Microstructure-dependent electrochemical properties of chemical-vapor deposited poly(3,4-ethylenedioxythiophene) (PEDOT) films
Microstructure-dependent electrochemical properties of chemical-vapor deposited poly(3,4-ethylenedioxythiophene) (PEDOT) films
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DOI：
10.1016/j.synthmet.2019.04.022
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发表时间：
2019-07-01
期刊：
影响因子：
4.4
通讯作者：
Ratcliff, Erin L.
中科院分区：
文献类型：
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作者：
Arnold, Sean P.;Harris, Jonathan K.;Ratcliff, Erin L.
由于其固有的机械灵活性以及物理、化学和电子特性的综合可调性，导电聚合物电极在能量转换技术和生物电子学领域具有非凡的前景。溶液处理有利于保持低成本，但由于非共轭侧链和聚离子掺杂剂产生绝缘域，通常会导致物理和电子结构的异质性。这种复杂的情况限制了对基本特性的控制和系统理解，包括对整体设备效率至关重要的电和离子传输以及电子传输速率。氧化化学气相沉积 (oCVD) 提供了一种在低温（< 150 摄氏度）下同时合成和沉积具有可控微结构的导电聚合物薄膜的有前途的途径。在这里，我们使用oCVD技术来合成和沉积不同的聚(3,4-乙撑二氧噻吩)准晶薄膜。利用掠入射广角 X 射线散射，我们展示了 pi-pi 堆积方向相对于表面法线的三种不同方向，以产生具有正面、边缘和各向同性特征的薄膜。这些不同的微观结构对薄膜氧化还原性能的电化学调节有直接影响。我们表明，由能量和功率密度定义的电化学性能对于具有边缘取向的晶体材料来说是最高的，以促进离子传输，同时仍保持合理的电导率。
Conductive polymer electrodes hold exceptional promise in energy conversion technologies and bioelectronics due to the inherent mechanical flexibility and synthetic tunability of physical, chemical, and electronic properties. Solution-processing is favorable to retain low-cost but can often result in heterogeneity of physical and electronic structure due to non-conjugated side chains and polyionic dopants creating insulating domains. Such a complex landscape limits control and systematic understanding of fundamental properties including electrical and ionic transport and rates of electron transfer central to overall device efficiencies. Oxidative chemical vapor deposition (oCVD) offers a promising route to simultaneously synthesize and deposit conductive polymer films at low temperatures (< 150 degrees C) with controllable microstructure. Herein we use the oCVD technique to synthesize and deposit different paracrystalline films of poly(3,4-ethylenedioxythiophene). Using grazing incidence wide-angle x-ray scattering, we demonstrate three different orientations of the pi-pi packing direction, relative to the surface normal, to yield thin films with face-on, edge-on, and isotropic character. These different microstructures have direct impact on the electrochemical conditioning of the redox properties of the films. We show that electrochemical properties, as defined by energy and power density, are highest for crystalline materials with edge-on orientation to facilitate ion transport while still retaining reasonable electrical conductivity.