Electronic Properties of Metal-Organic Interfaces with Application to Electroluminescent Devices

Abstract
The electronic structure of metal-organic molecular semiconductor interfaces is investigated via photoemission spectroscopy. We measured the energy offsets between the organic molecular levels and the metal Fermi level, which correspond to the charge injection barriers. Chemical reaction and interdiffusion dominate the behavior of metal-on-top contacts. Organic-on-top interfaces are found to be more abrupt. The present data demonstrate that the rule of vacuum level alignment breaks down and that the effect of electronic gap states cannot be neglected at these interfaces.