Metallic charge transport in conjugated molecular bilayers

Area of Science:

• Materials Science
• Condensed Matter Physics
• Organic Electronics

Background:

• Metallic charge transport is common in inorganic semiconductors like silicon but rare in undoped organic semiconductors.
• Achieving high performance in organic electronic devices requires understanding and controlling charge transport mechanisms.

Purpose of the Study:

• To investigate metallic charge transport in conjugated molecular bilayers.
• To explore the underlying mechanisms and potential for device applications.

Main Methods:

• Fabrication of molecular-crystal bilayers using 2-decyl-7-phenyl-[1]benzothieno[3,2-b][1]benzothiophene.
• Electrical conductivity and Hall mobility measurements down to 8 K.
• Controlled introduction of defects to study disorder effects.

Main Results:

• Observed metallic charge transport in conjugated molecular bilayers down to 8 K.
• Achieved electrical conductivity up to 245 S cm^-1 and Hall mobility > 100 cm² V^-1 s^-1 at 20 K.
• Demonstrated a disorder-driven metal-insulator transition upon defect introduction.

Conclusions:

• The phenyl bridge coupling in molecular bilayers suppresses vibrations and Coulomb interactions, enabling metallic transport.
• Organic molecular crystals can exhibit robust metallic behavior, opening avenues for advanced organic electronics.
• Defect engineering provides a route to tune the electronic properties of organic semiconductors.