Effects of film thickness on electrochemical properties of nanoscale polyethylenedioxythiophene (PEDOT) thin films grown by oxidative molecular layer deposition (oMLD)
Effects of film thickness on electrochemical properties of nanoscale polyethylenedioxythiophene (PEDOT) thin films grown by oxidative molecular layer deposition (oMLD)
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DOI：
10.1039/d3nr00708a
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发表时间：
2023-03-02
期刊：
影响因子：
6.7
通讯作者：
Young，Matthias J.
中科院分区：
文献类型：
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作者：
Brathwaite，Katrina G.;Wyatt，Quinton K.;Young，Matthias J.
聚（3,4-乙烯二氧噻吩）（PEDOT）具有很高的理论电荷存储容量，使其在包括储能和海水淡化在内的电化学应用中备受关注。纳米级的PEDOT薄膜在这些应用中特别有吸引力，可以实现更快的充电。最近的研究表明，PEDOT的纳米级薄膜可以通过氧化分子层沉积（oMLD）的连续气相暴露形成，与其他沉积技术相比，它在高纵横比衬底上具有一致性和均匀性的优势。但迄今为止，这些oMLD PEDOT薄膜的电化学性能还没有得到很好的表征。在这项工作中，我们研究了5-100 nm厚的PEDOT薄膜通过20-175个oMLD沉积循环形成的电化学性能。我们发现oMLD PEDOT薄膜的厚度会影响有序畴的取向，从而导致电荷存储容量的实质性变化。有趣的是，我们观察到oMLD PEDOT薄膜厚度的最小电荷存储容量为~ 30 nm（150°C下60个oMLD循环），与使用掠入射广角x射线散射（GIWAXS）测量的面向PEDOT畴的最高程度相一致。更薄和更厚的oMLD PEDOT薄膜表现出更高的倾斜（非角度）取向，相应的电荷容量增加高达120 mA h g−1。电化学测量表明，具有混合畴取向的薄膜中较高的电荷容量是由于离子从液体电解质容易传输到PEDOT层。更大的电解质暴露于PEDOT域边缘，以促进这些混合域膜中更快的离子传输。这些见解将为未来设计用于电化学储能和水处理的PEDOT涂层高纵横比结构提供信息。
Poly(3,4-ethylene dioxythiophene) (PEDOT) has a high theoretical charge storage capacity, making it of interest for electrochemical applications including energy storage and water desalination. Nanoscale thin films of PEDOT are particularly attractive for these applications to enable faster charging. Recent work has demonstrated that nanoscale thin films of PEDOT can be formed using sequential gas-phase exposures via oxidative molecular layer deposition, or oMLD, which provides advantages in conformality and uniformity on high aspect ratio substrates over other deposition techniques. But to date, the electrochemical properties of these oMLD PEDOT thin films have not been well-characterized. In this work, we examine the electrochemical properties of 5–100 nm thick PEDOT films formed using 20–175 oMLD deposition cycles. We find that film thickness of oMLD PEDOT films affects the orientation of ordered domains leading to a substantial change in charge storage capacity. Interestingly, we observe a minimum in charge storage capacity for an oMLD PEDOT film thickness of ∼30 nm (60 oMLD cycles at 150 °C), coinciding with the highest degree of face-on oriented PEDOT domains as measured using grazing incidence wide angle X-ray scattering (GIWAXS). Thinner and thicker oMLD PEDOT films exhibit higher fractions of oblique (off-angle) orientations and corresponding increases in charge capacity of up to 120 mA h g−1. Electrochemical measurements suggest that higher charge capacity in films with mixed domain orientation arise from the facile transport of ions from the liquid electrolyte into the PEDOT layer. Greater exposure of the electrolyte to PEDOT domain edges is posited to facilitate faster ion transport in these mixed domain films. These insights will inform future design of PEDOT coated high-aspect ratio structures for electrochemical energy storage and water treatment.