UHV surface science as powerful tool to unravel principles and processes in hybrid perovskites
Selina Olthof a
a Universität zu Köln, Luxemburgerstrasse 116, Köln, 50939, Germany
Proceedings of Perovskite Thin Film Photovoltaics (ABXPV17)
València, Spain, 2017 March 1st - 2nd
Organizers: Henk Bolink and David Cahen
Invited Speaker, Selina Olthof, presentation 087
Publication date: 18th December 2016

In recent years, the interest in hybrid organic - inorganic perovskites rose at a rapid pace due to their tremendous success in the field of photovoltaics. In addition to the thin film properties of the active layer, the performance of optoelectronic devices strongly depends on the appropriate energetic alignment between the active- and adjacent layers. In order to choose adequate transport materials for the increasingly complex hybrid perovskite compositions in a non-trial-and-error fashion, it is important to understand how the induced changes in band gap relate to shifts in the valence and/or conduction band.

In this talk, I will discuss recent findings regarding measurements of the electronic structure of various hybrid perovskites, covering lead as well as tin based systems and a variety of halogens. Hereby, I will combine reports from literature with our own results based on UV-, inverse, and x-ray photoelectron spectroscopy measurements (UPS/IPES/XPS). Furthermore, using these surface sensitive techniques, not only the energetic values can be extracted but the alignment at interfaces between different layers can be probed in-situ as well by a stepwise film preparation.

Looking at the bottom contact, it became increasingly obvious in the last year that the substrate can have a strong influence on the stability of the adjacent perovskite film and that chemical interactions, band bending, and interface dipole formation play an important role. I will show that the nature of the substrate not only determines the energetic alignment but can create gap states and influence film formation and crystallinity, all of which makes the investigation of the interface to the substrate a highly relevant topic for current studies.

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