Supramolecular n/p-heterojunction photosystems with antiparallel redox gradients in electron- and hole-transporting pathways.

Lessons from nature call for supramolecular n/p-heterojunctions with oriented multicolored antiparallel redox gradients (OMARG-SHJs) as "ideal" photosystems. Their design combines advantages of bilayer and bulk n/p-heterojunction (BHJ) solar cells for the directional separation of photogenerated charges before recombination can occur. Although conceptually attractive, OMARG-SHJs have remained beyond reach because of unresolved challenges in synthetic organic and supramolecular chemistry. Here we report the first OMARG-SHJs with two-component redox gradients in both the electron- and hole-transporting pathways. They were obtained by zipper assembly of stacks of red naphthalenediimide (NDI) electron donors along strings of oligophenylethynyl hole acceptors on top of yellow NDI electron acceptors along p-oligophenyl hole donors. The presence of both gradients is shown to be essential for achieving photoinduced charge separation over very long distances.