Air‐Stable Perylene Diimide Trimer Material for N‐Type Organic Electrochemical Transistors

A new method is reported to make air‐stable n‐type organic mixed ionic‐electronic conductor (OMIEC) films for organic electrochemical transistors (OECTs) using a solution‐processable small molecule helical perylene diimide trimer, hPDI[3]‐C11. Alkyl side chains are attached to the conjugated core for processability and film making, which are then cleaved via thermal annealing. After the sidechains are removed, the hPDI[3] film becomes less hydrophobic, more ordered, and has a deeper lowest unoccupied molecular orbital (LUMO). These features provide improved ionic transport, greater electronic mobility, and increased stability in air and in aqueous solution. Subsequently, hPDI[3]‐H is used as the active material in OECTs and a device with a transconductance of 44 mS, volumetric capacitance of ≈250 F cm−3, µC* value of 1 F cm−1 V−1 s−1, and excellent stability (> 5 weeks) is demonstrated. As proof of their practical applications, a hPDI[3]‐H‐based OECTs as a glucose sensor and electrochemical inverter is utilized. The approach of side chain removal after film formation charts a path to a wide range of molecular semiconductors to be used as stable, mixed ionic‐electronic conductors. A method of creating air‐stable small‐molecule n‐type organic mixed ionic‐electronic conductors is reported with helical perylene‐diimide trimer (hPDI[3]) as the model material. Alkyl sidechains are grafted onto the molecular semiconductors to increase its thin‐film solution processability, then removed to create films with better ion transport and stability. High‐transconductance organic electrochemical transistors are made with side‐chainless hPDI[3] as the active material.