J-Type Self-Assembled Supramolecular Polymers for High-Performance and Fast-Response n-Type Organic Electrochemical Transistors

To date, high-performance organic electrochemical transistors (OECTs) are almost all based on conjugated polymers. Small molecules can be synthesized with high purity without batch-to-batch variations. However, small molecules require highly crystalline films and good molecular packings to achieve high charge carrier mobilities. Such features make their films unsuitable for ion diffusion or make their molecular packing distorted due to ion diffusion, resulting in poor ion/charge carrier transport properties and slow response speed. Herein, it is proposed to construct small-molecule-based supramolecular polymers to address these issues. A molecule, namely TDPP-RD-G7 is designed, which exhibits J-type self-assembling behaviors and can form supramolecular polymers in solution and conjugated-polymer-like networks in solid state. More importantly, the porous supramolecular polymer networks allow fast ion diffusion and greatly increase the device response speeds. As a result, the TDPP-RD-G7 exhibits record fast response speeds (τ_on/τ_off) of 10.5/0.32 ms with high figure-of-merit (µC*) of 5.88 F cm⁻¹ V⁻¹ s⁻¹ in small-molecule OECTs. This work reveals the possible reasons that hinder the response speeds in small-molecule OECTs and demonstrates a new “supramolecular polymer” approach to high-performance and fast-response small-molecule-based OECTs.