Poly(Δ4,4′-dicyclopenta[2,1-b:3,4-b′]dithiophene-co-3,4-ethylenedioxythiophene): Electrochemically generated low band gap conducting copolymers

A low HOMO-LUMO gap, alkene bridged bis-bithiophene (Δ4,4′-dicyclopenta [2,1-b:3,4-b′]dithiophene) has been copolymerized with electron rich 3,4-ethylenedioxythiophene, to produce copolymers with reduced band gaps and enhanced conductivities. Electrochemical band gaps as low as 0.1 eV have been observed, but maximum conductivities were only ca. 0.3 mS cm−1. Poor matching of the HOMO energies of the two components, together with cross-conjugation at the alkene bridge appear to limit charge carrier mobilities. These results provide further evidence that the use of donor and acceptor moieties to decrease band gaps leads to materials with decreased charge carrier mobilities due to charge localization.