Background

In this chapter, the chemical and electronic structure of the interfaces between low work function metals and prototypical conjugated oligomers and polymers, appropriate for polymer LEDs, which have been studied over the past several years, are discussed. One of the underlying themes in these discussions is aimed at illustrating the combined experimental–theoretical approach, modelling the initial stages of the interface formation corresponding to the deposition of the metal onto the polymer surface, which has proven to be a very fruitful practice, yielding more than the simple sum of the individual parts. Following the description of the pertinent experimental sample preparation procedures, the examples are arranged in an order convenient for developing certain themes in the logic of the descriptions of the physical phenomena. More detail is supplied in the first examples, whereas less is supplied in subsequent examples, essentially pointing out differences. Also, an order has been chosen for presentation which minimizes the necessity of repetition of certain aspects.

From the experimental standpoint, the chemical and electronic structures of the surfaces of thin films of the conjugated materials are first studied in their pristine state, in order to generate surface electronic band structure parameters for input into device performance models. Then these surfaces are studied as metal atoms are slowly deposited, as the early stages for formation of the metallic overlayer develops. Two surface-sensitive techniques are used, each of which directly represents somewhat different but related aspects of the electronic structure of the polymer.