Speaker:Ronald Osterbacka,Abo Akademi University
Time:Thursday,9:30a.m.,28th March
Place:A718

Abstract:
We have extended the analytical framework of the charge extraction by linearly increasing voltage (CELIV) theory taking the effect of built-in voltage, diffusion and band-bending into account. By doing so we have been able to extend the CELIV into new regimes, namely for metal-insulator-metal structures, doped semiconductors and for metal-insulator-semiconductor structures. We have used the new regimes of CELIV as in-device characterization techniques to clarify important device physical parameters. We have derived analytical expressions describing the effective reduction of the built-in voltage and the (effective) open-circuit voltage providing means to quantify and distinguish various mechanisms for contact related effects in solar cells.
The surface recombination velocity, describing the quality of the contact interface, is a key parameter in obtaining an increased understanding of the kinetics taking place at contacts in thin-film devices. We show how to use MIS-CELIV to determine surface recombination velocities at selective and/or blocking contacts in thin-film devices, allowing us to directly estimating the dynamics at selective contacts.
Bio:
Professor Ronald ?sterbacka received his PhD in Physics in 1999 from ?bo Akademi. During his PhD he spent one year at the University of Utah under the guidance of Prof. Z. Valy Vardeny. ?sterbacka was an Academy of Finland Post Doctoral Research fellow (2000-2003) and Academy Research fellow (2004) before taking up the position as Full Professor of physics in 2005. His research interests are electro-optical properties of disordered organic semiconductors and novel devices for paper electronics, and have published more than 190 articles and book chapters since 1996. ?sterbacka has submitted three patent applications on ion-modulated transistors. He is the editor-in-chief for the IoP journal Flexible and Printed Electronics. Ronald ?sterbacka is the director of the Center for Functional Materials since 2011 and an elect member of the Swedish Academy of Engineering Sciences in Finland and Finnish Society for the Science and Letters. ?sterbacka has been active in arranging numerous conferences, most notably he was the chairman for the main conference on Synthetic Metals, ICSM2014 (www.icsm2014.fi) held in Turku June 30th to July 5th, 2014 gathering 600 scientists from all over the world.