High-Performance n-Type Polymeric Mixed Ionic-Electronic Conductors: The Impacts of Halogen Functionalization

Area of Science:

• Materials Science
• Polymer Chemistry
• Organic Electronics

Background:

• Developing high-performance n-type polymer mixed ionic-electronic conductors (PMIECs) is crucial for organic electronic devices like organic electrochemical transistors (OECTs) and organic thermoelectrics (OTEs).
• The performance of these materials is often limited by their charge transport properties and ion uptake capabilities.

Purpose of the Study:

• To synthesize and characterize novel halogen-functionalized PMIECs for improved performance in organic electronics.
• To investigate the impact of halogenation on the electronic and ionic properties of PMIECs.
• To demonstrate the application of these novel materials in high-performance OECTs and OTEs.

Main Methods:

• Synthesis of two halogen-functionalized PMIECs, f-BTI2g-TVTF and f-BTI2g-TVTCl, using fused bithiophene imide dimer (f-BTI2) and halogenated thienylene-vinylene-thienylene (TVT) units.
• Characterization of the polymers' electronic properties, including lowest unoccupied molecular orbital (LUMO) levels and charge transport.
• Evaluation of ion uptake capacity and device performance in OECTs and OTEs.

Main Results:

• The fluorinated f-BTI2g-TVTF exhibited a lower LUMO, enhanced charge transport, and greater ion uptake compared to the control polymer.
• f-BTI2g-TVTF achieved a state-of-the-art charge density (µC*) of 90.2 F cm⁻¹ V⁻¹ s⁻¹ and an electron mobility of 0.41 cm² V⁻¹ s⁻¹ in OECTs.
• An excellent power factor of 64.2 µW m⁻¹ K⁻² was achieved in OTEs.
• An OECT-based inverter amplifier demonstrated a high voltage gain of 148 V V⁻¹.

Conclusions:

• Halogen functionalization, particularly fluorination, is an effective strategy for developing high-performance n-type PMIECs.
• The improved properties of f-BTI2g-TVTF enable state-of-the-art performance in OECTs and OTEs.
• These findings provide valuable insights into the structure-property relationships for designing advanced organic electronic materials.