Interface Structure of MoO3 on Organic Semiconductors

Area of Science:

• Materials Science
• Surface Science
• Organic Electronics

Background:

• Understanding interfaces between metal oxides and organic semiconductors is crucial for organic electronic device performance.
• Molybdenum trioxide (MoO3) is a widely used p-type dopant and electron acceptor in organic electronics.

Purpose of the Study:

• To systematically investigate the interface structure formed by vapor-phase deposition of MoO3 on various organic semiconductors.
• To elucidate the physical, chemical, and electronic evolution of these interfaces during MoO3 deposition.

Main Methods:

• Vapor-phase deposition of MoO3 on eight different organic hole transport materials.
• Characterization using Ultraviolet Photoelectron Spectroscopy (UPS) and X-ray Photoelectron Spectroscopy (XPS).

Main Results:

• Observed diffusion of MoO3 into the organic semiconductor layer, with diffusion increasing as molecular molar mass decreases.
• Identified new carbon and molybdenum core-level states, indicating interfacial electron transfer from the organic semiconductor to MoO3.
• Confirmed energy level alignment at the interface, consistent with the universal energy level alignment rule for molecules on metal oxides, even with inverted deposition order.

Conclusions:

• The study provides fundamental insights into the interfacial behavior of MoO3 on organic semiconductors.
• The findings are critical for designing and optimizing organic electronic devices utilizing MoO3 interfaces.