# Metallic charge transport in conjugated molecular bilayers

## TL;DR

Researchers discovered that molecular bilayers of an organic semiconductor can conduct electricity like metals at very low temperatures, achieving high conductivity and mobility.

## Contribution

The study demonstrates metallic charge transport in organic molecular bilayers at low temperatures, enabled by phenyl bridge coupling and defect control.

## Key findings

- Molecular bilayers showed metallic charge transport down to 8 K with conductivity up to 245 S cm−1.
- Hall mobility exceeded 100 cm2 V−1 s−1 at 20 K due to suppressed molecular vibrations and weakened Coulomb interactions.
- A disorder-driven metal–insulator transition was observed through controlled defect introduction.

## Abstract

Metallic charge transport of field-induced carriers can be observed in single-crystal silicon over a wide temperature range. Such behaviour is rare in undoped organic semiconductors but is beneficial for engineering devices with advanced performance. Here we report metallic charge transport in conjugated molecular bilayers down to 8 K with an electrical conductivity of up to 245 S cm−1 and a Hall mobility larger than 100 cm2 V−1 s−1 at 20 K. We use molecular-crystal bilayers of the organic semiconductor 2-decyl-7-phenyl-[1]benzothieno[3,2-b][1]benzothiophene. We infer that this transport behaviour originates from the phenyl bridge coupling between the two molecular layers, which suppresses molecular vibrations and weakens Coulomb interactions. We develop a controlled method for introducing defects, using which we observe a disorder-driven metal–insulator transition in the molecular crystal.

Molecular bilayer crystals of an organic semiconductor can exhibit metallic charge transport down to 8 K with an electrical conductivity of up to 245 S cm−1, as well as charge carrier mobility values of more than 100 cm2 V−1 s−1 at 20 K.