Barrier formation at metal/organic interfaces: dipole formation and the Charge Neutrality Level

TL;DR

This paper investigates how energy barriers form at metal/organic interfaces, emphasizing the role of induced interface states and charge transfer, with calculations aligning well with experimental data.

Contribution

It introduces a theoretical analysis using the IDIS model to explain barrier formation, focusing on charge neutrality levels and their impact on interface Fermi levels.

Findings

High induced density of states controls barrier formation

Charge neutrality levels predict interface Fermi levels accurately

Barrier formation driven by charge transfer between metal and organic states

Abstract

The barrier formation for metal/organic semiconductor interfaces is analyzed within the Induced Density of Interface States (IDIS) model. Using weak chemisorption theory, we calculate the induced density of states in the organic energy gap and show that it is high enough to control the barrier formation. We calculate the Charge Neutrality Levels of several organic molecules (PTCDA, PTCBI and CBP) and the interface Fermi level for their contact with a Au(111) surface. We find an excellent agreement with the experimental evidence and conclude that the barrier formation is due to the charge transfer between the metal and the states induced in the organic energy gap.