Doping-Induced Electron Transfer at Organic/Oxide Interfaces: Direct Evidence from Infrared Spectroscopy.

Area of Science:

• Surface Science
• Materials Chemistry
• Organic Electronics

Background:

• Charge transfer at organic/inorganic interfaces is key to molecular adlayer properties.
• Evidence for charge transfer from high ionization energy oxides to molecular acceptors is scarce.
• Understanding these interfaces is critical for developing advanced electronic materials.

Purpose of the Study:

• To provide direct experimental evidence of electron transfer from ZnO to a molecular acceptor.
• To elucidate the mechanisms governing interfacial charge transfer and molecular vibrational shifts.
• To investigate the role of n-doping in ZnO for interfacial charge dynamics.

Main Methods:

• Infrared reflection-absorption spectroscopy (IRRAS) was employed to study molecular adlayers.
• Density functional theory (DFT) calculations were used for thorough theoretical analysis.
• Combined experimental and theoretical approaches were utilized to interpret spectral data.

Main Results:

• Direct evidence of electron transfer from ZnO to hexafluoro-tetracyano-naphthoquinodimethane (F6-TCNNQ) was demonstrated.
• Pronounced vibrational red shifts in F6-TCNNQ were observed and explained by two mechanisms.
• Calculations revealed electron transfer into molecular orbitals and bonding between Zn and cyano groups.

Conclusions:

• This study presents the first evidence of interfacial electron transfer from high ionization energy inorganic semiconductors to molecular acceptors.
• The findings highlight the significant role of n-doping in ZnO for facilitating charge transfer.
• The combined experimental and theoretical approach offers a robust method for studying such interfaces.