Ultrafast Charge Transfer Pathways Through A Prototype Amino-Carboxylic Molecular Junction

Area of Science:

• Organic electronics
• Materials science
• Surface science

Background:

• Understanding charge transport in organic heterojunctions is crucial for developing advanced electronic devices.
• Hydrogen bonding offers a potential mechanism for controlling molecular interactions and electronic properties.

Purpose of the Study:

• To investigate the impact of amino-carboxylic (A-C) hydrogen bonding on charge transport in a vertically stacked organic heterojunction.
• To explore the site-selective charge transport pathways facilitated by A-C hydrogen bonds.

Main Methods:

• Utilized X-ray resonant photoemission spectroscopy to probe electronic structure.
• Employed the core-hole clock method to determine charge transport dynamics.
• Fabricated and analyzed molecular bilayers of benzoic acid (BA) and cysteamine (CA) on a gold substrate.

Main Results:

• Demonstrated that A-C hydrogen bonding in BA/CA bilayers creates an ultrafast, site-selective charge transport pathway.
• Observed that cysteamine hinders electron delocalization from the benzoic acid phenyl group.
• Revealed the opening of a fast charge delocalization route through benzoic acid orbitals near the A-C bond.

Conclusions:

• A-C hydrogen bonding can be strategically used to spatially and orbitally control charge transport in heteromolecular junctions.
• This finding provides a pathway for designing organic electronic materials with tailored charge transport characteristics.