造的碳纳米管的空气稳定性，观察到双子表面活性剂比单链表面活性剂更大程度地延长了n型载流子的寿命并增强了热电性能。在空气中放置 120 天后，12-3-12/CNT 保留了大约 83% 的初始功率特性，这归因于纳米管上吸附的双子表面活性剂的高表面积。裸露纳米管的低比表面积减少了氧的可及面积，抑制了大气中氧气引起的空穴掺杂，提高了n型碳纳米管的稳定性和功率特性。因此，未来设计表面活性剂来控制阳离子分子吸附的形式对于实现 n 型材料的持续空气稳定性和有利的输出特性至关重要。
The low air stability and unfavorable power properties of n-type carbon nanotubes (CNTs) limit the development of flexible electronics and organic transistors. Hence, determining an optimal n-dopant remains crucial. We propose the high surface coverage of adsorbed surfactant layers on nanotubes to maintain a continuous carrier stability and preserve the organic thermoelectric properties of n-type materials. Aqueous solutions of gemini surfactants with a tail length of 8 or 12 C atoms (8-3-8 and 12-3-12) were used as dispersants for the nanotubes. The gemini surfactants facilitated the enhanced dispersion of nanotubes to a greater degree than single-chain surfactants, ultimately improving the thermoelectric performance of films. An in-plane dimensionless figure-of-merit value of 6.04 x 10(-3) was recorded for the optimized 12-3-12/CNTs, which was comparable to that of oil-soluble dopants. In addition, the n-type thermoelectric characteristics had not been previously investigated beyond 100 d in conventional systems because of a significant drop in the power factor, which was caused by a decrease in the negative Seebeck coefficient. We therefore evaluated the air stabilities of CNTs fabricated using 8-3-8 and 12-3-12, observing that gemini surfactants extended the lifetimes and enhanced the thermoelectric performances of n-type carriers to a greater extent than single-chain surfactants. Approximately 83% of the initial power characteristics were retained for 12-3-12/CNTs after 120 d under air, which was attributed to the high surface area of the adsorbed gemini surfactant on the nanotubes. The low specific surface areas of the bare nanotubes reduced the oxygen-accessible area, suppressing hole doping caused by atmospheric oxygen and improving the stabilities and power characteristics of n-type CNTs. The future design of surfactants to control the form of cationic molecular adsorption is therefore essential to achieve sustained air stabilities and favorable output properties for n-type materials.