title: A silver-free, reflective substrate electrode for electron extraction in top-illuminated organic photovoltaics.
abstract: The choice of metals suitable as the reflective substrate electrode for top-illuminated organic photovoltaics (OPVs) is extremely limited. Herein, we report a novel substrate electrode for this class of OPV architecture based on an Al | Cu | AlOx triple-layer structure, which offers a reflectivity comparable to that of Al over the wavelength range 400-900 nm, a work function suitable for efficient electron extraction in OPVs and high stability towards oxidation. In addition to demonstrating the advantage of this composite electrode over Al in model top-illuminated OPVs, we also present the results of a photoelectron spectroscopy study, which show that an oxidised 0.8 nm Al layer deposited by thermal evaporation onto an Al | Cu reflective substrate electrode is sufficient to block oxidation of the underlying Cu by air or during deposition of a ZnO1-x electron-transport layer. This is remarkable given that the self-limiting oxide thickness on Al metal is greater than 2 nm.
authors.affiliation: Department of Chemistry, University of Warwick, Gibbet Hill, Coventry CV4 7AL (UK).
authors.forename: Martin S
authors.initials: MS
authors.lastname: Tyler
authors.forename: Oliver S
authors.initials: OS
authors.lastname: Hutter
authors.forename: Marc
authors.initials: M
authors.lastname: Walker
authors.forename: Ross A
authors.initials: RA
authors.lastname: Hatton
keywords: aluminum; copper; organic photovoltaics; photoelectron spectroscopy; reflective electrodes