Lessons learnt with donor:acceptor photovoltaic blends: can they be applied to doped polymer systems?

The question of how free charges are generated in donor:acceptor blends requires consideration that they are typically comprised of a complex phase morphology where intermixed and relatively phase-pure domains of the donor and acceptor co-exist. The local arrangement of the donor and acceptor plays thereby a decisive role in the fate of photogenerated electron-hole pairs –whether they dissociate to free charges or geminately recombine– as we demonstrate on a series of donor polymer:fullerenes binaries by combining 2D-NMR, time-resolved ultra-fast spectroscopy and detailed structural data. Our insights are important as similar considerations apply to other blends, such as semiconductor:dopant binaries that lead to highly conductive systems. We discuss how the spatial arrangement affects charge transport, and provide a tentative picture of the complex correlation of structure and electronic landscape towards the understanding of organic photovoltaics and doped, conducting plastics.