Side-Chain Free Semiconducting Polymer for High-Performance n‑Type Organic Electrochemical Transistors

TL;DR

A new method to improve n-type organic electrochemical transistors by modifying polymer films with thermal treatment.

Contribution

A novel post-deposition ester pyrolysis strategy to enhance OECT performance through increased porosity and conductivity.

Findings

The polymer film shows increased porosity, hydrophilicity, and crystallinity after side-chain cleavage.

The μC* figure of merit reaches 158.85 F cm–1 V–1 s–1 with improved transconductance.

Device switching speed and stability are enhanced due to nanoscale porosity.

Abstract

The development of organic electrochemical transistors
(OECTs)
critically depends on the design and characterization of mixed-conducting,
high-performance conjugated polymers (CPs) as channel materials, particularly
for n-type OECTs. In this study, we present a novel strategy to enhance
the OECT performance of a semiconducting polymer film via a postdeposition
ester pyrolysis of thermally cleavable side chains, thus facilitating
ion incorporation and transport within the bulk. Our approach relies
on the synthesis of a high glass-transition, rigid-rod polymer, able
to withstand the pyrolysis temperature without deformation and maintain
the voids formed from the pyrolysis reaction which removes the thermally
cleavable ester side chains. After side-chain cleavage, the resulting
film exhibits increased porosity, hydrophilicity, and crystallinity.
By creating bulk porosity in thin films via this approach, ion diffusion
is enhanced, resulting in a superior μC* figure
of merit up to 158.85 F cm–1 V–1 s–1, and a corresponding increase in normalized
transconductance (31.67 S cm–1). In addition, the
device switching speed and long-term stability are also observed to
increase, further demonstrating the benefit of nanoscale porosity
for mixed conductivity semiconductors.

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