A series
of fully fused n-type mixed conduction lactam polymers
p(g
7
NC
n
N)
, systematically increasing
the alkyl side chain content, are synthesized via an inexpensive,
nontoxic, precious-metal-free aldol polycondensation. Employing these
polymers as channel materials in organic electrochemical transistors
(OECTs) affords state-of-the-art n-type performance with
p(g
7
NC
10
N)
recording an OECT electron mobility of 1.20 ×
10
–2
cm
2
V
–1
s
–1
and a μ
C
* figure of merit
of 1.83 F cm
–1
V
–1
s
–1
. In parallel to high OECT performance, upon solution doping with
(4-(1,3-dimethyl-2,3-dihydro-1
H
-benzoimidazol-2-yl)phenyl)dimethylamine
(N-DMBI), the highest thermoelectric performance is observed for
p(g
7
NC
4
N)
, with a maximum electrical conductivity of
7.67 S cm
–1
and a power factor of 10.4 μW
m
–1
K
–2
. These results are among
the highest reported for n-type polymers. Importantly, while this
series of fused polylactam organic mixed ionic–electronic conductors
(OMIECs) highlights that synthetic molecular design strategies to
bolster OECT performance can be translated to also achieve high organic
thermoelectric (OTE) performance, a nuanced synthetic approach must
be used to optimize performance. Herein, we outline the performance
metrics and provide new insights into the molecular design guidelines
for the next generation of high-performance n-type materials for mixed
conduction applications, presenting for the first time the results
of a single polymer series within both OECT and OTE applications.