Ionic‐Liquid Free and Flexible Transistors Made of 2D Material Inks

Abstract The development of thin‐film transistors (TFTs) using 2D materials is crucial for enabling scalable, low‐cost, and flexible electronics. Currently, 2D TFTs with the highest performance have been achieved by using ionic‐liquid gating (ILG), a technique suited for proof‐of‐concept studies. However, ILG suffers from slow switching speeds, temperature sensitivity, poor long‐term stability, and integration challenges, making it unsuitable for practical use. Moreover, typical fabrication methods for 2D TFTs involve harsh conditions such as strong acids or high temperatures (>300 °C), limiting integration with flexible substrates. This work provides the first demonstration of an ILG‐free, all‐2D‐material TFT fabricated onto a flexible substrate. Water‐based graphene and hexagonal boron nitride (h‐BN) inks are printed to deposit the electrodes and dielectric layers, respectively. The MoS ₂ channel is produced via supramolecular interfacial self‐assembly, yielding uniform, monolayer‐rich films transferable to rigid and flexible substrates. The resulting TFTs operate below 3 V, exhibit negligible leakage current, and achieve field‐effect mobilities up to 0.46 cm ² V ⁻¹ s ⁻¹ (rising to 2.47 cm ² V ⁻¹ s ⁻¹ with silver electrodes) measured under ambient conditions, while maintaining excellent mechanical flexibility. This work establishes a low‐cost and scalable solution‐processable platform for flexible electronics based on 2D materials that match requirements for practical applications.