Abstract Polyethyleneimine (PEI) doped single-walled carbon nanotubes (SWCNTs) composites (PEI/SWCNTs) as n-type organic thermoelectric (TE) materials are important candidates for fabricating flexible TE generators. However, the mechanism of unstable TE behavior for PEI/SWCNTs in the air has been not revealed, which hinders the potential application. In this study, we have investigated the influence of CO2, H2O/N2, H2O/CO2, and air on the composition of PEI and TE properties of PEI/SWCNTs. The change of chemical structure shows H2O and CO2 have a series of reactions with the amino of PEI to form ammonium salts, which causes the changes in the types of carriers. The Seebeck coefficient shows that the synergistic effect of H2O and CO2 promotes PEI/SWCNTs changing from n-type to p-type. However, the Seebeck coefficient in dry air shows O2 almost has no influence on the carrier type of PEI/SWCNTs and the n-type PEI/SWCNTs film can be stable for three months in dry air. Noticeably, reversible transformation between n-type and p-type has been realized via regulating the H2O and CO2. The revealed mechanism offers a facile strategy to realize the reversible regulation of TE properties of PEI/SWCNTs and provides a direction for fabricating air-stable n-type PEI/SWCNTs with high TE performance.

中文翻译：

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水和二氧化碳对聚乙烯亚胺/单壁碳纳米管复合材料可逆热电行为的协同作用

摘要 聚乙烯亚胺 (PEI) 掺杂的单壁碳纳米管 (SWCNTs) 复合材料 (PEI/SWCNTs) 作为 n 型有机热电 (TE) 材料是制造柔性热电发生器的重要候选材料。然而，PEI/SWCNTs在空气中不稳定TE行为的机制尚未揭示，这阻碍了其潜在应用。在本研究中，我们研究了 CO2、H2O/N2、H2O/CO2 和空气对 PEI/SWCNT 的 PEI 组成和 TE 性能的影响。化学结构的变化表明H2O和CO2与PEI的氨基发生一系列反应生成铵盐，从而引起载体类型的变化。塞贝克系数表明 H2O 和 CO2 的协同作用促进了 PEI/SWCNTs 从 n 型变为 p 型。然而，干燥空气中的塞贝克系数表明 O2 对 PEI/SWCNTs 的载流子类型几乎没有影响，n 型 PEI/SWCNTs 薄膜在干燥空气中可以稳定三个月。值得注意的是，通过调节 H2O 和 CO2 实现了 n 型和 p 型之间的可逆转变。所揭示的机制为实现PEI/SWCNTs TE性能的可逆调节提供了一种简便的策略，并为制造具有高TE性能的空气稳定n型PEI/SWCNTs提供了方向。