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.

中文翻译：

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电化学应变显微镜可探测有机电化学晶体管中由形态引起的离子吸收和性能变化

有机半导体材料中的离子传输现象支持了从生物电子到能量存储等新兴技术。这些系统的性能受薄膜形态，离子传输和电子传输之间相互作用的影响，这是有机半导体独有的，但人们对此知之甚少。原位使用电化学应变显微镜（ESM），我们证明了通过测量半导体电化学氧化后由于离子吸收而导致的亚纳米级体积膨胀，我们可以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）电化学装置表现出与装置操作和电致变色一致的电压依赖性异质膨胀。我们的数据表明，聚合物半导体可以同时显示场效应和电化学操作方式，其操作方式及其分布随纳米级薄膜形态，离子浓度和电势的变化而局部变化。重要的是，我们通过将应变异质性与局部刚度图相关联来直接测试结构与功能的关系。