Electronic properties of organic/metal interfaces

Conjugated organic materials are the promising class of materials for the application in new electronic and opto-electronic devices. The successful realization of highly efficient organic light emitting devices with oligomers and polymers as active electroluminescent layers has lead to a large number of investigations on such systems, the key point being to find means of increasing efficiency and performance of the devices. Intrinsically present in light emitting devices are interfaces, and it appears that the structural and electronic properties of those are of uttermost importance for the device quality. In the present work, ultraviolet and X-ray photoelectron spectroscopy, plus related surface sensitive experimental methods, were used to investigate the electronic properties of interfaces between conjugated organic materials (based on para-phenylene) and various metals. The observed interactions between the two different kinds of materials ranged from physisorption (aluminum and samarium), to the formation of new covalent bonds (calcium and a thiophene containing polymer) and charge transfer (doping) for alkali and alkaline-earth metals. (author)