Bispyridinium-phenylene-based copolymers: low band gap n-type alternating copolymers

Abstract

Bispyridinium-phenylene-based conjugated donor–acceptor copolymers were synthesized by a Stille cross-coupling and cyclization sequence. These polyelectrolytes are freely soluble in organic solvents and display broad optical absorption bands that extend into the near-infrared region. They show ambipolar redox properties with high electron affinities (LUMO levels) of 3.9–4.0 eV as well as high degrees of electroactivity. When reduced (n-doped) these materials display in situ conductivities as high as 180 S/cm. The high conductivity is attributed to the planar structure that is enforced by the cyclic structures of the polymer. The electron affinities are compared to PCBM, a C₆₀ based n-type material and hence may find utility in photovoltaic devices.