Vinyl-type polynorbornenes with pendant PCBM: a novel acceptor for organic solar cells

Vinyl addition homo- and copolymerization of norbornene monomer (M1) functionalized with a PCBM moiety using a Pd(II) catalyst in combination with a 1-octene chain transfer agent efficiently produces polynorbornenes with side-chain PCBM groups. Characterization by NMR spectroscopy and elemental analysis reveals that the copolymers constitute a well-defined polymer structure with controlled incorporation of M1. Although the homopolymer is insoluble in organic solvents, the copolymers containing 62 mol% (P2) and 50 mol% (P3) of the PCBM moiety are soluble in chlorinated solvents such as o-dichlorobenzene. The bulk-heterojunction organic photovoltaic devices fabricated based on the P3HT:P3 blends show that P3 can adequately function as an electron acceptor, leading to a cell with a power conversion efficiency of 1.5%, which is outstanding among the polymeric rivals.