Kumar Rajeev, Bocharova Vera, Strelcov Evgheni, Tselev Alexander, Kravchenko Ivan I, Berdzinski Stefan, Strehmel Veronika, Ovchinnikova Olga S, Minutolo Joseph A, Sangoro Joshua R, Agapov Alexander L, Sokolov Alexei P, Kalinin Sergei V, Sumpter Bobby G
Computer Science and Mathematics Division, Oak Ridge National Laboratory, Oak Ridge, TN-37831, USA.
Nanoscale. 2015 Jan 21;7(3):947-55. doi: 10.1039/c4nr05491a.
Polymerized ionic liquids (PolyILs) are promising materials for various solid state electronic applications such as dye-sensitized solar cells, lithium batteries, actuators, field-effect transistors, light emitting electrochemical cells, and electrochromic devices. However, fundamental understanding of interconnection between ionic transport and mechanical properties in PolyILs is far from complete. In this work, local charge transport and structural changes in films of a PolyIL are studied using an integrated experiment-theory based approach. Experimental data for the kinetics of charging and steady state current-voltage relations can be explained by taking into account the dissociation of ions under an applied electric field (known as the Wien effect). Onsager's theory of the Wien effect coupled with the Poisson-Nernst-Planck formalism for the charge transport is found to be in excellent agreement with the experimental results. The agreement between the theory and experiments allows us to predict structural properties of the PolyIL films. We have observed significant softening of the PolyIL films beyond certain threshold voltages and formation of holes under a scanning probe microscopy (SPM) tip, through which an electric field was applied. The observed softening is explained by the theory of depression in glass transition temperature resulting from enhanced dissociation of ions with an increase in applied electric field.
聚合离子液体（PolyILs）是用于各种固态电子应用的有前景的材料，如染料敏化太阳能电池、锂电池、致动器、场效应晶体管、发光电化学电池和电致变色器件。然而，对PolyILs中离子传输与机械性能之间相互联系的基本理解还远未完善。在这项工作中，使用基于实验 - 理论相结合的方法研究了一种PolyIL薄膜中的局部电荷传输和结构变化。通过考虑外加电场下离子的解离（即维恩效应），可以解释充电动力学和稳态电流 - 电压关系的实验数据。发现昂萨格的维恩效应理论与用于电荷传输的泊松 - 能斯特 - 普朗克形式体系与实验结果非常吻合。理论与实验之间的一致性使我们能够预测PolyIL薄膜的结构特性。我们观察到，在超过特定阈值电压时，PolyIL薄膜会显著软化，并且在扫描探针显微镜（SPM）尖端施加电场的情况下会形成孔洞。观察到的软化现象可以用随着外加电场增加离子解离增强导致玻璃化转变温度降低的理论来解释。
