Cover Picture: Electronic structure of interfaces with conjugated organic materials (Phys. Status Solidi RRL 7/2012)

Abstract

The energy level alignment at interfaces in organic electronic devices is crucial to their function and efficiency. Consequently, device engineers long for rules that allow predicting the energy levels in devices based on parameters of the individual materials, such as work function, ionization energy, and electron affinity. However, the physics and chemistry of interfaces involving conjugated materials can be rather complex, which causes simple models to predict energy levels of two materials in contact often unreliably and can result in errors on the order of several 100 meV. Thorough fundamental investigations of organic/inorganic and organic/organic interfaces over the past two decades have enabled, nonetheless, to derive a few general guidelines that – within limits – enable knowledge-based engineering of interface energy levels. In the Review@RRL by Norbert Koch (pp. 277–293), some considerations regarding the intrinsic electronic properties of conjugated materials are discussed, followed by the most important physico-chemical phenomena occurring upon interface formation, first of organic semiconductors with electrodes and then at organic semiconductor heterojunctions. Where applicable, methods to predictably tune the energy level alignment are introduced as well.