  Organic electrochemical transistors (OECTs) have the potential to
revolutionize the field of organic bioelectronics. To date, most of the
reported OECTs include p-type (semi-)conducting polymers as the channel
material, while n-type OECTs are yet at an early stage of development, with the
best performing electron-transporting materials still suffering from low
transconductance, low electron mobility, and slow response time. Here, the high
electrical conductivity of multi-walled carbon nanotubes (MWCNTs) and the large
volumetric capacitance of the ladder-type {\pi}-conjugated redox polymer
poly(benzimidazobenzophenanthroline) (BBL) are leveraged to develop n-type
OECTs with record-high performance. It is demonstrated that the use of MWCNTs
enhances the electron mobility by more than one order of magnitude, yielding
fast transistor transient response (down to 15 ms) and high uC* (electron
mobility x volumetric capacitance) of about 1 F/cmVs. This enables the
development of complementary inverters with a voltage gain of > 16 and a large
worst-case noise margin at a supply voltage of < 0.6 V, while consuming less
than 1 uW of power.
