title: Unveiling the Hybrid n-Si/PEDOT:PSS Interface.
abstract: We investigated the buried interface between monocrystalline n-type silicon (n-Si) and the highly conductive polymer poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (
  PSS), which is successfully applied as a hole selective contact in hybrid solar cells. We show that a post-treatment of the polymer films by immersion in a suitable solvent reduces the layer thickness by removal of excess material. We prove that this post-treatment does not affect the functionality of the hybrid solar cells. Through the thin layer we are probing the chemical structure at the n-Si/
  PSS interface with synchrotron-based hard X-ray photoelectron spectroscopy (HAXPES). From the HAXPES data we conclude that the Si substrate of a freshly prepared hybrid solar cell is already oxidized immediately after preparation. Moreover, we show that even when storing the sample in inert gas such as, e.g., nitrogen the n-Si/SiOx/
  PSS interface continues to further oxidize. Thus, without further surface treatment, an unstable Si suboxide will always be present at the hybrid interface.
authors.affiliation: Institute of Nano-architectures for Energy Conversion, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH , Hahn-Meitner-Platz 1, 14109 Berlin, Germany.|Christiansen Research Group, Max-Planck-Institute for the Science of Light , Günther-Scharowsky-Straße 1, 91058 Erlangen, Germany.
authors.forename: Sara
authors.initials: S
authors.lastname: Jäckle
authors.affiliation: Energy Materials in-Situ Laboratory Berlin (EMIL), Helmholtz-Zentrum Berlin für Materialien und Energie GmbH , Albert-Einstein-Straße 15, 12489 Berlin, Germany.|Institute for Nanospectroscopy, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH , Albert-Einstein-Straße 15, 12489 Berlin, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Liebhaber
authors.affiliation: Energy Materials in-Situ Laboratory Berlin (EMIL), Helmholtz-Zentrum Berlin für Materialien und Energie GmbH , Albert-Einstein-Straße 15, 12489 Berlin, Germany.|Institute for Nanospectroscopy, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH , Albert-Einstein-Straße 15, 12489 Berlin, Germany.
authors.forename: Jens
authors.initials: J
authors.lastname: Niederhausen
authors.affiliation: Christiansen Research Group, Max-Planck-Institute for the Science of Light , Günther-Scharowsky-Straße 1, 91058 Erlangen, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Büchele
authors.affiliation: Renewable Energy, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH , Hahn-Meitner-Platz 1, 14109 Berlin, Germany.
authors.forename: Roberto
authors.initials: R
authors.lastname: Félix
authors.affiliation: Energy Materials in-Situ Laboratory Berlin (EMIL), Helmholtz-Zentrum Berlin für Materialien und Energie GmbH , Albert-Einstein-Straße 15, 12489 Berlin, Germany.|Renewable Energy, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH , Hahn-Meitner-Platz 1, 14109 Berlin, Germany.
authors.forename: Regan G
authors.initials: RG
authors.lastname: Wilks
authors.affiliation: Energy Materials in-Situ Laboratory Berlin (EMIL), Helmholtz-Zentrum Berlin für Materialien und Energie GmbH , Albert-Einstein-Straße 15, 12489 Berlin, Germany.|Renewable Energy, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH , Hahn-Meitner-Platz 1, 14109 Berlin, Germany.|Institut für Physik und Chemie, Brandenburgische Technische Universität Cottbus-Senftenberg , Platz der Deutschen Einheit 1, 03046 Cottbus, Germany.
authors.forename: Marcus
authors.initials: M
authors.lastname: Bär
authors.affiliation: Energy Materials in-Situ Laboratory Berlin (EMIL), Helmholtz-Zentrum Berlin für Materialien und Energie GmbH , Albert-Einstein-Straße 15, 12489 Berlin, Germany.|Institute for Nanospectroscopy, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH , Albert-Einstein-Straße 15, 12489 Berlin, Germany.|Fachbereich Physik, Freie Universität Berlin , Arnimallee 14, 14195 Berlin, Germany.
authors.forename: Klaus
authors.initials: K
authors.lastname: Lips
authors.affiliation: Institute of Nano-architectures for Energy Conversion, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH , Hahn-Meitner-Platz 1, 14109 Berlin, Germany.|Christiansen Research Group, Max-Planck-Institute for the Science of Light , Günther-Scharowsky-Straße 1, 91058 Erlangen, Germany.|Fachbereich Physik, Freie Universität Berlin , Arnimallee 14, 14195 Berlin, Germany.
authors.forename: Silke
authors.initials: S
authors.lastname: Christiansen
keywords: conducting polymers; device stability; hard X-ray photoelectron spectroscopy; hybrid materials; inorganic/organic; interface; solar cells