Switching p-type to high-performance n-type organic electrochemical transistors via doped state engineering

High-performance n-type organic electrochemical transistors (OECTs) are essential for logic circuits and sensors. However, the performances of n-type OECTs lag far behind that of p-type ones. Conventional wisdom posits that the LUMO energy level dictates the n-type performance. Herein, we show that engineering the doped state is more critical for n-type OECT polymers. By balancing more charges to the donor moiety, we could effectively switch a p-type polymer to high-performance n-type material. Based on this concept, the polymer, P(gTDPP2FT), exhibits a record high n-type OECT performance with μC* of 54.8 F cm⁻¹ V⁻¹ s⁻¹, mobility of 0.35 cm² V⁻¹ s⁻¹, and response speed of τon/τoff = 1.75/0.15 ms. Calculations and comparison studies show that the conversion is primarily due to the more uniform charges, stabilized negative polaron, enhanced conformation, and backbone planarity at negatively charged states. Our work highlights the critical role of understanding and engineering polymers' doped states.

高性能n型有机电化学晶体管（organic electrochemical transistors, OECTs）是逻辑电路与传感器不可或缺的核心器件。然而当前n型OECT的性能仍远落后于p型器件。传统观点普遍认为，最低未占据分子轨道（lowest unoccupied molecular orbital, LUMO）能级是决定n型OECT性能的核心因素。本研究表明，调控聚合物的掺杂态对n型OECT用聚合物而言更为关键。通过向给体单元平衡分配更多电荷，可将一款p型聚合物有效转化为高性能n型活性材料。基于该设计思路，聚合物P(gTDPP2FT)展现出创纪录的高性能n型OECT性能：其μC*可达54.8 F cm⁻¹ V⁻¹ s⁻¹，载流子迁移率为0.35 cm² V⁻¹ s⁻¹，响应速度τon/τoff为1.75/0.15 ms。计算与对比研究证实，该性能提升主要源于负电荷态下电荷分布更均匀、负极化子稳定性提升、构象优化以及主链平面性增强。本研究凸显了理解并精准调控聚合物掺杂态的关键作用。