Fullerene-based polymers for photovoltaic applications

Hasina H. Ramanitra1,  Simon A. Dowland2,  Graham E. Morse3,  Hugo Santos Silva4,  Didier Bégué5,  Thomas Chassé6,  Andreas Distler2,  Roger C. Hiorns7
1EPCP, IPREM (UMR-5254), Université de Pau et des Pays de l’Adour, 2 avenue Président Angot, France; Institut für Physikalische und Theoretische Chemie, Eberhard Karls Universität Tübingen, Auf der Morgenstelle 18 Tübingen, Germany;, 2Belectric OPV GmbH , Landgrabenstr. 94, 90443 Nürnberg, Germany;, 3Merck Chemicals Ltd., Chilworth Technical Centre, University Parkway, SO16 7QD, Southampton, United Kingdom;, 4EPCP, IPREM (UMR-5254), Université de Pau et des Pays de l’Adour, 2 avenue Président Angot; Institut für Physikalische und Theoretische Chemie, Eberhard Karls Universität Tübingen, Auf der Morgenstelle 18 Tübingen, Germany; ECP, IPREM (UMR-5254), Université de Pau et des Pays de l’Adour, 2 avenue Président Angot, France;, 5ECP, IPREM (UMR-5254), Université de Pau et des Pays de l’Adour, 2 avenue Président Angot, France;, 6Institut für Physikalische und Theoretische Chemie, Eberhard Karls Universität Tübingen, Auf der Morgenstelle 18 Tübingen, Germany;, 7CNRS, EPCP, IPREM (UMR-5254), 2 avenue Président Angot, 64053 Pau, Cedex, France.

Abstract

Polymer-based organic solar cells (OPVs) are promising sources of renewable energy due to their facile, low cost production, and formable nature [1]. OPVs exploit composites of n-and p-type materials. Although numerous p-type conjugated polymers have been prepared [2], this is not the case for n-type materials [3]. Due to its electronic properties and high electron mobility, small molecule C60 derivatives are widely used in large scale OPVs. However, the morphological properties of fullerene derivatives decrease device stabilities as C60 easily undergoes self-aggregation during OPV use [4]. The processibility of C60 can be improved by incorporating it into a polymer [5].

The aim of this work is to introduce fullerene-based polymers for photovoltaic applications, and present new synthetic routes to main-chain oligo- and polyfullerenes. Novel polyfullerenes were prepared with novel facile synthetic routes where C60 is exploited as a comonomer. The polymers were characterized by NMR, FTIR, UV-Visible, GPC and TG-DTA techniques. The materials were tested in OPV devices and showed an improved OPV thermal stability under annealing condition at different temperatures. To study the morphology/stability relationship, thin films of the active layer blends were annealed at 100, 120 and 140 °C and the changes in morphology were monitored by UV-visible spectroscopy and optical microscopy. The experimental data suggest that the use of the new fullerene-compounds enhance the thermal stability of the active layer.

The research leading to these results has received funding from the Region Aquitaine, under agreement 2012 FULLINC and from the European Union Seventh Framework Program FP7/2011 under grant agreement ESTABLIS no. 290022.

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