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Observing Ion Motion in Conjugated Polyelectrolytes with Kelvin Probe Force Microscopy
Author(s) -
Collins Samuel D.,
Mikhnenko Oleksandr V.,
Nguyen Thanh Luan,
Rengert Zachary D.,
Bazan Guillermo C.,
Woo Han Young,
Nguyen ThucQuyen
Publication year - 2017
Publication title -
advanced electronic materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.25
H-Index - 56
ISSN - 2199-160X
DOI - 10.1002/aelm.201700005
Subject(s) - materials science , kelvin probe force microscope , ionic bonding , ion , chemical physics , ionic conductivity , analytical chemistry (journal) , nanotechnology , electrode , chemistry , electrolyte , organic chemistry , atomic force microscopy
Conjugated polyelectrolytes (CPEs) are polymer semiconductors whose properties are affected by the presence of covalently fixed and mobile ions. These structural components lead to interfacial dipoles, electrochemical doping, and mixed ionic and electronic conductivity. While the behavior of ionic carriers is important to a number of CPE applications, it remains difficult to quantify ion transport in films due to interference from electronic carriers; relationships between molecular structure and ion conductivity are thus not well understood. This work demonstrates direct observation of ions in six different CPE films using Kelvin probe force microscopy. Surface potential measurements of thin, planar CPE device structures are used to map the distribution of ions through the simple electrostatic relationship between potential and charge density. The transport of mobile ions within the CPE bulk can be studied through the time‐dependent relaxation of bias‐stressed CPE films, through which the decay of ion populations near each electrode is measured and carefully modeled, leading to estimated values of ionic mobility and effective ionic carrier density. The results show that ion transport is most strongly impacted by the number of ion‐bearing side chains per monomer, which facilitate room temperature ion transport via vibrational motion.