# 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.

## Key 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.