Backbone Tailoring Enables High-Performance and Stable n-Type Organic Mixed Ionic-Electronic Conductors for Synaptic...

Area of Science:

• Materials Science
• Organic Electronics
• Polymer Chemistry

Background:

• High-performance n-type organic mixed ionic-electronic conductors (OMIECs) are essential for organic electrochemical transistors (OECTs).
• Developing stable n-type OMIECs for applications like complementary circuits and biosensors presents significant challenges.
• Existing OMIECs often lack the required ion-uptake, structural order, and transport capabilities.

Purpose of the Study:

• To design and synthesize novel donor-acceptor polymers for n-type OMIECs.
• To investigate the effect of varying conjugation backbone lengths on polymer properties.
• To optimize OMIECs for high-performance OECTs, artificial synapses, and biosensors.

Main Methods:

• Synthesis of a series of donor-acceptor polymers incorporating bithiophene (BTI) and fused BTI derivatives.
• Fabrication and characterization of conventional and vertical OECTs (vOECTs) using the synthesized polymers.
• Evaluation of OECT performance, including electron mobility, figure-of-merit, and transconductance.
• Demonstration of dual-mode operation (non-volatile and volatile) in vOECTs for synaptic and sensing applications.

Main Results:

• A polymer with a mid-size fused BTI dimer (PBTI2g-DTCN) exhibited enhanced ion-uptake, film order, and transport.
• Achieved electron mobility of 0.84 cm² V^-1 s^-1 and a figure-of-merit (µC*) of 287.8 F cm^-1 V^-1 s^-1 in n-type conventional OECTs.
• vOECTs demonstrated state-of-the-art area-normalized transconductance (g_m,A) of 71.8 µS µm^-2 with excellent operational stability.
• vOECTs showed dual-mode operation, enabling non-volatile artificial synapses for image recognition and volatile biosensing for ECG/EMG signals.

Conclusions:

• Backbone tailoring of donor-acceptor polymers is a highly effective strategy for developing high-performance n-type OMIECs.
• The developed PBTI2g-DTCN polymer significantly advances the capabilities of OECTs for advanced electronic applications.
• The study highlights the potential of tailored OMIECs for next-generation synaptic devices and highly sensitive biosensors.