ISBN 978-3-8439-1119-1

978-3-8439-1119-1, Reihe Ingenieurwissenschaften

Mahdi Mahajeri
Strukturbildung und Leitfähigkeit nanopartikulärer ITO-Schichten

195 Seiten, Dissertation Universität Erlangen-Nürnberg (2013), Softcover, A5

Zusammenfassung / Abstract

The production of nearly all transparent and conductive films for the application in electronics is based on polycrystalline indium tin oxide (ITO). The conventional ITO films, that are commonly made by physical or chemical vapor deposition and used in many applications such as OLEDs, displays or solar cells, are relatively expensive due to the high material and fabrication costs. In contrast, the development of ”printable electronics“ based on nanoparticles promises a significant cost reduction. This approach allows to link the advantages of printing methods, namely high printing output on large areas e.g. in the case of roll-to-roll process and the benefit of inorganic nanoparticles such as ITO. The thesis in hand focuses on the influence of disperse properties of ITO dispersions on the structure formation as well as the influence of structure formation and post treatment (such as annealing under different atmospheres or laser irradiation) on the optical and electrical properties of nanoparticulate ITO films. The investigations that start with the characterization of the crystalline structure of ITO nanoparticles via X-ray diffraction followed by a survey of the dispersion stability and film morphology by using dynamic light scattering and scanning electron microscopy reveals that the morphology of the ITO films is basically determined by the particle size distribution as well as stability of the dispersion and the drying kinetics of disperse phase to solid film. The analysis of the electrical conductivity of ITO films is performed by van der Pauw method, four point probe and temperature dependent impedance spectroscopy which indicates a direct correlation between the structure formation and electrical conductivity of the ITO films. In addition information about the charge transport mechanisms and the impact of post treatment on electrical conductivity will be provided. The final part of this work highlights the characterization of ITO nanoparticles pretreated under different conditions and ITO films made of them by using photoluminescence spectroscopy as well as transmissions spectroscopy. Thereby the correlation between the defect structure and the optical band gap of the ITO nanoparticles will be the subject of discussion. The results indicate the existence of an indirect excitation of electrons from valence band via donator band to conducting band beside the direct excitation of electrons from valence band to conducting band.