Electrochemical strain microscopy probes morphology-induced variations in ion uptake and performance in organic electrochemical transistors
Electrochemical strain microscopy probes morphology-induced variations in ion uptake and performance in organic electrochemical transistors
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DOI：
10.1038/nmat4918
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发表时间：
2017-07-01
期刊：
影响因子：
41.2
通讯作者：
Ginger, D. S.
中科院分区：
文献类型：
--
作者：
Giridharagopal, R.;Flagg, L. Q.;Ginger, D. S.
有机半导体材料中的离子输运现象是从生物电子学到能量存储等新兴技术的基础。这些系统的性能受到薄膜形态、离子输运和电子输运的相互作用的影响，这是有机半导体所特有的，但人们对其知之甚少。利用原位电化学应变显微镜（ESM），我们证明了我们可以通过测量半导体电化学氧化后离子吸收引起的亚纳米体积膨胀，直接探测聚合物器件中离子传输的局部变化。ESM数据表明，聚（3-己基噻吩）电化学器件表现出电压依赖的非均匀膨胀，与器件操作和电致变色一致。我们的数据表明，聚合物半导体可以同时表现出场效应和电化学操作模式，其操作模式及其分布随着纳米级薄膜形态、离子浓度和电势的局部变化而变化。重要的是，我们通过将应变非均质性与局部刚度图相关联，提供了结构-功能关系的直接测试。这些数据表明，纳米级离子摄取的变化与聚合物填料的局部变化有关，这些变化可能会在不同程度上阻碍离子在同一宏观薄膜内的传输，并为未来的材料优化提供信息。
Ionic transport phenomena in organic semiconductor materials underpin emerging technologies ranging from bioelectronics to energy storage. The performance of these systems is affected by an interplay of film morphology, ionic transport and electronic transport that is unique to organic semiconductors yet poorly understood. Using in situ electrochemical strain microscopy (ESM), we demonstrate that we can directly probe local variations in ion transport in polymer devices by measuring subnanometre volumetric expansion due to ion uptake following electrochemical oxidation of the semiconductor. The ESM data show that poly(3-hexylthiophene) electrochemical devices exhibit voltage-dependent heterogeneous swelling consistent with device operation and electrochromism. Our data show that polymer semiconductors can simultaneously exhibit field-effect and electrochemical operation regimes, with the operation modality and its distribution varying locally as a function of nanoscale film morphology, ion concentration and potential. Importantly, we provide a direct test of structure-function relationships by correlating strain heterogeneity with local stiffness maps. These data indicate that nanoscale variations in ion uptake are associated with local changes in polymer packing that may impede ion transport to different extents within the same macroscopic film and can inform future materials optimization.