Ultra-Low Threshold Voltage in N-Type Organic Electrochemical Transistors Enabled by Organic Mixed Ionic-Electronic Conductors with Dual Electron-Withdrawing Substitutions

Achieving low threshold voltage (Vth) in organic electrochemical transistors (OECTs) is essential for minimizing power consumption and enhancing sensitivity in bioelectronic devices. However, obtaining OECT materials with ultra-low Vth, close to 0 V for n-type conjugated polymers remains challenging. Here, a conjugated polymer FBDOPV-CNTVT is introduced, which features a rigid backbone structure and high electron deficiency, leading to an exceptionally low lowest unoccupied molecular orbital (LUMO) energy level of -4.67 eV, achieved through dual electron-withdrawing substitutions. With its ultra-low LUMO energy level, FBDOPV-CNTVT exhibits high susceptibility to electrochemical doping, even demonstrating efficient doping near 0 V. Consequently, the OECT device employing FBDOPV-CNTVT as the active material shows an ultra-low Vth of 7.5 mV, setting a new record for the Vth of n-type OECT devices. Furthermore, FBDOPV-CNTVT exhibits a mu C* value of 6.13 F cm-1 V-1 s-1 and retains approximate to 85% of its current after 2000 s cycling. This study highlights the potential of conjugated polymers with dual electron-withdrawing substitutions to achieve ultra-low LUMO energy levels, effectively reducing the Vth of n-type OECT devices and promising advancements in bioelectronics.