In Situ Studies of the Swelling by an Electrolyte in Electrochemical Doping of Ethylene Glycol-Substituted Polythiophene
In Situ Studies of the Swelling by an Electrolyte in Electrochemical Doping of Ethylene Glycol-Substituted Polythiophene
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DOI：
10.1021/acsami.2c06169
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发表时间：
2022-06-13
影响因子：
9.5
通讯作者：
Richter, Lee J.
中科院分区：
文献类型：
--
作者：
Flagg, Lucas Q.;Asselta, Lauren E.;Richter, Lee J.
有机混合离子电子导体（OMIECs）具有实现各种新技术的潜力，从生物传感器到灵活的储能设备和神经形态计算平台。然而，这些材料在其操作状态下的研究是极其困难的，抑制了合理的材料设计，所述操作状态涉及被动和电势驱动的溶剂、阳离子和阴离子进入。在这份报告中，我们提出了一种新的方法，通过掠入射X-射线散射的电化学开关的原型OMIEC的基础上的低聚乙二醇（oEG）取代的半结晶regioregular聚噻吩的原位研究。通过研究干燥和与电解质接触的晶格，同时保持电位控制，我们可以直接观察结晶域的演变及其与电化学门控晶体管中的膜性能的关系。尽管OEG侧链使本体电解质吸收，我们发现，结晶区域是相对疏水的，表现出很少（小于一个水每噻吩）的未掺杂的聚合物的溶胀，这表明无定形区域占主导地位的被动溶胀行为。随着施加的电位，我们观察到，在晶体中的π-π分离合同，而片层间距增加，在一个平衡的方式，导致在一个可以忽略不计的变化，在晶体体积。晶体结构中的电位诱导的变化不清楚地与作为有机电化学晶体管的膜的电性能相关，这表明晶体管性能受到膜的非晶区域的强烈影响。
Organic mixed ionic electronic conductors (OMIECs) have the potential to enable diverse new technologies, ranging from biosensors to flexible energy storage devices and neuromorphic computing platforms. However, a study of these materials in their operating state, which convolves both passive and potential-driven solvent, cation, and anion ingress, is extremely difficult, inhibiting rational material design. In this report, we present a novel approach to the in situ studies of the electrochemical switching of a prototypical OMIEC based on oligoethylene glycol (oEG) substitution of semicrystalline regioregular polythiophene via grazing-incidence X-ray scattering. By studying the crystal lattice both dry and in contact with the electrolyte while maintaining potential control, we can directly observe the evolution of the crystalline domains and their relationship to film performance in an electrochemically gated transistor. Despite the oEG side-chain enabling bulk electrolyte uptake, we find that the crystalline regions are relatively hydrophobic, exhibiting little (less than one water per thiophene) swelling of the undoped polymer, suggesting that the amorphous regions dominate the reported passive swelling behavior. With applied potential, we observe that the pi-pi separation in the crystals contracts while the lamella spacing increases in a balanced fashion, resulting in a negligible change in the crystal volume. The potential-induced changes in the crystal structure do not clearly correlate to the electrical performance of the film as an organic electrochemical transistor, suggesting that the transistor performance is strongly influenced by the amorphous regions of the film.