Ionic Liquid Designed for PEDOT:PSS Conductivity Enhancement,Journal of the American Chemical Society

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Ionic Liquid Designed for PEDOT:PSS Conductivity Enhancement
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2018-04-10 , DOI: 10.1021/jacs.7b10306
Ambroise de Izarra _{1,

2} , Seongjin Park ₁ , Jinhee Lee ₁ , Yves Lansac _{2,

3} , Yun Hee Jang ₁

Affiliation

Poly-3,4-ethylenedioxythiophene:polystyrenesulfonate (PEDOT:PSS) is a water-processable conducting polymer with promise for use in transparent flexible electrodes and thermoelectric devices, but its conductivity is not satisfactory. Its low conductivity is attributed to the formation of hydrophilic/insulating PSS outer layers encapsulating the conducting/hydrophobic p-doped PEDOT cores. Recently a significant conductivity enhancement has been achieved by adding ionic liquid (IL). It is believed that ion exchange between PEDOT:PSS and IL components helps PEDOT to decouple from PSS and to grow into large-scale conducting domains, but the exact mechanism is still under debate. Here we show through free energy calculations using density functional theory on a minimal model that the most efficient IL pairs are the least tightly bound ones with the lowest binding energies, which would lead to the most efficient ion exchange with PEDOT:PSS. This spontaneous ion exchange followed by nanophase segregation between PEDOT and PSS, with formation of a π-stacked PEDOT aggregate decorated by IL anions, is also supported by molecular dynamics performed on larger PEDOT:PSS models in solution. We also show that the most efficient IL anions would sustain the highest amount of charge carriers uniformly distributed along the PEDOT backbone to further enhance the conductivity, providing that they remain in the PEDOT domain after the ion exchange. Hence, our design principle is that the high-performance IL should induce not only an efficient ion exchange with PEDOT:PSS to improve the PEDOT morphology (to increase mobility) but also a uniform high-level p-doping of PEDOT (to enhance intrinsic conductivity). Based on this principle, a promising (electron-withdrawing, but bulky, soft, and hydrophobic) new IL pair is proposed.

中文翻译：

专为 PEDOT 设计的离子液体：PSS 电导率增强

聚 3,4-乙撑二氧噻吩：聚苯乙烯磺酸盐 (PEDOT:PSS) 是一种可水加工的导电聚合物，有望用于透明柔性电极和热电器件，但其导电性并不令人满意。其低导电性归因于形成亲水/绝缘 PSS 外层，封装导电/疏水 p 掺杂 PEDOT 核。最近通过添加离子液体 (IL) 实现了显着的电导率增强。人们认为 PEDOT:PSS 和 IL 组分之间的离子交换有助于 PEDOT 与 PSS 解耦并成长为大规模导电域，但确切机制仍在争论中。在这里，我们通过在最小模型上使用密度泛函理论的自由能计算表明，最有效的 IL 对是结合能最低的最不紧密结合的那些，这将导致与 PEDOT:PSS 进行最有效的离子交换。这种自发的离子交换以及 PEDOT 和 PSS 之间的纳米相分离，形成了由 IL 阴离子装饰的 π 堆积 PEDOT 聚集体，也得到了在溶液中较大 PEDOT:PSS 模型上进行的分子动力学的支持。我们还表明，最有效的 IL 阴离子将维持沿 PEDOT 主链均匀分布的最高数量的电荷载流子，以进一步提高电导率，前提是它们在离子交换后保留在 PEDOT 域中。因此，我们的设计原则是，高性能 IL 不仅应诱导与 PEDOT:PSS 的有效离子交换以改善 PEDOT 形态（以增加迁移率），而且应诱导 PEDOT 的均匀高水平 p 掺杂（以提高本征电导率） . 基于这一原理，提出了一种有前途的（吸电子但体积大、柔软且疏水）的新型 IL 对。

更新日期：2018-04-10

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