Print Email Facebook Twitter Charge transport in disordered organic field-effect transistors Title Charge transport in disordered organic field-effect transistors Author Meijer, E.J. Contributor Klapwijk, T.M. (promotor) Faculty Applied Sciences Date 2003-06-20 Abstract In this thesis we study charge transport in organic semiconductors. We do this by focusing on the physical characterization of disordered organic field-effect transistors. It will be made clear that the disorder in the polymer films is crucial for the interpretation of the data. The field-effect transistor geometry allows variation of the charge carrier density in the semiconductor, without the presence of counter ions. Therefore, the transistor allows a rather clean study of the charge transport in organic semiconductors as a function of the charge carrier density and temperature. In the experiments we find that the organic transistors are in several respects not comparable to silicon MOSFETs. Therefore, in this thesis we redefine and re-evaluate basic transistor parameters, such as the threshold voltage, the field-effect mobility, the contact resistance and the dopant density. Subsequently, we study the charge transport as a function of charge density, temperature and electric field, giving insight into the charge transport mechanism. Based on our observations we propose as the main charge transport mechanism: multiphonon hopping of polaronic charge carriers in a Gaussian density of states. We investigate the electrical stability of the polymer layer in metal-insulator-semiconductor diodes, where we determine and analyse the dopant density changes as a function of oxygen and light exposure. The presence of contact resistances in the transistors is addressed by analysing the scaling behavior of the electrical characteristics as a function of the transistor channel length, and an empirical relation between the contact resistance and the charge carrier mobility in the polymer layer is observed. Finally, we discuss why typically only unipolar transistor behavior is observed experimentally, and we demonstrate ambipolar transistor behavior in organic field-effect transistors based on blends of organic semiconductors and on low band gap organic semiconductors. Subject organic semiconductorfield-effect transistorcharge transportmodellingpolymers To reference this document use: http://resolver.tudelft.nl/uuid:6a2b93f3-4ef4-4363-8b2f-440e0a6d01e1 Publisher Optima Grafische Communicatie, Rotterdam ISBN 90-6734-306-4 Part of collection Institutional Repository Document type doctoral thesis Rights (c) 2003 E.J. Meijer Files PDF as_meijer_20030620.pdf 2.51 MB Close viewer /islandora/object/uuid:6a2b93f3-4ef4-4363-8b2f-440e0a6d01e1/datastream/OBJ/view