Triphenylamine and Carbazole-Based Hole Transporting Materials - and their Applications in Organic Field-Effect Transistors

摘要

Hole transporting materials based on π-conjugated organic compounds have alreadybeen the focus of intense research and investigation. Nevertheless, the charge transportmechanism occurring in such materials and its relation to the device stability in oxidizingatmosphere remains not fully clear. It has been demonstrated many times that the stabilityissue for p-type organic materials is one of the key features for their application in organicfield-effect transistors.In a conjoint work with the Evonik Degussa Creavis, research were lead to develop aseries of novel polymeric compounds usable as semiconducting layers of organicfield-effect transistors (OFETs) e.g. for printed radio frequency identification tags (RFIDTags) being processed and working under ambient conditions.In this regard, arylamine-based aromatic materials such as triphenylamine- orcarbazole-type polymers constitute ideal candidates for such applications due to theirgood environmental stability and OFET properties coupled with an easy processability ofthe polymeric materials.In chapter 2, a series of six main chain polytriphenylamines (PTPAs) with different alkylsubstituants and aromatic systems will be described. Chapter 3 deals with different N-arylsubstituted 3,6-polycarbazoles and their use as active layer in OFETs. At last, highercondensed aromatic systems based on the phenazine unit comprising model compoundsas well as the corresponding polymers are presented in chapter 4. In each chapter, thekey reactions are depicted including history, mechanism and the application for ourapproach. Additionally, a short introduction presents the state-of-the-art for the mentionedclasses of compounds.All the materials synthesized during this work were intensively analysed by spectroscopicmethods and most of them tested as semiconducting layer in OFET devices in order todetermine the influence of certain structural factors on the intrinsic electronic properties ofthe compounds. The stability problem has been intensively addressed and discussed withthe goal to provide a better understanding of the oxidation/degradation mechanism takingplace in OFET devices while operating.