Columnar Mesomorphism in a Methylthio-Decorated Triindole for Enhanced Charge Transport

Area of Science:

• Materials Science
• Organic Electronics
• Supramolecular Chemistry

Background:

• Discotic liquid crystals are promising for organic electronics due to their self-assembly properties.
• Controlling molecular packing and supramolecular organization is crucial for optimizing charge transport.
• Triindole-based molecules offer a unique core structure for designing functional liquid crystals.

Purpose of the Study:

• To synthesize and characterize a novel semiconducting triindole-based discotic liquid crystal (TRISMe).
• To investigate the influence of methylthio groups on the supramolecular organization and mesophase behavior of TRISMe.
• To evaluate the charge transport properties of TRISMe based on different processing methods (solution vs. melt).

Main Methods:

• Synthesis and characterization of the TRISMe compound.
• Differential scanning calorimetry (DSC) and polarized optical microscopy (POM) for mesophase analysis.
• Single crystal X-ray diffraction for structural elucidation.
• Space-charge-limited current (SCLC) measurements for hole mobility in diode-type devices.
• Fabrication and testing of organic field-effect transistors (OFETs) for solution-processed devices.

Main Results:

• TRISMe forms a stable columnar hexagonal mesophase upon heating, facilitated by peripheral methylthio groups that prevent tight packing.
• Single crystal analysis confirms the propensity for columnar architecture and the stabilizing role of methylthio groups.
• Melt-processed TRISMe in diode-type devices exhibits high hole mobility (3 × 10⁻¹ cm²/V·s).
• Solution-processed crystalline TRISMe in OFETs shows lower hole mobility (3 × 10⁻⁴ cm²/V·s).

Conclusions:

• Methylthio functionalization effectively promotes stable columnar mesophases in triindole-based liquid crystals.
• Melt processing of TRISMe leads to superior charge transport compared to solution processing, attributed to beneficial supramolecular assembly.
• TRISMe is a promising material for developing easily processable organic electronic devices with high performance.