Hole-limited electrochemical doping in conjugated polymers

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Science

Background:

• Simultaneous ionic and electronic charge transport is crucial for electrochemical devices.
• Understanding the interplay between ionic and electronic transport in mixed conductors is limited.
• Current assumptions suggest ion mobility limits electrochemical doping in semiconducting electrodes.

Purpose of the Study:

• To investigate the factors limiting electrochemical doping speeds in conjugated polymer electrodes.
• To challenge the assumption that ion motion is the sole limiting factor in doping.
• To identify strategies for enhancing the electrochemical performance of conjugated polymers.

Main Methods:

• Operando optical microscopy was employed to study doping dynamics.
• Investigation focused on a state-of-the-art polythiophene electrode.
• Analysis correlated doping speeds with microstructural heterogeneity.

Main Results:

• Electrochemical doping in conjugated polymers can be limited by hole transport, especially at low doping levels.
• This hole-limited transport leads to slower switching speeds than predicted by ion-mobility-limited models.
• The degree of microstructural heterogeneity was found to influence the timescale of hole-limited doping.

Conclusions:

• The assumption that ion motion limits doping is not universally applicable to conjugated polymers.
• Hole transport dynamics play a significant role in the electrochemical performance of these materials.
• Tailoring microstructural heterogeneity offers a pathway to design conjugated polymers with improved doping speeds and device performance.