title: Suppression of Thermally Induced Fullerene Aggregation in Polyfullerene-Based Multiacceptor Organic Solar Cells.
abstract: A novel main-chain polyfullerene, poly[fullerene-alt-2,5-bis(octyloxy)terephthalaldehyde] (PPC4), is investigated for its hypothesized superior morphological stability as an electron-accepting material in organic photovoltaics relative to the widely used fullerene phenyl-C61-butyric acid methyl ester (PCBM). When mixed with poly(3-hexylthiophene-2,5-diyl) (P3HT), PPC4 affords low-charge-generation yields because of poor intermixing within the blend. The adoption of a multiacceptor system, by introducing PCBM into the P3HT:polyfullerene blend, was found to lead to a 3-fold enhancement in charge generation, affording power conversion efficiencies very close to that of the prototypical P3HT:PCBM binary control. Upon thermal stressing and in contrast to the P3HT:PCBM binary, photovoltaic devices based on the multiacceptor system demonstrated significantly improved stability, outperforming the control because of suppression of the PCBM migration and aggregation processes responsible for rapid device failure. We rationalize the influence of the fullerene miscibility and its implications on the device performance in terms of a thermodynamic model based on Flory-Huggins solution theory. Finally, the potential universal applicability of this approach for thermal stabilization of organic solar cells is demonstrated, utilizing an alternative low-band-gap polymer-donor system.
authors.affiliation: ZAE Bayern , Auf AE, GBau 16, 1 OG Fürther Strasse 250, 90429 Nürnberg, Germany.|Belectric OPV GmbH , Landgrabenstrasse 94, 90443 Nürnberg, Germany.
authors.forename: Simon A
authors.identifier: http://orcid.org/0000-0002-3613-5666
authors.initials: SA
authors.lastname: Dowland
authors.affiliation: Institute of Materials for Electronics and Energy Technology, Friedrich-Alexander-University of Erlangen-Nürnberg , Martensstrasse 7, 91058 Erlangen, Germany.|Instituto de Telecomunicações, Instituto Superior Técnico , Avenida Rovisco Pais, P-1049-001 Lisboa, Portugal.
authors.forename: Michael
authors.initials: M
authors.lastname: Salvador
authors.affiliation: Institute of Materials for Electronics and Energy Technology, Friedrich-Alexander-University of Erlangen-Nürnberg , Martensstrasse 7, 91058 Erlangen, Germany.
authors.forename: José Darío
authors.initials: JD
authors.lastname: Perea
authors.affiliation: Institute of Materials for Electronics and Energy Technology, Friedrich-Alexander-University of Erlangen-Nürnberg , Martensstrasse 7, 91058 Erlangen, Germany.
authors.forename: Nicola
authors.initials: N
authors.lastname: Gasparini
authors.affiliation: Institute of Materials for Electronics and Energy Technology, Friedrich-Alexander-University of Erlangen-Nürnberg , Martensstrasse 7, 91058 Erlangen, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Langner
authors.affiliation: Belectric OPV GmbH , Landgrabenstrasse 94, 90443 Nürnberg, Germany.
authors.forename: Sambatra
authors.initials: S
authors.lastname: Rajoelson
authors.affiliation: CNRS, UMR5254, Université Pau et Pays Adour, Institut des Sciences Analytiques et de Physico-Chimie pour l'Environnement et les Matériaux , 64053 Pau, France.
authors.forename: Hasina H
authors.identifier: http://orcid.org/0000-0002-8039-995X
authors.initials: HH
authors.lastname: Ramanitra
authors.affiliation: Department of Chemistry and Pharmacy & Interdisciplinary Center for Molecular Materials, Friedrich-Alexander-University Erlangen-Nürnberg , 91054 Erlangen, Germany.
authors.forename: Benjamin D
authors.initials: BD
authors.lastname: Lindner
authors.affiliation: Institute of Materials for Electronics and Energy Technology, Friedrich-Alexander-University of Erlangen-Nürnberg , Martensstrasse 7, 91058 Erlangen, Germany.
authors.forename: Andres
authors.initials: A
authors.lastname: Osvet
authors.affiliation: Institute of Materials for Electronics and Energy Technology, Friedrich-Alexander-University of Erlangen-Nürnberg , Martensstrasse 7, 91058 Erlangen, Germany.
authors.forename: Christoph J
authors.initials: CJ
authors.lastname: Brabec
authors.affiliation: CNRS, UMR5254, Université Pau et Pays Adour, Institut des Sciences Analytiques et de Physico-Chimie pour l'Environnement et les Matériaux , 64053 Pau, France.
authors.forename: Roger C
authors.initials: RC
authors.lastname: Hiorns
authors.affiliation: ZAE Bayern , Auf AE, GBau 16, 1 OG Fürther Strasse 250, 90429 Nürnberg, Germany.
authors.forename: Hans-Joachim
authors.initials: HJ
authors.lastname: Egelhaaf
keywords: fullerene aggregation; main-chain polyfullerenes; multi acceptor composite blend; organic photovoltaics; thermal stability