Structural Modifications for Tuning Performance and Operational Modes in n-Type Organic Electrochemical Transistors

Area of Science:

• Materials Science
• Organic Electronics
• Electrochemistry

Background:

• Organic mixed ionic-electronic conductors (OMIECs) are vital for organic electrochemical transistors (OECTs).
• Limited research exists on structure-performance relationships in small-molecule n-type OMIECs.

Purpose of the Study:

• To design and synthesize novel naphthalene diimide (NDI)-based n-type small molecules.
• To investigate the impact of π-conjugation extension and electron-withdrawing groups on OECT performance.
• To establish structure-property correlations for advanced n-type OMIECs.

Main Methods:

• Synthesis of a series of NDI-based small molecules with varied π-conjugation and electron-withdrawing groups.
• Fabrication and characterization of OECTs using the synthesized materials.
• Analysis of electrical properties, including threshold voltage, electron mobility, and transconductance.
• Investigation of self-doping mechanisms and operational stability.

Main Results:

• Achieved a record-low threshold voltage of -0.022 V for OECTs based on 4Br-NDI-3EG.
• Synthesized NDI-DTYA-3EG demonstrated a 2-order improvement in electron mobility (1.04 × 10⁻² cm² V⁻¹ s⁻¹) due to mixed molecular orientation.
• NDI-DTYM-3EG exhibited self-doping capabilities with a low LUMO energy level (-4.51 eV), enabling n-depletion-mode operation.
• NDI-DTYM-3EG-based devices showed high stability, retaining 98% of initial current after 150 minutes.

Conclusions:

• Structural modifications of NDI-based molecules significantly impact OECT performance and operational modes.
• The developed n-type small molecules offer promising characteristics for high-performance OECT applications.
• This work provides valuable insights for designing next-generation n-type OMIEC materials.