Electronic Structure of Organic/Metal Interfaces Studied by UPS and Kelvin Probe

Abstract

ABSTRACTThe interfaces of organic materials with other solids play important roles in the function of various organic devices such as organic light-emitting diodes (OLEDs), spectral sensitization in photography, organic solar cells, and electrophotography. Also they should be important in future molecular devices, both in the central part of the device and at the connection with outside circuits. However, serious experimental examination of such interfaces has started only recently. In this talk we focus our attention on the organic/metal interfaces, and summarize our understanding about (1) the energy level alignment right at the interface, and (2) possible band bending within an organic layer, mainly using the techniques of UV photoemission spectroscopy (UPS) and Kelvin probe method. As for (1), the formation of electric dipole layer was observed in most organic/metal interfaces, and its origin is discussed. As for (2), recent examination of the existence/absence of band bending in ultrahigh vacuum will be reported. It is also pointed out that there can be much effects of (i) atmosphere at sample preparation and measurements, and (2) chemistry and interdiffusion at the interface.