A new copolymer, constituted by the regular alternation of a fluorene derivative with a 1,1-dioxothiophene moiety, has been synthesised via Suzuki coupling. The molecular, thermal, structural, and photophysical characterisations have been performed. The material showed two dimensional order, enhanced by annealing; molecular modelling calculations afforded a consistent structural model accounting for the optical data. In comparison with both polyfluorenes and 1,1-dioxothiophene oligomers the unusual photoluminescence quantum yields observed in solution and in the solid state can be related to a significant contribution of internal conversion to the deactivation process in solution, and the formation of intra-chain hydrogen-bonds, due to a peculiar chain conformation, in the solid state. LED devices based on this new copolymer showed the highest efficiency compared with similar copolymers containing both fluorene and 1,1-dioxothiophene functionalities.

A series of oligomers constituting alternating thiophene and fluorenone residues, designed to evaluate the effect upon both electronic properties and packing of the moiety sequence in the light of donor–acceptor concept, were synthesised and studied by cyclic voltammetry, optical spectroscopy, and XRD investigations into crystals, films, and powders. Moreover, ab initio calculations, based on Density Functional Theory, were carried out on selected molecules. A clear indication of close-packing induction by fluorenone in the oligomers, together with the factors determining the electrical and optical properties, are derived and presented. In the light of the performance of selected compounds in prototypes of p-type FET devices and bulk heterojunction solar cells, some general indications of chemical structure requirements for applications such as photovoltaic cells are described.