title: The complex interface chemistry of thin-film silicon/zinc oxide solar cell structures.
abstract: The interface between solid-phase crystallized phosphorous-doped polycrystalline silicon (poly-Si(n(+))) and aluminum-doped zinc oxide (ZnO:Al) was investigated using spatially resolved photoelectron emission microscopy. We find the accumulation of aluminum in the proximity of the interface. Based on a detailed photoemission line analysis, we also suggest the formation of an interface species. Silicon suboxide and/or dehydrated hemimorphite have been identified as likely candidates. For each scenario a detailed chemical reaction pathway is suggested. The chemical instability of the poly-Si(n(+))/ZnO:Al interface is explained by the fact that SiO2 is more stable than ZnO and/or that H2 is released from the initially deposited a-Si:H during the crystallization process. As a result, Zn (a deep acceptor in silicon) is "liberated" close to the silicon/zinc oxide interface presenting the inherent risk of forming deep defects in the silicon absorber. These could act as recombination centers and thus limit the performance of silicon/zinc oxide based solar cells. Based on this insight some recommendations with respect to solar cell design, material selection, and process parameters are given for further knowledge-based thin-film silicon device optimization.
authors.affiliation: Renewable Energies, Helmholtz-Zentrum Berlin für Materialien und Energie, Hahn-Meitner-Platz 1, D-14109 Berlin, Germany. marcus.baer@helmholtz-berlin.de.
authors.forename: D
authors.initials: D
authors.lastname: Gerlach
authors.forename: M
authors.initials: M
authors.lastname: Wimmer
authors.forename: R G
authors.initials: RG
authors.lastname: Wilks
authors.forename: R
authors.initials: R
authors.lastname: Félix
authors.forename: F
authors.initials: F
authors.lastname: Kronast
authors.forename: F
authors.initials: F
authors.lastname: Ruske
authors.forename: M
authors.initials: M
authors.lastname: Bär