Balancing ionic and electronic conduction for high‐performance organic electrochemical transistors

by Achilleas Savva, Rawad Hallani, Camila Cendra, Jokubas Surgailis, Tania C. Hidalgo, Shofarul Wustoni, Rajendar Sheelamanthula, Xingxing Chen, Mindaugas Kirkus, Alexander Giovannitti, Alberto Salleo, Iain McCulloch, Sahika Inal
Year: 2020 DOI: 10.1002/adfm.201907657

Bibliography

Balancing ionic and electronic conduction for high‐performance organic electrochemical transistors
Achilleas Savva, Rawad Hallani, Camila Cendra, Jokubas Surgailis, Tania C. Hidalgo, Shofarul Wustoni, Rajendar Sheelamanthula, Xingxing Chen, Mindaugas Kirkus, Alexander Giovannitti, Alberto Salleo, Iain McCulloch, Sahika Inal
Advanced Functional Materials, Volume 30, Issue 11, 1 March 2020

Abstract

Conjugated polymers that support mixed (electronic and ionic) conduction are in demand for applications spanning from bioelectronics to energy harvesting and storage. To design polymer mixed conductors for high‐performance electrochemical devices, relationships between the chemical structure, charge transport, and morphology must be established. A polymer series bearing the same p‐type conjugated backbone with increasing percentage of hydrophilic, ethylene glycol side chains is synthesized, and their performance in aqueous electrolyte gated organic electrochemical transistors (OECTs) is studied. By using device physics principles and electrochemical analyses, a direct relationship is found between the OECT performance and the balanced mixed conduction. While hydrophilic side chains are required to facilitate ion transport—thus enabling OECT operation—swelling of the polymer is not de facto beneficial for balancing mixed conduction. It is shown that heterogeneous water uptake disrupts the electronic conductivity of the film, leading to OECTs with lower transconductance and slower response times. The combination of in situ electrochemical and structural techniques shown here contributes to the establishment of the structure–property relations necessary to improve the performance of polymer mixed conductors and subsequently of OECTs.

Keywords

Atomic force microscopy Conjugated polymers Mixed ionic–electronic conduction Organic bioelectronics Organic electrochemical transistors