Interfaces in organic semiconductor devices

The importance of interfacial properties in organic light emitting devices is well recognized. The mismatch between a strong metallic lattice and a weak Van-der-Waals organic solid at the metal/organic interface can result in an interfacial structure which is uniquely different from those commonly found in metal/inorganic semiconductors. We will discuss the relations between energy level alignment, interface charge transfer, dipole layer formation, and the ultimate consequences of these effects on the device characteristics and performance. The discussion will mainly be based on measurements using surface/interface analytical techniques including X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, and inverse photoemission spectroscopy.