Structural Effects of Gating Poly(3-hexylthiophene) through an Ionic Liquid
Structural Effects of Gating Poly(3-hexylthiophene) through an Ionic Liquid
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DOI：
10.1002/adfm.201701791
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发表时间：
2017-08-25
影响因子：
19
通讯作者：
Salleo, Alberto
中科院分区：
文献类型：
--
作者：
Guardado, Jesus O.;Salleo, Alberto
离子液体越来越多地被用作有机半导体以产生高电荷密度并实现低电压操作。然而，对活性材料的结构和形态的影响并不完全已知，特别是对于可渗透半导体如共轭聚合物，其中来自离子液体的离子可以进入并电化学掺杂半结晶膜。为了了解离子何时进入，它们去哪里，以及它们如何影响薄膜，原型半导体聚合物聚（3-己基噻吩）的薄膜用1-乙基-3-甲基咪唑鎓双（三氟甲基磺酰基）酰亚胺电化学掺杂，原型离子液体。高分辨率，非原位X-射线衍射测量和完整的极图揭示了随施加电压，循环，和频率的晶格间距，微晶取向，和结晶度的散装和掩埋界面的变化。掺杂离子在足够高的电压和低的频率下穿透膜并进入微晶。在渗透微晶时，离子永久地扩展层状堆叠并收缩π堆叠。循环放大了这些效应，但更高的频率减轻了大块微晶的膨胀，因为离子被阻止进入微晶。这种对离子渗透的结构效应的机械理解将有助于开发电化学掺杂的共轭聚合物的频率和电压阻抗响应的模型，并推进电子应用。
Ionic liquids are increasingly employed as dielectrics to generate high charge densities and enable low-voltage operation with organic semiconductors. However, effects on structure and morphology of the active material are not fully known, particularly for permeable semiconductors such as conjugated polymers, in which ions from the ionic liquid can enter and electrochemically dope the semicrystalline film. To understand when ions enter, where they go, and how they affect the film, thin films of the archetypal semiconducting polymer, poly(3-hexylthiophene), are electrochemically doped with 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, the archetypal ionic liquid. High-resolution, ex situ X-ray diffraction measurements and complete pole figures reveal changes with applied voltage, cycling, and frequency in lattice spacing, crystallite orientation, and crystallinity in the bulk and at the buried interface. Dopant ions penetrate the film and enter the crystallites at sufficiently high voltages and low frequencies. Upon infiltrating crystallites, ions permanently expand lamellar stacking and contract pi-stacking. Cycling amplifies these effects, but higher frequencies mitigate the expansion of bulk crystallites as ions are hindered from entering crystallites. This mechanistic understanding of the structural effects of ion penetration will help develop models of the frequency and voltage impedance response of electrochemically doped conjugated polymers and advance electronic applications.