Fullerene-Functionalized Donor-Acceptor Block Copolymers through Etherification as Stabilizers for Bulk Heterojunction Solar Cells

A new synthetic method for the covalent linking of fullerenes to polymers is introduced. The Bingel-reaction was used to prepare bromine-functionalized fullerene building blocks that could be covalently linked to hydroxyl groups of model copolymers by the cesium carbonate promoted Williamson ether synthesis. Subsequently, block copolymers with a second block based on styrene and hydroxystyrene or hydroxyethyl methacrylate could be synthesized with a poly(3-hexylthiophene)-TEMPO macro-initiator through NMRP. Fullerene derivatives were linked to these polymers in a controlled manner and donor-acceptor block copolymers with high fullerene contents of near 50 wt % were achieved.