Light absorbing polymers for organic solar cells

Organic solar cell efficiencies are currently increasing rapidly and we are now poised to enter the commercial phase, with impending market introduction of the first prototypes based on organic bulk heterojunction devices fabricated from solution. Central to these device efficiency improvements are the development of new photoactive semiconducting donor and acceptor materials, designed at the molecular level to optimise both absorption of the long wavelength region of the solar spectrum and generation of high cell voltages. This presentation will examine some of the key design strategies to control the molecular orbital energy levels and microstructure of donor polymer semiconductors and illustrate with examples and their characterisation. Specifically, the systematic reduction of the bandgap in a series of bridged ladder type indenofluorene1 copolymers, in combination with the progressive lowering of the HOMO energy level will be shown.