Keene Scott T, Laulainen Joonatan E M, Pandya Raj, Moser Maximilian, Schnedermann Christoph, Midgley Paul A, McCulloch Iain, Rao Akshay, Malliaras George G
Electrical Engineering Division, Department of Engineering, University of Cambridge, Cambridge, UK.
Cavendish Laboratory, University of Cambridge, Cambridge, UK.
Nat Mater. 2023 Sep;22(9):1121-1127. doi: 10.1038/s41563-023-01601-5. Epub 2023 Jul 6.
Simultaneous transport and coupling of ionic and electronic charges is fundamental to electrochemical devices used in energy storage and conversion, neuromorphic computing and bioelectronics. While the mixed conductors enabling these technologies are widely used, the dynamic relationship between ionic and electronic transport is generally poorly understood, hindering the rational design of new materials. In semiconducting electrodes, electrochemical doping is assumed to be limited by motion of ions due to their large mass compared to electrons and/or holes. Here, we show that this basic assumption does not hold for conjugated polymer electrodes. Using operando optical microscopy, we reveal that electrochemical doping speeds in a state-of-the-art polythiophene can be limited by poor hole transport at low doping levels, leading to substantially slower switching speeds than expected. We show that the timescale of hole-limited doping can be controlled by the degree of microstructural heterogeneity, enabling the design of conjugated polymers with improved electrochemical performance.
离子电荷与电子电荷的同时传输和耦合是用于能量存储与转换、神经形态计算及生物电子学的电化学装置的基础。虽然使这些技术成为可能的混合导体被广泛使用，但离子传输与电子传输之间的动态关系通常却鲜为人知，这阻碍了新型材料的合理设计。在半导体电极中，由于离子质量相较于电子和/或空穴较大，电化学掺杂被认为受离子运动限制。在此，我们表明这一基本假设不适用于共轭聚合物电极。通过原位光学显微镜，我们发现，在低掺杂水平下，一种先进聚噻吩中的电化学掺杂速度可能受空穴传输不佳的限制，导致开关速度比预期慢得多。我们表明，空穴限制掺杂的时间尺度可通过微观结构不均匀程度来控制，从而能够设计出具有改进电化学性能的共轭聚合物。
