Observation of Weak Counterion Size Dependence of Thermoelectric Transport in Ion Exchange Doped Conducting Polymers Across a Wide Range of Conductivities
Observation of Weak Counterion Size Dependence of Thermoelectric Transport in Ion Exchange Doped Conducting Polymers Across a Wide Range of Conductivities
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DOI：
10.1002/aenm.202202797
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发表时间：
2023-01-10
影响因子：
27.8
通讯作者：
Sirringhaus, Henning
中科院分区：
文献类型：
--
作者：
Chen, Chen;Jacobs, Ian E.;Sirringhaus, Henning
导电聚合物具有从生物电子学到热电学的广泛应用。控制其复杂电荷传输物理的因素包括这些高掺杂聚合物薄膜中存在的结构无序以及电子电荷载流子和掺杂剂抗衡离子之间的库仑相互作用。先前的研究表明，在低掺杂水平下，载流子被强烈捕获在反离子附近，而在高掺杂水平下，电荷传输不受库仑捕获的限制，这表现在电导率与掺杂剂反离子的尺寸无关。这里使用最近开发的离子交换掺杂方法来研究基于半结晶聚噻吩的模型系统在各种电导率下的离子尺寸依赖性。研究发现，电荷和热电传输不依赖于或仅微弱依赖于离子尺寸的状态延伸至令人惊讶的低电导率。这种令人惊讶的观察结果可以通过异质掺杂来解释，异质掺杂涉及在发生有序结晶域掺杂之前首先将非晶域掺杂到高掺杂水平。这项研究为导电聚合物的热电物理如何随着掺杂水平的变化而演变提供了新的见解。
Conducting polymers are of interest for a broad range of applications from bioelectronics to thermoelectrics. The factors that govern their complex charge transport physics include the structural disorder present in these highly doped polymer films and the Coulombic interactions between the electronic charge carriers and the dopant counterions. Previous studies have shown that at low doping levels carriers are strongly trapped in the vicinity of the counterions, while at high doping levels charge transport is not limited by Coulombic trapping, which manifests itself in the conductivity being independent of the size of the dopant counterion. Here a recently developed ion exchange doping method is used to investigate the ion size dependence of a semicrystalline polythiophene-based model system across a wide range of conductivities. It is found that the regime in which the charge and thermoelectric transport is not or only weakly dependent on ion size, extends to surprisingly low conductivities. This surprising observation is explained by a heterogeneous doping that involves doping of the amorphous domains to high doping levels first before doping of the ordered, crystalline domains occurs. The study provides new insights into how the thermoelectric physics of conducting polymers evolves as a function of doping level.