Conjugated materials for organic electronic devices : photoelectron spectroscopy studies

Abstract: Conjugated materials have attracted great attention since the discovery of high conductivity in donor and acceptor doped polyacetylene over two decades ago. The discoveries mentioned below caused, however, that the interest begun to shift towards their pristine semi-conducting state. It was largely due to the electronic properties suitable for electronics applications such as field-effect transistors (FET), light emitting devices or photovoltaic cells Enhancement of device performance required continued intensive research in materials development. Thus research in this area resulted in the interactive overlap of traditionally separated disciplines, such as synthesis of materials, molecular based electronics and advanced materials characterization. One of methods, which turned out to be a very suitable for the examination of physical and chemical properties of conjugated materials is photoelectron spectroscopy. The complementary exploitation of high resolution XPS, high quality UPS valence band spectroscopy and the results of quantum chemical calculations enabled to address many particular aspects related to basic electronic properties of conjugated materials as well as application oriented problems.This thesis includes the work focused on experimental studies of the electronic properties of conjugated materials by means of photoelectron spectroscopy. The thesis includes also the results of quantum chemical calculations carried out for the sake of comparison with the experiments as an aid in proper interpretation of experimental results. Particular investigations concern the electronic structure of novel derivatives of commonly applied polymers design to improve their performance in organic FETs, the studies on the electronic structure of the recently synthesized oligomers, which are potential candidates for high performance FETs and the detailed analysis of the role of counter ion on the properties of widely applied polymeric blend: poly(3,4-ethylenedioxythiophene) (PEDT) mixed with poly(styrenesulfonate) (PSS), PEDOT/PSS.