Ultrafast direct electron transfer at organic semiconductor and metal interfaces

Area of Science:

• Materials Science
• Physical Chemistry
• Organic Electronics

Background:

• Controlling direct electron transfer is key for developing advanced molecular electronics, light-harvesting materials, and photocatalysis.
• Understanding the relationship between molecular conformation and electron dynamics at interfaces is crucial but remains unclear.

Purpose of the Study:

• To investigate and demonstrate direct electron transfer at buried interfaces between an organic polymer semiconductor and a gold substrate.
• To elucidate the relationship between molecular conformation and electron dynamics in direct electron transfer processes.

Main Methods:

• Utilized dynamical electric field-induced vibrational sum frequency generation (VSFG) spectroscopy to probe electron transfer.
• Performed transient electric field-induced VSFG measurements to analyze time-resolved electron dynamics (<150 fs).
• Employed density functional theory (DFT) calculations to support experimental findings and model molecular configurations.

Main Results:

• Observed dynamical responses (<150 fs) in transient VSFG spectra, confirming direct electron transfer from gold to the organic semiconductor.
• Identified that a subset of surface molecules can adopt specific conformations enabling direct electron transfer, even without deliberate alignment.
• DFT calculations revealed that flat-lying polymer configurations facilitate electron delocalization and transfer across the interface.

Conclusions:

• Direct electron transfer was successfully observed and characterized at complex organic semiconductor-gold interfaces.
• Established a link between specific molecular conformations and ultrafast electron dynamics, providing critical insights for materials design.
• The findings have significant implications for the design and implementation of novel direct electron transfer mechanisms in energy materials and molecular electronics.