Supramolecular control of organic p/n-heterojunctions by complementary hydrogen bonding
The supramolecular structure of organic semiconductors (OSCs) is the key parameter controlling their performance in organic electronic devices, and thus methods for controlling their self-assembly in the solid state are of the upmost importance. Recently, we have demonstrated the co-assembly of p- and n-type organic semiconductors through a three-point hydrogen-bonding interaction, utilizing an electron-rich dipyrrolopyridine (P2P) heterocycle which is complementary to naphthalenediimides (NDIs) both in its electronic structure and H bonding motif. The hydrogen-bonding-mediated co-assembly between P2P donor and NDI acceptor leads to ambipolar co-crystals and provides unique structural control over their solid-state packing characteristics. In this paper we expand our discussion on the crystal engineering aspects of H bonded donor–acceptor assemblies, reporting three new single co-crystal X-ray diffraction structures and analyzing the different packing characteristics that arise from the molecular structures employed. Particular attention is given toward understanding the formation of the two general motifs observed, segregated and mixed stacks. Co-assembly of the donor and acceptor components into a single, crystalline material, allows the creation of ambipolar semiconductors where the mutual arrangement of p- and n-conductive channels is engineered by supramolecular design based on complementary H bonding.